PROFIBRILLATORY EFFECTS OF INTRACORONARY THROMBUS IN ACUTE REGIONAL ISCHEMIA OF THE IN-SITU PORCINE HEART

Background An intracoronary thrombus during regional ischemia is relat ed to life-threatening arrhythmias. The electrophysiological consequen ces of a thrombus are unknown. Methods and Results In open chest pigs, regional ischemia was induced by intracoronary injection of a thrombu s (protocol 1). In protocol 2, coronary ligation was followed by injec tion 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 recor ded simultaneously, and activation patterns were determined. In a firs t period of ischemia, ventricular fibrillation (during the first 10 mi nutes) occurred more often after intracoronary thrombosis than during the other protocols (4/7 Versus 2/19, P<.05) despite similar size of t he ischemic tissue. The incidence of delayed arrhythmias (between 15 a nd 30 minutes) was not different. Epicardial activation delay was larg er 2 to 4 minutes after intracoronary thrombosis compared with ligatio n. 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 ir respective of the presence of an intracoronary thrombus. Conclusions M ore conduction slowing underlies the profibrillatory effect of an intr acoronary thrombus relative to coronary ligation. After preconditionin g with ischemia, the profibrillatory effects are no longer detectable.