Horner S M, Murphy C F, Coen B, Dick D J, Harrison F G, Vespalcova Z, Lab M J
British Heart Foundation Cardiac Arrhythmia Research Group, Department of Physiology, Charing Cross and Westminster Medical School, London, England.
Circulation. 1996 Oct 1;94(7):1762-7. doi: 10.1161/01.cir.94.7.1762.
Heart rate variability is an important prognostic indicator for sudden death. An increased risk of sudden death and arrhythmia is associated with reduced heart rate variability in heart failure. In heart failure, there is also dilatation of the atria, which raises the prospect that there could be some physiological basis to possibly link heart rate variability with atrial dilatation. We therefore investigated whether sustained atrial stretch could modulate heart rate variability directly.
Pigs were anesthetized and their hearts exposed. A specially built device stretched the sinoatrial node before and after vagal section and then after administration of propranolol. Stretch of the sinoatrial node decreases heart rate variability in the following ways: The standard deviation of the beat-to-beat interval decreases (4.2 to 2.6 ms; P = .004), and the high-frequency components are reduced (control, 6.5 +/- 2.2 ms2, during stretch, 1.4 +/- 0.3 ms2, P = .003). After section of both vagi, the high-frequency components are reduced by stretch of the sinoatrial node (2.8 +/- 0.9 ms2 for control versus 1.2 +/- 0.3 ms2 during stretch; P = .05). Similarly, after both vagal section and beta-blockade, stretch of the sinoatrial node reduces the high-frequency components (10.6 +/- 3.5 ms2 for control verses 3.0 +/- 1.5 ms2 during stretch; P = .01).
We conclude that stretch of the sinoatrial node reduces high-frequency heart rate variability. This may account in part for the reduced heart rate variability seen in clinical conditions in which the right atrium is dilated, such as congestive cardiac failure.
心率变异性是猝死的重要预后指标。心力衰竭时心率变异性降低与猝死和心律失常风险增加相关。在心力衰竭中，心房也会扩张，这增加了心率变异性与心房扩张之间可能存在某种生理联系的可能性。因此，我们研究了持续性心房牵张是否能直接调节心率变异性。
将猪麻醉并暴露心脏。在切断迷走神经之前、之后以及给予普萘洛尔之后，使用特制装置对窦房结进行牵张。窦房结牵张以以下方式降低心率变异性：逐搏间期的标准差降低（从4.2毫秒降至2.6毫秒；P = 0.004），高频成分减少（对照组为6.5±2.2毫秒²，牵张时为1.4±0.3毫秒²，P = 0.003）。切断双侧迷走神经后，窦房结牵张使高频成分减少（对照组为2.8±0.9毫秒²，牵张时为1.2±0.3毫秒²；P = 0.05）。同样，在切断双侧迷走神经并进行β受体阻滞剂治疗后，窦房结牵张降低了高频成分（对照组为10.6±3.5毫秒²，牵张时为3.0±1.5毫秒²；P = 0.01）。
我们得出结论，窦房结牵张会降低高频心率变异性。这可能部分解释了在右心房扩张的临床情况下，如充血性心力衰竭中观察到的心率变异性降低。
