ARRHYTHMOGENIC INFLUENCE OF INTRACORONARY THROMBOSIS DURING ACUTE MYOCARDIAL-ISCHEMIA

Background Patients with acute coronary artery thrombosis often develo p primary malignant ventricular arrhythmias (MVA) early after coronary occlusion. In contrast, acute ischemia induced by nonthrombotic ballo on occlusion during routine coronary angioplasty rarely elicits such a rrhythmias. This study was designed to assess the role of intracoronar y thrombosis in arrhythmogenesis during acute ischemia. Methods and Re sults We compared the incidence of MVA associated with acute left ante rior descending coronary artery (LAD) thrombosis elicited in open-ches t anesthetized dogs by electrical injury (n=10) or intracoronary stent (n=9) versus LAD balloon occlusion (n=15). Compared with animals subj ected to balloon occlusion, those with thrombotic occlusion had a sign ificantly greater incidence of MVA, defined as nonsustained ventricula r tachycardia (total duration >10 seconds), sustained ventricular tach ycardia, or ventricular fibrillation developing within the first 30 mi nutes of occlusion. In the combined thrombosis groups, MVA developed i n 11 of 19 animals (58%) (6 of 10 dogs with electrical injury and 5 of 9 stent animals). In contrast, MVA occurred in only 1 of 15 animals ( 7%) subjected to balloon occlusion. This striking and significant diff erence in arrhythmias occurred despite the fact that radioactive micro sphere perfusion analysis documented that the extent of left ventricul ar myocardium rendered ischemic was equal in all groups (percent of le ft ventricular myocardium with occlusion flow less than or equal to 50 % of baseline: electrical injury, 25.2+/-5.3%; stent, 27.1+/-3.6%; bal loon, 34.3+/-11.6%; P=NS). Furthermore, there were no differences betw een the animals with thrombosis or balloon occlusion with respect to c hanges in echocardiographic parameters of left ventricular function, a ortic pressure, or heart rate after occlusion. Conclusions These data provide evidence that despite equal magnitudes of jeopardized myocardi al mass, acute ischemia induced by thrombotic coronary occlusion resul ts in a greater incidence of MVA than does nonthrombotic balloon occlu sion. These findings suggest that the process of intracoronary thrombo sis itself exerts arrhythmogenic effects above and beyond the impact o f ischemia on myocardium induced by coronary occlusion.