Hirose Masamichi, Carlson Mark D, Laurita Kenneth R
Heart & Vascular Research Center, Case Western Reserve University, Cleveland, Ohio 44109-1998, USA.
J Cardiovasc Electrophysiol. 2002 Sep;13(9):918-26. doi: 10.1046/j.1540-8167.2002.00918.x.
Increased vagal tone significantly enhances susceptibility to atrial fibrillation (AF); however, the cellular mechanisms responsible for vagally mediated AF are not completely understood.
In 12 isolated arterially perfused canine right atria, high-resolution optical mapping techniques were used to measure action potentials during control conditions, during intracardiac parasympathetic nerve stimulation (IPS; 30 to 50 Hz) as a surrogate for vagal stimulation, and during acetylcholine (ACh) infusion (10 to 30 microM). During steady-state pacing, action potential duration was shorter during ACh infusion (43 +/- 9 msec) than during IPS (78 +/- 7 msec, P < 0.001) or control (129 +/- 5 msec, P < 0.001). In contrast, repolarization gradients were larger during IPS (13 +/- 3 msec/mm) than during ACh infusion (3 +/- 1 msec/mm, P < 0.01) or control (5 +/- 1 msec/mm, P < 0.01). Transmural repolarization gradients were relatively small for each intervention tested. During ACh infusion, atrial tachyarrhythmia (AT) was easily initiated with a single premature stimulus and was associated with a focal pattern of activation (84%). AT also was easily initiated by a single premature stimulus during IPS; however, when repolarization gradients were large, patterns of conduction block and incomplete macroreentry were often observed (64%). Importantly, AT initiation during IPS was associated with focal activity (36%) when repolarization gradients were small.
In contrast to ACh infusion, IPS generally increased dispersion of repolarization and was often associated with patterns of conduction block and incomplete macroreentry, similar to that associated with in vivo cervical vagal stimulation. However, IPS also was associated with a focal pattern of initiation that was independent of local repolarization gradients. These results suggest that during vagal stimulation, AT initiation does not always depend on repolarization gradients.
迷走神经张力增加会显著增强心房颤动（AF）的易感性；然而，迷走神经介导的房颤的细胞机制尚未完全明确。
在12个离体动脉灌注犬右心房中，采用高分辨率光学标测技术，在对照条件下、心内副交感神经刺激（IPS；30至50Hz）作为迷走神经刺激的替代以及乙酰胆碱（ACh）输注（10至30μM）期间测量动作电位。在稳态起搏期间，ACh输注期间的动作电位持续时间（43±9毫秒）短于IPS期间（78±7毫秒，P<0.001）或对照期间（129±5毫秒，P<0.001）。相反，IPS期间的复极梯度（13±3毫秒/毫米）大于ACh输注期间（3±1毫秒/毫米，P<0.01）或对照期间（5±1毫秒/毫米，P<0.01）。每种测试干预的跨壁复极梯度相对较小。在ACh输注期间，单个早搏刺激很容易引发房性快速性心律失常（AT），并且与局灶性激动模式相关（84%）。在IPS期间，单个早搏刺激也很容易引发AT；然而，当复极梯度较大时，经常观察到传导阻滞和不完全大折返模式（64%）。重要的是，当复极梯度较小时，IPS期间的AT起始与局灶性活动相关（36%）。
与ACh输注相反，IPS通常会增加复极离散度，并且经常与传导阻滞和不完全大折返模式相关，类似于体内颈迷走神经刺激相关的模式。然而，IPS也与独立于局部复极梯度的局灶性起始模式相关。这些结果表明，在迷走神经刺激期间，AT起始并不总是依赖于复极梯度。
