Profibrillatory Effects of Intracoronary Thrombus in Acute Regional Ischemia of the In Situ Porcine Heart

Abstract

Background An intracoronary thrombus during regional ischemia is related to life-threatening arrhythmias. The electrophysiological consequences of a thrombus are unknown. Methods and Results In open chest pigs, regional ischemia was induced by intracoronary injection of a thrombus (protocol 1). In protocol 2, coronary ligation was followed by injection of heparinized blood. Three consecutive episodes of ischemia (10 minutes) and reperfusion (20 minutes) were studied in protocols 3 and 4 (ligation). During the former, an intracoronary thrombus started the third period of ischemia. Multiple (78) local electrograms were recorded simultaneously, and activation patterns were determined. In a first period of ischemia, ventricular fibrillation (during the first 10 minutes) occurred more often after intracoronary thrombosis than during the other protocols (4/7 versus 2/19, P <.05) despite similar size of the ischemic tissue. The incidence of delayed arrhythmias (between 15 and 30 minutes) was not different. Epicardial activation delay was larger 2 to 4 minutes after intracoronary thrombosis compared with ligation. ST elevation was larger with than without a thrombus (2 minutes of ischemia, 12.9±4.1 versus 8.2±3.0 mV; ±SD, P <.05). In protocols 3 and 4 the second period and third period of ischemia were similar irrespective of the presence of an intracoronary thrombus. Conclusions More conduction slowing underlies the profibrillatory effect of an intracoronary thrombus relative to coronary ligation. After preconditioning with ischemia, the profibrillatory effects are no longer detectable.