心肌梗死后愈合的猫心内膜下浦肯野纤维的自律性、触发活动及对肾上腺素能刺激的反应

Automaticity, triggered activity, and responses to adrenergic stimulation in cat subendocardial Purkinje fibers after healing of myocardial infarction.

作者信息

Kimura S, Bassett A L, Kohya T, Kozlovskis P L, Myerburg R J

出版信息

Circulation. 1987 Mar;75(3):651-60. doi: 10.1161/01.cir.75.3.651.

DOI:10.1161/01.cir.75.3.651

Abstract

We studied automaticity, triggered activity, and responses to alpha- and beta-adrenergic stimulation in subendocardial Purkinje fibers overlying healed infarct scars (infarct preparation) and from remote normal zones (noninfarct preparation) of cat left ventricles. The preparations were studied 2 to 4 months after ligation of multiple distal tributaries of the left anterior descending and circumflex arteries. Subendocardial Purkinje fibers from corresponding areas of normal hearts served as control samples (control preparation). Transmembrane action potential characteristics and rates of automaticity (spontaneous phase 4 depolarization) did not differ among control, noninfarct, and infarct preparations. However, overdrive at cycle lengths of less than 400 msec suppressed automaticity to a greater degree in Purkinje fibers of infarct preparations than those of control and noninfarct preparations. Changes in automatic rate during superfusion with isoproterenol (10(-10)M to 10(-6)M) were not different among the three groups of preparations, but exposure to phenylephrine (10(-9)M to 10(-5)M) in the presence of 5 X 10(-7)M propranolol reduced the automatic rate to a greater degree in Purkinje fibers of infarct preparations than those of control or noninfarct preparations. Triggered activity arising from delayed afterdepolarizations was recorded in 10 of 29 infarct preparations (34%), but not in 12 control and 10 noninfarct preparations. These afterpotentials were augmented by increasing extracellular Ca++ concentration, 10(-7)M isoproterenol, and 10(-5)M phenylephrine in the presence of 5 X 10(-7)M propranolol. We conclude that Purkinje fibers overlying healed infarct scars have altered physiology of spontaneous automaticity, enhanced responses to alpha-adrenergic interventions, and a tendency to triggered activity, and that both alpha- and beta-adrenergic effects may result in worsening of arrhythmias by augmentation of afterpotentials in healed myocardial infarction.

摘要

我们研究了猫左心室愈合梗死瘢痕上方的心内膜下浦肯野纤维（梗死标本）以及来自远端正常区域（非梗死标本）的自动节律性、触发活动以及对α和β肾上腺素能刺激的反应。这些标本是在结扎左前降支和回旋支的多个远端分支后2至4个月进行研究的。来自正常心脏相应区域的心内膜下浦肯野纤维用作对照样本（对照标本）。对照、非梗死和梗死标本的跨膜动作电位特征和自动节律率（自发4期去极化）并无差异。然而，在周期长度小于400毫秒的超速驱动下，梗死标本的浦肯野纤维自动节律性受抑制的程度比对照和非梗死标本的更大。在三组标本中，用异丙肾上腺素（10⁻¹⁰M至10⁻⁶M）灌注期间自动节律率的变化并无不同，但在存在5×10⁻⁷M普萘洛尔的情况下，暴露于去氧肾上腺素（10⁻⁹M至10⁻⁵M）时，梗死标本的浦肯野纤维自动节律率降低的程度比对照或非梗死标本的更大。在29个梗死标本中有10个（34%）记录到了由延迟后去极化引起的触发活动，但在12个对照标本和10个非梗死标本中未记录到。在存在5×10⁻⁷M普萘洛尔的情况下，增加细胞外Ca²⁺浓度、10⁻⁷M异丙肾上腺素和10⁻⁵M去氧肾上腺素可增强这些后电位。我们得出结论，愈合梗死瘢痕上方的浦肯野纤维具有改变的自发自动节律生理学、对α肾上腺素能干预的增强反应以及触发活动的倾向，并且α和β肾上腺素能效应均可能通过增强愈合心肌梗死中的后电位而导致心律失常恶化。