ROLE OF THE PURKINJE SYSTEM IN SPONTANEOUS VENTRICULAR-TACHYCARDIA DURING ACUTE-ISCHEMIA IN A CANINE MODEL

Background A role for the Purkinje system in the development of sponta neous ventricular tachycardia (VT) during acute ischemia has been susp ected but not proved. We used a three-dimensional activation mapping s ystem incorporating Purkinje signals to characterize the mechanism and site of origin of spontaneous VT occurring in the first 30 minutes af ter coronary artery occlusion in a dog model. Methods and Results The left anterior descending coronary artery was occluded in 48 dogs after instrumentation of the risk zone with 21 multipolar plunge needles, e ach recording 6 bipolar electrograms through the myocardial wall. VT o f Purkinje origin was defined as a focal endocardial VT with a Purkinj e potential identified before muscle potential on the electrode record ing the earliest activity. Purkinje potentials were identified on an a verage of 10 of the 21 plunge needles, During atrial pacing at cycle l engths of 300 to 700 ms, a total of 25 VTs were observed from 18 of th e 48 dogs (37.5%). Of the VTs, 15 (60.0%) were of focal Purkinje origi n, 1 (4.0%) of focal endocardial origin, 2 (8.0%) of focal midmyocardi al origin, and 2 (8.0%) of focal epicardial origin; 3 (12.0%) had a re entrant mechanism, whereas in 2 (8.0%), the mechanism could not be def ined. The mean cycle length of all VTs was 265 +/- 17 ms (mean +/- SEM , n = 25). Of the 25 VTs, 19 originated from an ischemic area as defin ed by significant decreases in voltages of muscle electrograms at the time of occurrence of the VT, 4 originated from an ischemic border zon e, and the origin of 2 could not be determined. Conclusions In this mo del, VT with a focal mechanism is commonly seen in the early ischemic period. Sixty percent of the VTs were of focal Purkinje origin as char acterized by three-dimensional activation mapping. The results of this study indicate that Purkinje tissue may play an important role in the development of early ischemic VT.