Ventricular ectopic beats induced in the ischemic zone caused ventricular tachycardia significantly earlier (mean 3 min, 22 sec) than those in the normal zone (mean 4 min, 11 sec; P<0.01).
Does the induction of ventricular ectopic beats in the ischemic zone compared to the normal zone accelerate the onset of ventricular tachycardia during acute myocardial ischemia?
In an acute ischemia dog model, abnormalities of ventricular activation rather than the coupling of premature ectopic beats are the major determinant of malignant ventricular arrhythmias.
p-value: p=<0.01
In 20 anesthetized open-chest dogs, epicardial electrograms were recorded from ischemic and nonischemic zones of the left ventricle during acute occlusion of the left anterior descending artery. The average time to onset of ventricular tachycardia during atrial pacing (150-200 beats/min) was 4 min, 18 sec. In 18 dogs, ventricular ectopic beats were induced in normal and ischemic zones after every tenth atrial stimulus. Those induced in the ischemic zone consistently caused ventricular tachycardia earlier (mean: 3 min, 22 sec) than those in the normal zone (mean: 4 min, 11 sec) ( P < 0.01). This arrhythmia, whether spontaneous or induced, always followed the complex which demonstrated the greatest delay of the ischemic zone potential and increased ventricular activation time. Ventricular tachycardia was repeatedly produced by ectopic beats with late diastolic coupling. Analysis of the episodes of tachycardia leading to fibrillation revealed a progressive increase in the ventricular activation time of the successive beats, whereas in those self-terminating episodes ventricular activation time progressively decreased. These data suggest that the major determinant of malignant ventricular arrhythmias in acute ischemia may be the related abnormalities of ventricular activation rather than the coupling of the premature ectopic beats.
Williams et al. (Sun,) conducted a other in Acute Myocardial Ischemia (n=20). Ventricular ectopic beats induced in ischemic zone vs. Ventricular ectopic beats induced in normal zone was evaluated on Time to onset of ventricular tachycardia (p=<0.01). Ventricular ectopic beats induced in the ischemic zone caused ventricular tachycardia significantly earlier (mean 3 min, 22 sec) than those in the normal zone (mean 4 min, 11 sec; P<0.01).