Experimental myocardial infarction in a canine model resulted in time-dependent changes in VT/VF inducibility, with MI mass being the only independent predictor after day 15 (p=0.049).
Does the inducibility of ventricular arrhythmias change over time in a canine model of myocardial infarction?
In a canine myocardial infarction model, the inducibility of ventricular arrhythmias varies significantly in the early phase but stabilizes after day 15, with infarct mass being the primary predictor of inducibility.
To study the time course of spontaneous and induced ventricular arrhythmias after myocardial infarction (MI), 20 dogs underwent ligation of the left anterior descending coronary artery and temporary occlusion and reperfusion of the obtuse marginal branch. There were 5 early deaths (less than 24 hours) due to spontaneous ventricular fibrillation (VF). All 15 survivors exhibited spontaneous ventricular tachycardia (VT) up to day 3 with the shortest cycle length occurring at 17 hours after MI (232 +/- 11 msec: mean +/- SEM). The grade of arrhythmia complexity was decreased after day 4 compared to day 1 (p = 0.049), and the number of ventricular premature complexes was reduced after day 6 (1700 +/- 1390/hour) compared to day 1 (9500 +/- 640/hour, p = 0.042). Serial electrophysiologic studies were carried out on days 8, 15, 22, and 29 via an implanted antitachycardia pacemaker using 1 to 3 extrastimuli and rapid ventricular pacing (RVP). On day 8, VT was inducible in 7 dogs (46%), VF in 4 (27%), and 4 dogs (27%) exhibited a negative response. On day 15, 3 more dogs became negative, and all previously negative dogs displayed negative responses. From day 15, the inducibility of VT/VF remained "constant" using RVP. However, inducibility by triple extrastimuli declined week by week until day 29. Stepwise logistic regression analysis of 20 variables selected the mass of the MI as the only independent predictor of inducible VT/VF by multiple extrastimuli and RVP after day 15 (p = 0.049). Thus significant time- and mode-dependent changes in inducibility of VT/VF occur during the early phase after MI.
Nogami et al. (1988) studied Myocardial infarction and ventricular arrhythmias (n=20). Experimental myocardial infarction and serial electrophysiologic studies was evaluated on Time course of spontaneous and induced ventricular arrhythmias. Experimental myocardial infarction in a canine model resulted in time-dependent changes in VT/VF inducibility, with MI mass being the only independent predictor after day 15 (p=0.049).