Articles de revues : « Atrioventricular coupling »

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Sjöberg, Pia, Ellen Ostenfeld, Erik Hedström, Håkan Arheden, Ronny Gustafsson, Shahab Nozohoor et Marcus Carlsson. « Changes in left and right ventricular longitudinal function after pulmonary valve replacement in patients with Tetralogy of Fallot ». American Journal of Physiology-Heart and Circulatory Physiology 318, n^o 2 (1 février 2020) : H345—H353. http://dx.doi.org/10.1152/ajpheart.00417.2019.

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Timing and indication for pulmonary valve replacement (PVR) in patients with repaired Tetralogy of Fallot (rToF) and pulmonary regurgitation (PR) are uncertain. To improve understanding of pumping mechanics, we investigated atrioventricular coupling before and after surgical PVR. Cardiovascular magnetic resonance was performed in patients ( n = 12) with rToF and PR > 35% before and after PVR and in healthy controls ( n = 15). Atrioventricular plane displacement (AVPD), global longitudinal peak systolic strain (GLS), atrial and ventricular volumes, and caval blood flows were analyzed. Right ventricular (RV) AVPD and RV free wall GLS were lower in patients before PVR compared with controls ( P < 0.0001; P < 0.01) and decreased after PVR ( P < 0.0001 for both). Left ventricular AVPD was lower in patients before PVR compared with controls ( P < 0.05) and decreased after PVR ( P < 0.01). Left ventricular GLS did not differ between patients and controls ( P > 0.05). Right atrial reservoir volume and RV stroke volume generated by AVPD correlated in controls ( r = 0.93; P < 0.0001) and patients before PVR ( r = 0.88; P < 0.001) but not after PVR. In conclusion, there is a clear atrioventricular coupling in patients before PVR that is lost after PVR, possibly because of loss of pericardial integrity. Impaired atrioventricular coupling complicates assessment of ventricular function after surgery using measurements of longitudinal function. Changes in atrioventricular coupling seen in patients with rToF may be energetically unfavorable, and long-term effects of surgery on atrioventricular coupling is therefore of interest. Also, AVPD and GLS cannot be used interchangeably to assess longitudinal function in rToF. NEW & NOTEWORTHY There is a clear atrioventricular coupling in patients with Tetralogy of Fallot (ToF) and pulmonary regurgitation before surgical pulmonary valve replacement (PVR) that is lost after operation, possibly because of loss of pericardial integrity. The impaired atrioventricular coupling complicates assessment of ventricular function after surgery when using measurements of longitudinal function. Left ventricular atrioventricular plane displacement (AVPD) found differences between patients and controls and changes after PVR that longitudinal strain could not detect. This indicates that AVPD and strain cannot be used interchangeably to assess longitudinal function in repaired ToF.

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Vîjîiac, Aura, Alina Ioana Scărlătescu, Ioana Gabriela Petre, Cristian Vîjîiac et Radu Gabriel Vătășescu. « Three-Dimensional Combined Atrioventricular Coupling Index—A Novel Prognostic Marker in Dilated Cardiomyopathy ». Biomedicines 12, n^o 2 (28 janvier 2024) : 302. http://dx.doi.org/10.3390/biomedicines12020302.

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Atrioventricular coupling has recently emerged as an outcome predictor. Our aim was to assess, through three-dimensional (3D) echocardiography, the role of the left atrioventricular coupling index (LACI), right atrioventricular coupling index (RACI) and a novel combined atrioventricular coupling index (CACI) in a cohort of patients with dilated cardiomyopathy (DCM). One hundred twenty-one consecutive patients with DCM underwent comprehensive 3D echocardiographic acquisitions. LACI was defined as the ratio between left atrial and left ventricular 3D end-diastolic volumes. RACI was defined as the ratio between right atrial and right ventricular 3D end-diastolic volumes. CACI was defined as the sum of LACI and RACI. Patients were prospectively followed for death, heart transplant, nonfatal cardiac arrest and hospitalization for heart failure. Fifty-five patients reached the endpoint. All three coupling indices were significantly more impaired in patients with events, with CACI showing the highest area under the curve (AUC = 0.66, p = 0.003). All three indices were independent outcome predictors when tested in multivariable Cox regression (HR = 2.62, p = 0.01 for LACI; HR = 2.58, p = 0.004 for RACI; HR = 2.37, p = 0.01 for CACI), but only CACI showed an incremental prognostic power over traditional risk factors such as age, left ventricular strain, right ventricular strain and mitral regurgitation severity (likelihood ratio χ2 test = 28.2, p = 0.03). CACI assessed through 3D echocardiography, reflecting both left and right atrioventricular coupling, is an independent predictor of adverse events in DCM, yielding an incremental prognostic power over traditional risk factors.

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Sengupta, Partho P., et Jagat Narula. « À LA Mode Atrioventricular Mechanical Coupling ». JACC : Cardiovascular Imaging 7, n^o 1 (janvier 2014) : 109–11. http://dx.doi.org/10.1016/j.jcmg.2013.12.001.

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Gourdie, R. G., N. J. Severs, C. R. Green, S. Rothery, P. Germroth et R. P. Thompson. « The spatial distribution and relative abundance of gap-junctional connexin40 and connexin43 correlate to functional properties of components of the cardiac atrioventricular conduction system ». Journal of Cell Science 105, n^o 4 (1 août 1993) : 985–91. http://dx.doi.org/10.1242/jcs.105.4.985.

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Electrical coupling between heart muscle cells is mediated by specialised regions of sarcolemmal interaction termed gap junctions. In previous work, we have demonstrated that connexin42, a recently identified gap-junctional protein, is present in the specialised conduction tissues of the avian heart. In the present study, the spatial distribution of the mammalian homologue of this protein, connexin40, was examined using immunofluorescence, confocal scanning laser microscopy and quantitative digital image analysis in order to determine whether a parallel distribution occurs in rat. Connexin40 was detected by immunofluorescence in all main components of the atrioventricular conduction system including the atrioventricular node, atrioventricular bundle, and Purkinje fibres. Quantitation revealed that levels of connexin40 immunofluorescence increased along the axis of atrioventricular conduction, rising over 10-fold between atrioventricular node and atrioventricular bundle and a further 10-fold between atrioventricular bundle and Purkinje fibres. Connexin40 and connexin43, the principal gap-junctional protein of the mammalian heart, were co-localised within atrioventricular nodal tissues and Purkinje fibres. By applying a novel photobleach/double-labelling protocol, it was demonstrated that connexin40 and connexin43 are co-localised in precisely the same Purkinje fibre myocytes. A model, integrating data on the spatial distribution and relative abundance of connexin40 and connexin43 in the heart, proposes how myocyte-type-specific patterns of connexin isform expression account for the electrical continuity of cardiac atrioventricular conduction.

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Spitzer, K. W., N. Sato, H. Tanaka, L. Firek, M. Zaniboni et W. R. Giles. « Electrotonic modulation of electrical activity in rabbit atrioventricular node myocytes ». American Journal of Physiology-Heart and Circulatory Physiology 273, n^o 2 (1 août 1997) : H767—H776. http://dx.doi.org/10.1152/ajpheart.1997.273.2.h767.

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Electrotonic effects of electrically coupling atrioventricular (AV) nodal cells to each other and to real and passive models of atrial and ventricular cells were studied using a technique that does not require functional gap junctions. Membrane potential was measured in each cell using suction pipettes. Mutual entrainment of two spontaneously firing AV nodal cells was achieved with a junctional resistance (Rj) of 500 M omega, which corresponds to only 39 junctional channels, assuming a single-channel conductance of 50 pS. Coupling of AV nodal and atrial cells at Rj of 50 M omega caused hyperpolarization of the nodal cell, decreasing its action potential duration and either slowing or blocking diastolic depolarization in the AV node myocyte. Opposite changes occurred in the atrial action potential. When AV nodal and ventricular cells were coupled at Rj of 50 M omega, nodal diastolic potential was markedly hyperpolarized and diastolic depolarization was completely blocked with little change in ventricular diastolic potential. However, coupling did elicit marked changes in the action potential duration of both cells, with prolongation in the nodal cell and shortening in the ventricular cell. Nodal maximum upstroke velocity was increased by both atrial and ventricular coupling, as expected from the hyperpolarization that occurred. With an Rj of 50 M omega, spontaneous firing was blocked in all single AV nodal pacemaker cells during coupling to a real or passive model of an atrial or ventricular cell. These results demonstrate that action potential formation and waveform in a single AV nodal cell is significantly affected by electrical coupling to other myocytes.

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Terlizzi, Vito Di, Roberta Barone, Nicola Di Nunno, Gianmarco Alcidi, Natale Daniele Brunetti et Massimo Iacoviello. « The Atrioventricular Coupling in Heart Failure : Pathophysiological and Therapeutic Aspects ». Reviews in Cardiovascular Medicine 25, n^o 5 (14 mai 2024) : 169. http://dx.doi.org/10.31083/j.rcm2505169.

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Pham, Caroline, Svitlana Podliesna, Arie Verkerk, Rianne Wolswinkel, Noelia Muñoz-Martín, Marieke Veldkamp, Leander Beekman et al. « TNNI3K delays atrioventricular conduction and reduces connexin-45 gap junctional coupling ». Journal of Molecular and Cellular Cardiology 173 (décembre 2022) : 83–84. http://dx.doi.org/10.1016/j.yjmcc.2022.08.167.

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Hernández Burgos, Paula M., et Angel López-Candales. « Changes in Mitral Annular Ascent with Worsening Echocardiographic Parameters of Left Ventricular Diastolic Function ». Scientifica 2016 (2016) : 1–4. http://dx.doi.org/10.1155/2016/6303815.

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Background. While the mitral annular plane systolic excursion (MAPSE) has been suggested as a surrogate measurement of left ventricular ejection fraction, less is known about the relative value of mitral annular ascent (MAa).Methods. Our database was queried for complete transthoracic echocardiograms performed for any clinical indication. Baseline echocardiographic measurements were compared to determine any correlation between MAa and traditional Echo-Doppler echocardiographic measures to characterize left ventricular diastolic dysfunction (LVDD).Results. Patients with normal LV diastolic function were younger (41±13years) than patients with LVDD (stage 1:61±13years; stage 2:57±14years; and stage 3:66±17years;p=0.156). LV ejection fraction decreased in patients with stage 2 LVDD (63±17%) and was further reduced in patients with stage 3 LVDD (28±21;p=0.003).Discussion. While a vigorous MAa excursion was seen in patients with stage 1 LVDD, MAa significantly decreased in stage 2 and stage 3 LVDD patients. Our results highlight the importance of atrioventricular coupling, as MAa motion seems to reflect changes in left atrial pressure. Additional studies are now required to better examine atrioventricular interactions and electromechanical coupling that might improve our assessment of LV diastolic function.

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Mazgalev, Todor, Kent Mowrey, Igor Efimov, Gerard J. Fahy, David Van Wagoner, Yuanna Cheng et Patrick J. Tchou. « Mechanism of atrioventricular nodal facilitation in rabbit heart : role of proximal AV node ». American Journal of Physiology-Heart and Circulatory Physiology 273, n^o 4 (1 octobre 1997) : H1658—H1668. http://dx.doi.org/10.1152/ajpheart.1997.273.4.h1658.

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The phenomenon of atrioventricular (AV) nodal “facilitation,” described in traditional “black box”-functional studies, implies enhanced AV nodal dromotropic function. We investigated the role of atrial prematurities in the modulation of the nodal cellular responses in the mechanism of AV nodal facilitation. Atrial and His (H) bundle electrograms and microelectrode recordings from proximal AV nodal cells were analyzed in 15 superfused rabbit AV node preparations. The pacing protocol consisted of 30 basic beats (S1; coupling interval S1-S1= 300 ms) followed by a facilitating prematurity (S2; coupling intervals S1-S2of 300, 200, 150, and 130 ms) followed by the test beat (S3; coupling interval S2-S3scanned in 5-ms steps). Conduction curves (S2-H2vs. S1-S2, S3-H3vs. S2-S3, and S3-H3vs. H2-S3) were constructed. Facilitation (i.e., shortening of S3-H3when S1-S2was shortened) was demonstrated in all preparations using the H2-S3( P < 0.001) but not the S2-S3format. Microelectrode recordings revealed a causal relationship between the improved proximal AV nodal cellular responses in facilitation and the prolonged S2-S3interval. There was no evidence for enhanced nodal dromotropic function directly resulting from the introduction of the facilitating beats. Thus facilitation is based on inherent cycle-length-dependent properties of the AV node during application of a complex pacing protocol and primarily reflects the uncontrolled modulation of the proximal cellular response.

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Masè, Michela, Leon Glass, Marcello Disertori et Flavia Ravelli. « The AV synchrogram : A novel approach to quantify atrioventricular coupling during atrial arrhythmias ». Biomedical Signal Processing and Control 8, n^o 6 (novembre 2013) : 1008–16. http://dx.doi.org/10.1016/j.bspc.2013.01.004.

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Apostol, Adrian, Nicolae Albulescu, Stela Iurciuc, Mircea Iurciuc, Carina Bogdan et Mihaela Viviana Ivan. « Difference in Cardiac Electrical Vulnerability Between Passive Silicone Steroid Eluting Lead vs. Active Screw-in Lead ». Materiale Plastice 56, n^o 4 (30 décembre 2019) : 968–72. http://dx.doi.org/10.37358/mp.19.4.5293.

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Patients with total atrioventricular block are of particular interest and prone to severe prognosis unless treated with emergency cardiac pacing. We evaluated different types of leads and their impact on the myocardium, according to the fixation type and pacing method.. A pacemaker patient has a different depolarization pattern and a single chamber pacemaker, has by definition, an intracardiac desynchronization and a different electro-mechanical coupling activity. The presence of late potentials is an independent prognosis factor for cardiac death and electrical vulnerability, especially after myocardial infarction(MI). Late potentials recorded as magnitude vector are the expresion of late depolarization of the surrounding tissue and represent the morfological substrate for reentry. Thus, the incidence of late potentials after pacemaker implant, represents the expresion of electrical vulnerability of the stimulated right ventricular myocardium. In order to deeply study the parameters of magnitude vectors, we noticed the appearance of late potentials during the transitory stimulation in acute atrioventricular block and a restoration of vector normal parameters, after conduction recovery and sinus rhythm conversion.

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Pezel, Theo, Bharath Ambale Venkatesh, Henrique Doria De Vasconcellos, Yoko Kato, Mahsima Shabani, Eric Xie, Susan R. Heckbert et al. « Left Atrioventricular Coupling Index as a Prognostic Marker of Cardiovascular Events : The MESA Study ». Hypertension 78, n^o 3 (septembre 2021) : 661–71. http://dx.doi.org/10.1161/hypertensionaha.121.17339.

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Both left atrial and left ventricular functional parameters influence the prognosis of patients with cardiovascular diseases. This study aimed to investigate the prognostic value of a novel left atrioventricular coupling index (LACI) in a population without history of cardiovascular diseases at baseline. Participants of the Multi-Ethnic Study of Atherosclerosis who underwent a baseline cardiovascular magnetic resonance study were analyzed. LACI was defined by the ratio of the left atrial end-diastolic volume divided by the left ventricular end-diastolic volume. Cox proportional hazard models were used to evaluate the association between LACI and atrial fibrillation, heart failure, coronary heart disease death, and hard cardiovascular disease defined by myocardial infarction, resuscitated cardiac arrest, fatal and nonfatal stroke, or coronary heart disease death. Among the 4124 participants (61.5±10.1 years, 47.4% men), 1074 cardiovascular events were observed (mean follow-up, 13.0±3.2 years). Greater LACI was independently associated with atrial fibrillation (hazard ratio, 1.86 [95% CI, 1.69–2.04]), heart failure (hazard ratio, 1.50 [95% CI, 1.38–1.62]), hard cardiovascular disease (1.23 [95% CI, 1.13–1.34]), and coronary heart disease death (hazard ratio, 1.29 [95% CI, 1.15–1.45]; all P <0.0001). After adjustment for traditional cardiovascular risk factors, LACI showed significant improvement in model discrimination and reclassification compared with currently used standard models to predict outcomes. LACI is a strong predictor for the incidence of heart failure, atrial fibrillation, hard cardiovascular disease, and coronary heart disease death. LACI has incremental prognostic value to predict cardiovascular events over traditional risk factors and better discrimination and reclassification power compared with individual left atrial or left ventricular parameters.

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Wright, S., S. Mak, Z. Sasson, T. Gray, S. Esfandiari, A. Chelvanathan, F. Fuchs, W. Chan et J. Goodman. « Effect of Submaximal Exercise on Atrioventricular Coupling and Left Ventricular Filling in Healthy Athletes ». Canadian Journal of Cardiology 29, n^o 10 (octobre 2013) : S146—S147. http://dx.doi.org/10.1016/j.cjca.2013.07.213.

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Billette, J. « Atrioventricular nodal activation during periodic premature stimulation of the atrium ». American Journal of Physiology-Heart and Circulatory Physiology 252, n^o 1 (1 janvier 1987) : H163—H177. http://dx.doi.org/10.1152/ajpheart.1987.252.1.h163.

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To study the intranodal origin of the functional properties of the atrioventricular node, progressive changes in nodal cell activation time and cycle length occurring during complete sequences of periodic premature stimulation of the atrium were determined for 419 nodal cells recorded in 11 isolated rabbit heart preparations. The conduction time in proximal nodal cells including the N cells increased only at very short coupling intervals. Conduction time in the distal node (NH and H cells) first increased and then decreased with increasing prematurity. The major fraction of the basic and premature delays developed between N and NH cell activation, a period devoid of upstrokes. The effective and functional refractory periods were related to the minimum intervals between successive upstrokes at the node entrance and outlet, respectively. These results suggest that the cycle-length dependency of nodal conduction is the result of complex changes in propagation time occurring at three levels in the node, whereas the effective and functional refractory periods reflect reactivation limits of cells located at the node entrance and outlet, respectively.

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Hu, N., et B. B. Keller. « Relationship of simultaneous atrial and ventricular pressures in stage 16-27 chick embryos ». American Journal of Physiology-Heart and Circulatory Physiology 269, n^o 4 (1 octobre 1995) : H1359—H1362. http://dx.doi.org/10.1152/ajpheart.1995.269.4.h1359.

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Ventricular filling is determined by a dynamic balance between atrial and ventricular load and function. The embryonic cardiovascular system undergoes simultaneous growth and morphogenesis at the cellular, tissue, and organ levels to match the embryo's geometrically increasing metabolic demands. As part of our long-term investigation of atrial/ventricular coupling during primary cardiac morphogenesis, we defined the relationship between simultaneous atrial and ventricular pressures in the stage 16-27 white Leghorn chick embryo. We measured atrial and ventricular blood pressures with servo-null micropressure systems and sampled analog waveforms digitally at 500 Hz. Peak atrial pressure increased geometrically from 0.38 +/- 0.03 to 1.21 +/- 0.17 mmHg, while ventricular end-diastolic pressure increased linearly from 0.18 +/- 0.03 to 0.55 +/- 0.04 mmHg. The passive and active mean pressure gradients increased from 0.23 +/- 0.04 and 0.20 +/- 0.03 mmHg at stage 16 to 0.52 +/- 0.10 and 0.62 +/- 0.11 mmHg at stage 27, respectively. The atrioventricular pressure gradients were similar for stages 16, 18, and 21, then increased to stage 27. This diastolic pressure gradient identifies the atrioventricular orifice and developing endocardial cushions as a site of flow resistance that may influence both ventricular filling and chamber morphogenesis.

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Yin, Lili, Jiajie Mei, Jianli Dong, Xiaofeng Qu et Yinong Jiang. « Association of sodium intake with adverse left atrial function and left atrioventricular coupling in Chinese ». Journal of Hypertension 41, n^o 1 (7 novembre 2022) : 159–70. http://dx.doi.org/10.1097/hjh.0000000000003317.

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Pezel, T., J. G. Dillinger, S. Toupin, R. Mirailles, D. Logeart, A. Cohen-Solal, T. Gonçalves, J. Lima, V. Bousson et P. Henry. « Left atrioventricular coupling index assessed using cardiac CT as a prognostic marker of cardiovascular death ». Archives of Cardiovascular Diseases Supplements 15, n^o 3 (juin 2023) : 264. http://dx.doi.org/10.1016/j.acvdsp.2023.04.044.

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Pezel, T., J. G. Dillinger, S. Toupin, S. Miraillesx, D. Logeart, A. Cohen Solal, A. Unger et al. « Left atrioventricular coupling index assessed using cardiac CT as a prognostic marker of cardiovascular death ». Archives of Cardiovascular Diseases 117, n^o 1 (janvier 2024) : S66—S67. http://dx.doi.org/10.1016/j.acvd.2023.10.118.

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Kyriakou, Stavroula, Andreas Lubig, Cilia A. Sandhoff, Yasmin Kuhn et Stefan Jockenhoevel. « Influence of Diameter and Cyclic Mechanical Stimulation on the Beating Frequency of Myocardial Cell-Laden Fibers ». Gels 9, n^o 9 (23 août 2023) : 677. http://dx.doi.org/10.3390/gels9090677.

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Atrioventricular block (AVB) is a severe disease for pediatric patients. The repetitive operations needed in the case of the pacemaker implantation to maintain the electrical signal at the atrioventricular node (AVN) affect the patient’s life quality. In this study, we present a method of biofabrication of multi-cell-laden cylindrical fibrin-based fibers that can restore the electrical signal at the AVN. We used human umbilical vein smooth muscle cells (HUVSMCs), human umbilical vein endothelial cells (HUVECs) and induced pluripotent stem cell cardiomyocytes (iPSC-CMs) cultivated either statically or dynamically to mimic the native AVN. We investigated the influence of cell composition, construct diameter and cyclic stretch on the function of the fibrin hydrogels in vitro. Immunohistochemistry analyses showed the maturity of the iPSC-CMs in the constructs through the expression of sarcomeric alpha actinin (SAA) and electrical coupling through Connexin 43 (Cx43) signal. Simultaneously, the beating frequency of the fibrin hydrogels was higher and easy to maintain whereas the concentration of iPSC-CMs was higher compared with the other types of cylindrical constructs. In total, our study highlights that the combination of fibrin with the cell mixture and geometry is offering a feasible biofabrication method for tissue engineering approaches for the treatment of AVB.

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Meijler, F. L., et M. J. Janse. « Morphology and electrophysiology of the mammalian atrioventricular node ». Physiological Reviews 68, n^o 2 (1 avril 1988) : 608–47. http://dx.doi.org/10.1152/physrev.1988.68.2.608.

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The AV node of those mammalian species in which it has been thoroughly investigated (rabbit, ferret, and humans) consists of various cell types: transitional cells, midnodal (or typical nodal cells), lower nodal cells, and cells of the AV bundle. There are at least two inputs to the AV node, a posterior one via the crista terminalis and an anterior one via the interatrial septum, where atrial fibers gradually merge with transitional cells. The role of a possible third input from the left atrium has not been investigated. Since the transition from atrial fibers to nodal fibers is gradual, it is very difficult to define the "beginning" of the AV node, and gross measurements of AV nodal length may be misleading. Histologically, the "end" of the AV node is equally difficult to define. At the site where macroscopically the AV node ends, at the point where the AV bundle penetrates into the membranous septum, typical nodal cells intermingle with His bundle cells. A conspicuous feature, found in all species studied, is the paucity of junctional complexes, most marked in the midnodal area. The functional counterpart of this is an increased coupling resistance between nodal cells. An electrophysiological classification of the AV nodal area, based on transmembrane action potential characteristics during various imposed atrial rhythms (rapid pacing, trains of premature impulses), into AN (including ANCO and ANL), N, and NH zones has been described by various authors for the rabbit heart. In those studies in which activation patterns, transmembrane potential characteristics, and histology have been compared, a good correlation has been found between AN and transitional cells, N cells and the area where transitional cells and cells of the beginning of the AV bundle merge with midnodal cells, and NH cells and cells of the AV bundle. Dead-end pathways correspond to the posterior extension of the bundle of lower nodal cells and to anterior overlay fibers. During propagation of a normal sinus beat, activation of the AN zone accounts for at least 25% of conduction time from atrium to His bundle, the small N zone being the main source of AV nodal delay. Cycle length-dependent conduction delay is localized in the N zone. Conduction block of premature atrial impulses can occur both in the N zone and in the AN zone, depending on the degree of prematurity. Several factors determining AV nodal conduction delay have been identified.(ABSTRACT TRUNCATED AT 400 WORDS)

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Rossano, Joseph W., et Anthony C. Chang. « Perioperative management of patients with poorly functioning ventricles in the setting of the functionally univentricular heart ». Cardiology in the Young 16, S1 (10 janvier 2006) : 47–54. http://dx.doi.org/10.1017/s1047951105002325.

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The patient with a functionally univentricular heart is at increased risk for ventricular dysfunction for a variety of reasons. At birth, the pulmonary and systemic circulations are in parallel, leading to pulmonary overcirculation and a volume-loaded functional ventricle. Significant atrioventricular valvar regurgitation, abnormal ventriculoarterial coupling, diastolic dysfunction, and altered ventricular geometry can also contribute to long-term ventricular dysfunction. These collected circumstances place the patient at increased risk for perioperative morbidity and mortality. We will discuss in this review the pathophysiology that leads to ventricular dysfunction at each stage of surgical palliation, as well as the strategies for perioperative management. In addition, we will highlight novel strategies for management of ventricular dysfunction.

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Dresel, Peter E., A. Ogbaghebriel et R. Abraham. « Electrophysiological effects of ethmozine in perfused rabbit hearts ». Canadian Journal of Physiology and Pharmacology 63, n^o 11 (1 novembre 1985) : 1418–22. http://dx.doi.org/10.1139/y85-233.

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His-bundle electrocardiography was used to evaluate the effects of ethmozine on cardiac conduction in isolated perfused rabbit hearts electrically driven at cycle lengths of 320 and 250 ms. There was no significant change in conduction until high concentrations of ethmozine were reached. His-Purkinje and atrioventricular (AV) nodal conduction were slowed significantly at 0.1 μg/mL and atrial conduction at 1.0 μg/mL. Conduction block occurred at 10.0 μg/mL in all the hearts treated. Effects of the drug (0.1 and 0.01 μg/mL) on conduction of extrasystoles were also studied in hearts driven at a basic cycle length of 270 ms. No significant change was observed in atrial conduction of extrasystoles throughout the coupling intervals tested at both concentrations. Ethmozine (0.01 and 0.1 μg/mL) caused slowing of His-Purkinje conduction of extrasystoles but the effect of the drug did not change as a function of the coupling interval. An interval-dependent increase in AV-nodal conduction time was observed, with the maximum slowing of conduction occurring at coupling intervals close to the effective refractory period of the AV node. AV-nodal functional refractory period was increased significantly by ethmozine (0.01 and 0.1 μg/mL). The effective refractory period was significantly increased only at the higher concentration.

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Joyner, Ronald W., Yang-Gan Wang, Ronald Wilders, David A. Golod, Mary B. Wagner, Rajiv Kumar et William N. Goolsby. « A spontaneously active focus drives a model atrial sheet more easily than a model ventricular sheet ». American Journal of Physiology-Heart and Circulatory Physiology 279, n^o 2 (1 août 2000) : H752—H763. http://dx.doi.org/10.1152/ajpheart.2000.279.2.h752.

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Tachycardias can be produced when focal activity at ectopic locations in either the atria or the ventricles propagates into the surrounding quiescent myocardium. Isolated rabbit atrioventricular nodal cells were coupled by an electronic circuit to a real-time simulation of an array of cell models. We investigated the critical size of an automatic focus for the activation of two-dimensional arrays made up of either ventricular or atrial model cells. Over a range of coupling conductances for the arrays, the critical size of the focus cell group for successful propagation was smaller for activation of an atrial versus a ventricular array. Failure of activation of the arrays at smaller focus sizes was due to the inhibition of pacing of the nodal cells. At low levels of coupling conductance, the ventricular arrays required larger sizes of the focus due to failure of propagation even when the focus was spontaneously active. The major differences between activation of the atrial and ventricular arrays is due to the higher membrane resistance (lower inward rectifier current) of the atrial cells.

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Pezel, T., B. Ambale Venkatesh, H. D. De Vasconcellos, Y. Kato, M. Shabani, E. G. Xie, S. R. Heckbert et al. « Left atrioventricular coupling index (LACI) as a prognostic marker : The multi-ethnic study of atherosclerosis (MESA) ». Archives of Cardiovascular Diseases Supplements 13, n^o 1 (janvier 2021) : 52. http://dx.doi.org/10.1016/j.acvdsp.2020.10.044.

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Pezel, T., B. Ambale Venkatesh, Y. Kato, H. D. De Vasconcellos, S. R. Heckbert, C. Wu, W. Post et al. « Left atrioventricular coupling index to predict incident heart failure : The Multi-Ethnic Study of Atherosclerosis (MESA) ». Archives of Cardiovascular Diseases Supplements 13, n^o 3 (juin 2021) : 239. http://dx.doi.org/10.1016/j.acvdsp.2021.04.005.

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Yin, Lili, Jiajie Mei, Yinong Jiang et Jianli Dong. « PS-C35-4 : ASSOCIATION OF SODIUM INTAKE WITH ADVERSE LEFT ATRIAL FUNCTION AND LEFT ATRIOVENTRICULAR COUPLING ». Journal of Hypertension 41, Suppl 1 (janvier 2023) : e480. http://dx.doi.org/10.1097/01.hjh.0000917808.69550.30.

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Dorveaux, L. D., N. Twidale, N. Robinson et A. M. Tonkin. « Computer algorithm for modeling transmission over one or two conduction pathways through AV node ». American Journal of Physiology-Heart and Circulatory Physiology 255, n^o 5 (1 novembre 1988) : H1247—H1253. http://dx.doi.org/10.1152/ajpheart.1988.255.5.h1247.

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The goal of this study was to develop and test models of conduction through the atrioventricular node, particularly to encompass possible transmission over multiple pathways. Output from the atrioventricular node was related to its input, the variable coupling interval of a single extrastimulus introduced to scan diastole during programmed atrial stimulation. Trials were performed three times in 15 patients after pacing for eight beats at 100 beats/min. Hyperbolic and exponential functions were used to model trial data. For conduction over a single pathway, the standard error of the estimate was less with the exponential than with the hyperbolic model. The preferred exponential model had the general form A2H2 = K1 + K2 exp(-A1A2/K3), with K1, K2, K3 being the parameters fitted. The algorithm describing transmission over two pathways minimized sums of squares of deviations from two such exponential functions, with potential "bifurcation" points between the functions being those farthest from the computed single curve of best fit. The model predicted (R2 greater than 0.90) that 43% of the trials showed single conduction pathways and the remaining 57% showed dual pathways. A cardiologist who independently examined the data discarded eight trials because of insufficient data or scatter and agreed with presence of two pathways and the point of discontinuity in plots in 81% of trials. The reasons for discordance were minor and thus the model was reasonably verified.

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Masè, M., M. Marini, M. Disertori et F. Ravelli. « Dynamics of AV coupling during human atrial fibrillation : role of atrial rate ». American Journal of Physiology-Heart and Circulatory Physiology 309, n^o 1 (1 juillet 2015) : H198—H205. http://dx.doi.org/10.1152/ajpheart.00726.2014.

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The causal relationship between atrial and ventricular activities during human atrial fibrillation (AF) is poorly understood. This study analyzed the effects of an increase in atrial rate on the link between atrial and ventricular activities during AF. Atrial and ventricular time series were determined in 14 patients during the spontaneous acceleration of the atrial rhythm at AF onset. The dynamic relationship between atrial and ventricular activities was quantified in terms of atrioventricular (AV) coupling by AV synchrogram analysis. The technique identified n: m coupling patterns ( n atrial beats in m ventricular cycles), quantifying their percentage, maximal length, and conduction ratio (= m/ n). Simulations with a difference-equation AV model were performed to correlate the observed dynamics to specific atrial/nodal properties. The atrial rate increase significantly affected AV coupling and ventricular response during AF. The shortening of atrial intervals from 185 ± 32 to 165 ± 24 ms ( P < 0.001) determined transitions toward AV patterns with progressively decreasing m/ n ratios (from conduction ratio = 0.34 ± 0.09 to 0.29 ± 0.08, P < 0.01), lower occurrence (from percentage of coupled beats = 27.1 ± 8.0 to 21.8 ± 6.9%, P < 0.05), and higher instability (from maximal length = 3.9 ± 1.5 to 2.8 ± 0.7 s, P < 0.01). Advanced levels of AV block and coupling instability at higher atrial rates were associated with increased ventricular interval variability (from 123 ± 52 to 133 ± 55 ms, P < 0.05). AV pattern transitions and coupling instability in patients were predicted, assuming the filtering of high-rate irregular atrial beats by the slow recovery of nodal excitability. These results support the role of atrial rate in determining AV coupling and ventricular response and may have implications for rate control in AF.

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Backhaus, Sören J., Johannes T. Kowallick, Thomas Stiermaier, Torben Lange, Alexander Koschalka, Jenny-Lou Navarra, Johannes Uhlig et al. « Atrioventricular mechanical coupling and major adverse cardiac events in female patients following acute ST elevation myocardial infarction ». International Journal of Cardiology 299 (janvier 2020) : 31–36. http://dx.doi.org/10.1016/j.ijcard.2019.06.036.

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Rein, Azaria J. J. T., Clare P. O'Donnell, Steven D. Colan et Gerald R. Marx. « Tissue velocity Doppler assessment of atrial and ventricular electromechanical coupling and atrioventricular time intervals in normal subjects ». American Journal of Cardiology 92, n^o 11 (décembre 2003) : 1347–50. http://dx.doi.org/10.1016/j.amjcard.2003.08.026.

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Pezel, T., P. Garot, S. Toupin, F. Sanguineti, T. Hovasse, T. Unterseeh, S. Champagne et al. « AI-based fully automated left atrioventricular coupling index as a prognostic marker in patients undergoing stress-CMR ». Archives of Cardiovascular Diseases Supplements 15, n^o 3 (juin 2023) : 256. http://dx.doi.org/10.1016/j.acvdsp.2023.04.025.

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Hadjseyd, C., A. Zaroui, M. Bézard, M. Kharoubi, S. Oghina, A. Galat, C. Chalard et al. « Contribution of the left atrioventricular coupling index in the prediction of atrial fibrillation in cardiac amyloidosis ATTR ». Archives of Cardiovascular Diseases 117, n^o 1 (janvier 2024) : S51. http://dx.doi.org/10.1016/j.acvd.2023.10.093.

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Pezel, T., P. Garot, S. Toupin, F. Sanguineti, T. Hovasse, T. Unterseeh, S. Champagne et al. « AI-based fully automated left atrioventricular coupling index as a prognostic marker in patients undergoing stress-CMR ». Archives of Cardiovascular Diseases 117, n^o 1 (janvier 2024) : S67—S68. http://dx.doi.org/10.1016/j.acvd.2023.10.119.

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Minajeva, Ave, Allen Kaasik, Kalju Paju, Enn Seppet, Anne-Marie Lompré, Vladimir Veksler et Renée Ventura-Clapier. « Sarcoplasmic reticulum function in determining atrioventricular contractile differences in rat heart ». American Journal of Physiology-Heart and Circulatory Physiology 273, n^o 5 (1 novembre 1997) : H2498—H2507. http://dx.doi.org/10.1152/ajpheart.1997.273.5.h2498.

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The relationships between the contractile characteristics and the sarcoplasmic reticulum (SR) function of rat atrial and ventricular trabeculae were compared. The isometric developed tension (DT) and the rates of contraction (+dT/d t) and relaxation (−dT/d t) normalized to cross-sectional area were 3.7, 2.2, and 1.8 times lower, respectively, in intact atrial strips compared with ventricular strips, whereas +dT/d t and −dT/d t(normalized to DT) were 2.3 and 2.8 times higher, respectively, in atria. Atria exhibited a maximal potentiation of DT after shorter rest periods than ventricles and a lower reversal for prolonged rest periods. Caffeine-induced tension transients in saponin-permeabilized fibers suggested that the Ca2+concentration released in atrial myofibrils reached a lower maximum and decayed more slowly than in ventricular preparations. However, the tension-time integrals indicated an equivalent capacity of sequestrable Ca2+ in SR from both tissues. In atrial, as in ventricular myocardium, the SR Ca2+ uptake was more efficiently supported by ATP produced by the SR-bound MM form of creatine kinase (CK; MM-CK) than by externally added ATP, suggesting a tight functional coupling between the SR Ca2+adenosinetriphosphatase (ATPase) and MM-CK. The maximal rate of oxalate-supported Ca2+ uptake was two times higher in atrial than in ventricular tissue homogenates. The SR Ca2+-ATPase 2a mRNA content normalized to 18S RNA was 38% higher in atria than in ventricles, whereas the amount of mRNA encoding the α-myosin heavy chain, calsequestrin, and the ryanodine receptor was similar in both tissues. Thus a lower amount of readily releasable Ca2+ together with a faster uptake rate may partly account for the shorter time course and lower tension development in intact atrial myocardium compared with ventricular myocardium.

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Dennis, D., K. Jacobson et L. Belardinelli. « Evidence of spare A1-adenosine receptors in guinea pig atrioventricular node ». American Journal of Physiology-Heart and Circulatory Physiology 262, n^o 3 (1 mars 1992) : H661—H671. http://dx.doi.org/10.1152/ajpheart.1992.262.3.h661.

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In normoxic, isolated perfused guinea pig hearts instrumented for measurement of atrioventricular nodal conduction time (AVCT), an analysis utilizing the irreversible A1-adenosine (Ado) antagonist, meta-1,3-phenylene diisothiocyanate xanthine amine cogener (m-DITC-XAC), a novel isothiocyanate derivative of 1,3-dialkylxanthine, was used to investigate whether spare A1-Ado receptors exist in the guinea pig atrioventricular (AV) node and the degree of amplification (reserve) between A1-Ado receptor occupancy and dromotropic response (e.g., AVCT slowing). The potency, dose dependency, and kinetic profile (time dependence of washout and washin) of m-DITC-XAC was determined and compared with those of known competitive (reversible) A1-Ado receptor antagonists. In the presence of m-DITC-XAC, Ado and N6-cyclopentyladenosine (CPA) produced submaximal dromotropic responses. In a series of 19 hearts, m-DITC-XAC caused 100% apparent antagonism of the effect of Ado on AVCT even after 60 min of washout. In contrast, greater than 90% of 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) and XAC-induced antagonism of the effect of Ado on AVCT dissipated within 35 min. Unlike XAC, which caused maximal attenuation of Ado's AVCT effect within 5 min and remained constant thereafter, m-DITC-XAC showed marked time- and concentration-dependent behavior. It was found that 5 min of 0.5 microM m-DITC-XAC pretreatment irreversibly inactivated 72% of the A1-Ado receptors mediating the dromotropic effect, and the estimated agonist equilibrium dissociation constant for CPA was 84 +/- 4 nM. The percent of spare A1-Ado receptors at the EC50 and extrapolated maximal S-H interval prolongation levels was 20 and 54%, respectively, and the reserve (coupling amplification) varied from 1 to 2.3 within the 0-50% maximal response range. In summary, m-DITC-XAC appears to specifically and irreversibly antagonize the negative dromotropic effect of Ado and CPA, and guinea pig AV nodal tissue possesses spare A1-Ado receptors.

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Pezel, T., B. Ambale Venkatesh, H. D. De Vasconcellos, Y. Kato, M. Shabani, E. G. Xie, S. R. Heckbert et al. « Incident heart failure prediction : left atrioventricular functional coupling index (LAFCI) from the multi-ethnic study of atherosclerosis (MESA) ». Archives of Cardiovascular Diseases Supplements 13, n^o 1 (janvier 2021) : 36–37. http://dx.doi.org/10.1016/j.acvdsp.2020.10.108.

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Pezel, T., B. Ambale Venkatesh, T. Quinaglia, S. R. Heckbert, Y. Kato, H. Doria De Vasconcellos, C. Wu et al. « Change in left atrioventricular coupling index to predict incident atrial fibrillation : The Multi-Ethnic Study of Atherosclerosis (MESA) ». Archives of Cardiovascular Diseases Supplements 13, n^o 3 (juin 2021) : 239–40. http://dx.doi.org/10.1016/j.acvdsp.2021.04.006.

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Pezel, T., B. A. Venkatesh, S. H. Heckbert, K. Yoko, H. D. De Vasconcellos, C. O. Wu, W. Post et al. « Change in left atrioventricular coupling index to predict hard cardiovascular disease : The Multi-Ethnic Study of Atherosclerosis (MESA) ». Archives of Cardiovascular Diseases Supplements 14, n^o 1 (janvier 2022) : 49. http://dx.doi.org/10.1016/j.acvdsp.2021.09.107.

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Berg, J., R. Jablonowski, D. Nordlund, S. Kopic, S. Bidhult, C. G. Xanthis, M. Saeed, K. Solem, H. Arheden et M. Carlsson. « Decreased atrioventricular plane displacement after acute myocardial infarction yields a concomitant decrease in stroke volume ». Journal of Applied Physiology 128, n^o 2 (1 février 2020) : 252–63. http://dx.doi.org/10.1152/japplphysiol.00480.2019.

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Acute myocardial infarction (AMI) can progress to heart failure, which has a poor prognosis. Normally, 60% of stroke volume (SV) is attributed to the longitudinal ventricular shortening and lengthening evident in the atrioventricular plane displacement (AVPD) during the cardiac cycle, but there is no information on how the relationship changes between SV and AVPD before and after AMI. Therefore, the aim of this study was to determine how SV depends on AVPD before and after AMI in two swine models. Serial cardiac magnetic resonance imaging was carried out before and 1–2 h after AMI in a microembolization model ( n = 12) and an ischemia-reperfusion model ( n = 14). A subset of pigs ( n = 7) were additionally imaged at 24 h and at 7 days. Cine and late gadolinium enhancement images were analyzed for cardiac function, AVPD measurements and infarct size estimation, respectively. AVPD decreased ( P < 0.05) in all myocardial regions after AMI, with a concomitant SV decrease ( P < 0.001). The ischemia-reperfusion model affected SV to a higher degree and had a larger AVPD decrease than the microembolization model (−29 ± 14% vs. −15 ± 18%; P < 0.05). Wall thickening decreased in infarcted areas ( P < 0.001), and A-wave AVPD remained unchanged ( P = 0.93) whereas E-wave AVPD decreased ( P < 0.001) after AMI. We conclude that AVPD is coupled to SV independent of infarct type but likely to a greater degree in ischemia-reperfusion infarcts compared with microembolization infarcts. AMI reduces diastolic early filling AVPD but not AVPD from atrial contraction. These findings shed light on the physiological significance of atrioventricular plane motion when assessing acute and subacute myocardial infarction. NEW & NOTEWORTHY The link between cardiac longitudinal motion, measured as atrioventricular plane displacement (AVPD), and stroke volume (SV) is investigated in swine after acute myocardial infarction (AMI). This cardiac magnetic resonance study demonstrates a close coupling between AVPD and SV before and after AMI in an experimental setting and demonstrates that this connection is present in ischemia-reperfusion and microembolization infarcts, acutely and during the first week. Furthermore, AVPD is equally and persistently depressed in infarcted and remote myocardium after AMI.

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Zakeri, Rosita, Gilles Moulay, Qiang Chai, Ozgur Ogut, Saad Hussain, Hiroyuki Takahama, Tong Lu et al. « 197 Left Atrial Remodelling and Atrioventricular Coupling in a Canine Model of Early Heart Failure with Preserved Ejection Fraction ». Heart 101, Suppl 4 (juin 2015) : A109.2—A110. http://dx.doi.org/10.1136/heartjnl-2015-308066.197.

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Demirkiran, Ahmet, Luuk Hopman, Irene M. Frenaij, Sonia Borodzicz-Jazdzyk, Sulayman El Mathari, Veronique Meijborg, Pranav Bhagirath et Marc Gotte. « THE INTERPLAY BETWEEN CMR-DERIVED LEFT ATRIOVENTRICULAR COUPLING AND ATRIAL REMODELING AND ABLATION OUTCOME IN PATIENTS WITH ATRIAL FIBRILLATION ». Journal of the American College of Cardiology 81, n^o 8 (mars 2023) : 1520. http://dx.doi.org/10.1016/s0735-1097(23)01964-2.

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Swift, Luther M., Morgan Burke, Devon Guerrelli, Marissa Reilly, Manelle Ramadan, Damon McCullough, Tomas Prudencio et al. « Age-dependent changes in electrophysiology and calcium handling : implications for pediatric cardiac research ». American Journal of Physiology-Heart and Circulatory Physiology 318, n^o 2 (1 février 2020) : H354—H365. http://dx.doi.org/10.1152/ajpheart.00521.2019.

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Rodent models are frequently employed in cardiovascular research, yet our understanding of pediatric cardiac physiology has largely been deduced from more simplified two-dimensional cell studies. Previous studies have shown that postnatal development includes an alteration in the expression of genes and proteins involved in cell coupling, ion channels, and intracellular calcium handling. Accordingly, we hypothesized that postnatal cell maturation is likely to lead to dynamic alterations in whole heart electrophysiology and calcium handling. To test this hypothesis, we employed multiparametric imaging and electrophysiological techniques to quantify developmental changes from neonate to adult. In vivo electrocardiograms were collected to assess changes in heart rate, variability, and atrioventricular conduction (Sprague-Dawley rats). Intact, whole hearts were transferred to a Langendorff-perfusion system for multiparametric imaging (voltage, calcium). Optical mapping was performed in conjunction with an electrophysiology study to assess cardiac dynamics throughout development. Postnatal age was associated with an increase in the heart rate (181 ± 34 vs. 429 ± 13 beats/min), faster atrioventricular conduction (94 ± 13 vs. 46 ± 3 ms), shortened action potentials (APD80: 113 ± 18 vs. 60 ± 17 ms), and decreased ventricular refractoriness (VERP: 157 ± 45 vs. 57 ± 14 ms; neonatal vs. adults, means ± SD, P < 0.05). Calcium handling matured with development, resulting in shortened calcium transient durations (168 ± 18 vs. 117 ± 14 ms) and decreased propensity for calcium transient alternans (160 ± 18- vs. 99 ± 11-ms cycle length threshold; neonatal vs. adults, mean ± SD, P < 0.05). Results of this study can serve as a comprehensive baseline for future studies focused on pediatric disease modeling and/or preclinical testing. NEW & NOTEWORTHY This is the first study to assess cardiac electrophysiology and calcium handling throughout postnatal development, using both in vivo and whole heart models.

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Germans, Tjeerd, Marco J. W. Götte, Robin Nijveldt, Marieke D. Spreeuwenberg, Aernout M. Beek, Jean G. F. Bronzwaer, Cees A. Visser, Walter J. Paulus et Albert C. van Rossum. « Effects of Aging on Left Atrioventricular Coupling and Left Ventricular Filling Assessed Using Cardiac Magnetic Resonance Imaging in Healthy Subjects ». American Journal of Cardiology 100, n^o 1 (juillet 2007) : 122–27. http://dx.doi.org/10.1016/j.amjcard.2007.02.060.

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LANGBERG, JONATHAN J., TRACY WONNELL, MICHAEL C. CHIN, WALTER FINKBEINER, MELVIN SCHEINMAN et PAUL STAUFFER. « Catheter Ablation of the Atrioventricular Junction Using a Helical Microwave Antenna : A Novel Means of Coupling Energy to the Endocardium ». Pacing and Clinical Electrophysiology 14, n^o 12 (décembre 1991) : 2105–13. http://dx.doi.org/10.1111/j.1540-8159.1991.tb06481.x.

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Zakeri, Rosita, Hiroyuki Takahama, Philip A. Araoz, Hon-Chi Lee et Margaret M. Redfield. « Alterations in Left Atrial Structure, Phasic Function and Atrioventricular Coupling Impact Cardiac Performance in Heart Failure with Preserved Ejection Fraction ». Journal of Cardiac Failure 20, n^o 8 (août 2014) : S71—S72. http://dx.doi.org/10.1016/j.cardfail.2014.06.204.

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Gunsaulus, Megan, Alejandra Bueno, Carley Bright, Katelyn Snyder, Nikkan Das, Craig Dobson, Mark DeBrunner et al. « The Use of Automated Atrial CMR Measures and a Novel Atrioventricular Coupling Index for Predicting Risk in Repaired Tetralogy of Fallot ». Children 10, n^o 2 (18 février 2023) : 400. http://dx.doi.org/10.3390/children10020400.

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Atrial size and function have been recognized as markers of diastolic function, and diastolic dysfunction has been identified as a predictor of adverse outcomes in repaired tetralogy of Fallot (rTOF). This was a retrospective single-center study with the objective of investigating the use of atrial measurements obtained via CMR for predicting outcomes in rTOF patients. Automated contours of the left and right atria (LA and RA) were performed. A novel parameter, termed the Right Atrioventricular Coupling Index (RACI), was defined as the ratio of RA end-diastolic volume to right ventricle (RV) end-diastolic volume. Patients were risk-stratified using a previously validated Importance Factor Score for the prediction of life-threatening arrhythmias in rTOF. Patients with a high-risk Importance Factor Score (>2) had a significantly larger minimum RA volume (p = 0.04) and RACI (p = 0.03) compared to those with scores ≤2. ROC analysis demonstrated RACI to be the best overall predictor of a high-risk Importance Factor Score (AUC 0.73, p = 0.03). Older age at the time of repair and a diagnosis of pulmonary atresia were associated with a larger RACI. Automated atrial CMR measurements are easily obtained from standard CMRs and have the potential to serve as noninvasive predictors of adverse outcomes in rTOF.

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Billette, Jacques, et Marie St-Vincent. « Functional origin of rate-induced changes in atrioventricular nodal conduction time of premature beats in the rabbit ». Canadian Journal of Physiology and Pharmacology 65, n^o 11 (1 novembre 1987) : 2329–37. http://dx.doi.org/10.1139/y87-369.

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The characteristics and origin of the rate-induced changes in atrioventricular nodal conduction time of premature beats (A2H2 intervals) were studied in isolated rabbit heart preparations. Increasing the basic driving rate during a periodic premature stimulation prolonged (a net inhibitory effect) and shortened (a net facilitatory effect) significantly (p < 0.01, n = 17) the A2H2 intervals associated with long and short recovery times (H1A2 intervals), respectively. The origin of these responses was sought for by analyzing interactions between facilitation and fatigue. When the fatigue developed at a fast basic rate was estimated from changes in conduction time of basic beats and subtracted from the corresponding A2H2 intervals, the calculated A2H2 intervals showed enhanced facilitation but no fatigue. When independently obtained fatigue and facilitation effects were added to the control A2H2 intervals for corresponding H1A2 intervals, resulting A2H2 intervals correlated strongly with the ones observed at the equivalent fast basic rate (r = 0.99, p < 0.001). Moreover, changes in the A2H2 intervals of premature beats tested with constant coupling intervals during 5-min fast rates were biphasic, confirming the overlapping and competition between facilitation and fatigue effects. Hence, rate-induced deviations of premature nodal conduction time from that predicted by changes in recovery time are consistent and result from the interaction between the overlapping effects produced by two independent, antagonist, and dynamically distinct nodal properties (facilitation and fatigue).

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Vijiiac, A. E., A. Scarlatescu, V. Verinceanu, C. Cojocaru, I. Petre, S. Onciul, M. Dorobantu et R. Vatasescu. « Three-dimensional left and right atrioventricular coupling indices as prognostic markers in heart failure with reduced ejection fraction ». European Heart Journal 43, Supplement_2 (1 octobre 2022). http://dx.doi.org/10.1093/eurheartj/ehac544.095.

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Abstract Background While left atrial and left ventricular functional parameters are established prognostic markers in heart failure (HF), recent studies suggest that parameters assessing the atrio-ventricular interaction are better predictors. Left atrioventricular coupling index (LACI) assessed with cardiac magnetic resonance is an emerging outcome predictor in HF patients, however its assessment by three-dimensional (3D) echocardiography hasn't been studied so far. Moreover, the role of the right atrioventricular coupling index (RACI) in HF remains to be established. Purpose We sought to evaluate the LACI, RACI and combined left and right atrioventricular coupling index (CACI) with 3D echocardiography in a cohort of patients with HF and reduced ejection fraction (HFrEF) and to assess their prognostic role. Methods We prospectively enrolled 60 consecutive patients with HFrEF in sinus rhythm, who underwent two dimensional and 3D echocardiographic acquisitions. LACI was calculated as the ratio between 3D left atrial and 3D left ventricular end-diastolic volumes. RACI was calculated as the ratio between 3D right atrial and 3D right ventricular end-diastolic volumes. CACI was defined as the sum between LACI and RACI. Patients were followed for major adverse cardiac events (MACE), defined as a composite endpoint of cardiac death or HF decompensation requiring hospitalization. Results After a mean follow-up of 19±9 months, 33 patients reached the endpoint. Patients with MACE had higher LACI (33.5±21.1% vs. 19.9±12.4%, p=0.003), higher RACI (33.6±23.6% vs. 20.8±13.8%, p=0.01) and higher CACI (67.0±38.0% vs. 40.7±24.4%, p=0.002) – suggestive of atrioventricular decoupling. In ROC analysis, CACI had the best AUC for event prediction (AUC=0.750, p=0.001, cut-off=42.8%, Sen=69.7%, Spe=77.7%), followed by LACI (AUC=0.745, p=0.001, cut-off=20.4%, Sen=72.7%, Spe=70.4%), and then RACI (AUC=0.717, p=0.004, cut-off=18.6%, Sen=75.8%, Spe=70.4%). In unadjusted Cox regression, all three atrioventricular coupling indices were predictors of MACE: HR=3.30 [95% CI, 1.52–7.14], p=0.002 for LACI, HR=4.54 [95% CI, 2.03–10.17], p<0.001 for RACI, HR=3.87 [95% CI, 1.82–8.23], p<0.001 for CACI. A multivariable model was constructed using well-established event predictors in HFrEF: age, global longitudinal strain of the left ventricle, global longitudinal strain of the right ventricular free wall and pulmonary artery systolic pressure. All three atrioventricular coupling indices remained independent predictors of MACE in multivariable regression: HR=3.11 [95% CI, 1.36–7.14], p=0.007 for LACI, HR=4.38 [95% CI, 1.84–10.41], p=0.001 for RACI, HR=3.98 [95% CI, 1.75–9.03], p=0.001 for CACI. Conclusion Greater 3D LACI, RACI and CACI, reflecting atrioventricular uncoupling, are all independent prognostic markers in HFrEF. Funding Acknowledgement Type of funding sources: None.

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Pezel, Theo, Bharath Ambale Venkatesh, Yoko Kato, Henrique Doria De Vasconcellos, Susan R. Heckbert, Colin O. Wu, Wendy S. Post et al. « Left Atrioventricular Coupling Index to Predict Incident Heart Failure : The Multi-Ethnic Study of Atherosclerosis ». Frontiers in Cardiovascular Medicine 8 (1 septembre 2021). http://dx.doi.org/10.3389/fcvm.2021.704611.

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Background: Although left atrial (LA) and left ventricular (LV) structural and functional parameters have independent prognostic value as predictors of heart failure (HF), the close physiological relationship between the LA and LV suggest that the assessment of LA/LV coupling could better reflect left atrioventricular dysfunction and be a better predictor of HF.Aim: We investigated the prognostic value of a left atrioventricular coupling index (LACI), measured by cardiovascular magnetic resonance (CMR), as well as change in LACI to predict incident HF in the Multi-Ethnic Study of Atherosclerosis (MESA).Materials and Methods: In the MESA, 2,250 study participants, free of clinically recognized HF and cardiovascular disease (CVD) at baseline, had LACI assessed by CMR imaging at baseline (Exam 1, 2000–2002), and 10 years later (Exam 5, 2010–2012). Left atrioventricular coupling index was defined as the ratio of LA to LV end-diastolic volumes. Univariable and multivariable Cox proportional hazard models were used to evaluate the associations of LACI and average annualized change in LACI (ΔLACI) with incident HF after adjustment for traditional MESA-HF risk factors. The incremental risk prediction was calculated using C-statistic, categorical net reclassification index (NRI) and integrative discrimination index (IDI).Results: Among the 2,250 participants (mean age 59.3 ± 9.3 years and 47.6% male participants), 50 incident HF events occurred over 6.8 ± 1.3 years after the second CMR exam. After adjustment, greater LACI and ΔLACI were independently associated with HF (adjusted HR 1.44, 95% CI [1.25–1.66] and adjusted HR 1.55, 95% CI [1.30–1.85], respectively; both p < 0.0001). Adjusted models for LACI showed significant improvement in model discrimination and reclassification compared to currently used HF risk score model for predicting HF incidence (C-statistic: 0.81 vs. 0.77; NRI = 0.411; IDI = 0.043). After adjustment, ΔLACI showed also significant improvement in model discrimination compared to the multivariable model with traditional MESA-HF risk factors for predicting incident HF (C-statistic: 0.82 vs. 0.77; NRI = 0.491; IDI = 0.058).Conclusions: In a multi-ethnic population, atrioventricular coupling (LACI), and coupling change (ΔLACI) are independently associated with incident HF. Both have incremental prognostic value for predicting HF events over traditional HF risk factors.

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Salgado‐Almario, Jussep, Yillcer Molina, Manuel Vicente, Antonio Martínez‐Sielva, Raúl Rodríguez‐García, Pierre Vincent, Beatriz Domingo et Juan Llopis. « ERG potassium channels and T‐type calcium channels contribute to the pacemaker and atrioventricular conduction in zebrafish larvae ». Acta Physiologica, 9 décembre 2023. http://dx.doi.org/10.1111/apha.14075.

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AbstractAimBradyarrhythmias result from inhibition of automaticity, prolonged repolarization, or slow conduction in the heart. The ERG channels mediate the repolarizing current IKr in the cardiac action potential, whereas T‐type calcium channels (TTCC) are involved in the sinoatrial pacemaker and atrioventricular conduction in mammals. Zebrafish have become a valuable research model for human cardiac electrophysiology and disease. Here, we investigate the contribution of ERG channels and TTCCs to the pacemaker and atrioventricular conduction in zebrafish larvae and determine the mechanisms causing atrioventricular block.MethodsZebrafish larvae expressing ratiometric fluorescent Ca2+ biosensors in the heart were used to measure Ca2+ levels and rhythm in beating hearts in vivo, concurrently with contraction and hemodynamics. The atrioventricular delay (the time between the start of atrial and ventricular Ca2+ transients) was used to measure impulse conduction velocity and distinguished between slow conduction and prolonged refractoriness as the cause of the conduction block.ResultsERG blockers caused bradycardia and atrioventricular block by prolonging the refractory period in the atrioventricular canal and in working ventricular myocytes. In contrast, inhibition of TTCCs caused bradycardia and second‐degree block (Mobitz type I) by slowing atrioventricular conduction. TTCC block did not affect ventricular contractility, despite being highly expressed in cardiomyocytes. Concomitant measurement of Ca2+ levels and ventricular size showed mechano‐mechanical coupling: increased preload resulted in a stronger heart contraction in vivo.ConclusionERG channels and TTCCs influence the heart rate and atrioventricular conduction in zebrafish larvae. The zebrafish lines expressing Ca2+ biosensors in the heart allow us to investigate physiological feedback mechanisms and complex arrhythmias.

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Articles de revues sur le sujet « Atrioventricular coupling »

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