Murphy C F, Lab M J, Horner S M, Dick D J, Harrison F G
British Heart Foundation Cardiac Arrhythmia Research Group, Department of Physiology, Charing Cross and Westminster Medical School, London, United Kingdom.
Am J Physiol. 1994 Nov;267(5 Pt 2):H1726-35. doi: 10.1152/ajpheart.1994.267.5.H1726.
Electrical and mechanical alternans have often been found to coexist. However, the factors controlling their interdependence are not known. In this study we measure regional electrical and mechanical activity during mechanical alternans to investigate this relationship. Mechanical alternans was induced by rapid atrial pacing in 18 anesthetized, open-chest pigs. Regional segmental contraction and monophasic action potential were measured in three areas of left ventricle using epicardial tripodal strain gauges and suction electrodes. Electrical alternans always accompanied pulsus alternans. The phase of electrical alternans was not related to any measure of regional mechanical activity but did show a constant discordant relation to peak ventricular pressure. This suggested that mechanically dependent changes in action potential duration (mechanoelectric feedback) may be important in modulation electrical alternans. In support of this, pulsus alternans simulated by clamping the proximal aorta on alternate beats was associated with electrical alternans comparable to that produced with rapid atrial pacing. Mechanoelectric feedback modulates regional electrophysiology in the intact heart and may be important in the generation of electrical alternans.
电交替和机械交替常被发现同时存在。然而，控制它们相互依存关系的因素尚不清楚。在本研究中，我们在机械交替期间测量局部电活动和机械活动，以研究这种关系。通过快速心房起搏在18只麻醉的开胸猪中诱发机械交替。使用心外膜三脚架应变仪和吸引电极在左心室的三个区域测量局部节段收缩和单相动作电位。电交替总是伴随着脉搏交替。电交替的相位与任何局部机械活动指标均无关，但与心室压力峰值始终呈现不一致的关系。这表明动作电位时程的机械依赖性变化（机电反馈）可能在调节电交替中起重要作用。支持这一观点的是，通过交替钳夹近端主动脉模拟的脉搏交替与电交替相关，与快速心房起搏产生的电交替相当。机电反馈调节完整心脏的局部电生理学，可能在电交替的产生中起重要作用。
