MacConaill M
Department of Pharmacology, University of Ottawa, Ontario.
Can J Cardiol. 1988 Jan-Feb;4(1):49-55.
Consistent threshold concentrations were determined for the precipitation of spontaneous ventricular fibrillation in isolated rabbit hearts by reduction of potassium or increase of calcium in the perfusion solution. The low potassium threshold was a function of the calcium concentration: it increased from 0.81 +/- 0.14 mM (mean +/- SD) with 1.0 mM calcium to 1.58 +/- 0.17 mM with 5.0 mM calcium. The high calcium threshold was 12.8 +/- 2.1 mM at 5.6 mM potassium. Consistent thresholds could not be established when the calcium concentration was greater than 5 mM and potassium concentration less than 3.6 mM. The absolute low potassium and high calcium thresholds did not depend on the potassium and calcium concentrations of the control perfusion solution, being the same whether these were "conventional" (5.6 and 2.25 mM, respectively) or "physiological" (3.6 and 1.6 mM). Spontaneous fibrillation appeared sooner when precipitated by high calcium than when precipitated by low potassium. Many other arrhythmias were observed; these were neither sufficient nor even necessary precursors of spontaneous fibrillation. Particularly with high calcium, spontaneous fibrillation could be the first arrhythmia to appear. Hearts perfused with hypertonic McEwen's solution were more susceptible to the precipitation of fibrillation by low potassium than those perfused with more physiologically balanced solutions. Enhanced susceptibility to precipitation of fibrillation by high calcium concentration was not seen.
通过降低灌注液中的钾离子浓度或增加钙离子浓度，确定了在离体兔心脏中诱发自发性心室颤动的一致阈值浓度。低钾阈值是钙离子浓度的函数：随着钙离子浓度从1.0 mM时的0.81±0.14 mM（平均值±标准差）增加到5.0 mM时的1.58±0.17 mM，低钾阈值也随之升高。在钾离子浓度为5.6 mM时，高钙阈值为12.8±2.1 mM。当钙离子浓度大于5 mM且钾离子浓度小于3.6 mM时，无法确定一致的阈值。低钾和高钙的绝对阈值并不取决于对照灌注液中的钾离子和钙离子浓度，无论对照灌注液是“传统的”（分别为5.6 mM和2.25 mM）还是“生理的”（3.6 mM和1.6 mM），阈值都是相同的。高钙诱发的自发性颤动比低钾诱发的出现得更早。还观察到许多其他心律失常；这些既不是自发性颤动的充分前兆，甚至也不是必要前兆。特别是在高钙情况下，自发性颤动可能是首先出现的心律失常。与灌注更生理平衡溶液的心脏相比，灌注高渗麦克尤恩溶液的心脏对低钾诱发颤动更敏感。未观察到高钙浓度增强颤动诱发易感性的情况。
