Watanabe Ichiro, Gettes Leonard S
Division of Cardiology, Department of Medicine, Nihon University School of Medicine.
Division of Cardiology, Department of Medicine, University of North Carolina at Chapel Hill.
Int Heart J. 2017 May 31;58(3):428-434. doi: 10.1536/ihj.16-305. Epub 2017 May 8.
Acute myocardial ischemia causes TQ depression and ST elevation. However, the effects of cardioprotective drugs such as β-blockers and Ca-antagonists on the extent of TQ depression, ST elevation, and myocardial ischemic injury are not fully understood.We created a carotid-coronary shunt in 30 pigs, and extracellular K ([K]), TQ, and ST segments were recorded simultaneously with K-selective plunge electrodes placed in the left anterior descending artery (LAD) distribution during graded LAD flow reduction before and after administration of propranolol or verapamil. Unipolar DC-coupled electrograms were recorded from the reference pole of the K-selective plunge electrodes. The microvolt readings from the K-selective electrodes were converted to [K] and then to the changes in potassium equilibrium potential (ΔE). The shunted LAD flow was reduced in a stepwise fashion at 5-minute intervals.segment depression at the similar ΔE was not affected by propranolol or verapamil. However, ST segment elevation was reduced by propranolol but exacerbated by verapamil at the similar ΔE.TQ-ST changes recorded by AC coupled ECG are not a reliable index of ischemia and therefore cannot be used to evaluate the effects of drugs that might affect the electrophysiologic properties of ischemic myocardium.
急性心肌缺血会导致TQ段压低和ST段抬高。然而，β受体阻滞剂和钙拮抗剂等心脏保护药物对TQ段压低程度、ST段抬高程度以及心肌缺血损伤的影响尚未完全明确。我们在30头猪身上建立了颈-冠状动脉分流模型，在给予普萘洛尔或维拉帕米前后，于左前降支（LAD）血流逐渐减少的过程中，使用置于LAD分布区域的钾选择性插入式电极同时记录细胞外钾（[K]）、TQ段和ST段。从钾选择性插入式电极的参考极记录单极直流耦合心电图。钾选择性电极的微伏读数被转换为[K]，然后再转换为钾平衡电位的变化（ΔE）。分流的LAD血流以5分钟的间隔逐步减少。在相似的ΔE时，TQ段压低不受普萘洛尔或维拉帕米的影响。然而，在相似的ΔE时，普萘洛尔可使ST段抬高降低，而维拉帕米则使其加剧。通过交流耦合心电图记录的TQ-ST变化不是可靠的缺血指标，因此不能用于评估可能影响缺血心肌电生理特性的药物的作用。
