Ventricular activation in normal sinus rhythm: abnormalities with recurrent sustained tachycardia and a history of myocardial infarction.

Left ventricular activation was studied in 21 patients: 7 with normal electrocardiograms (group I), 7 with prior transmural myocardial infarction (group II) and 7 with prior transmural myocardial infarction (MI) and recurrent sustained ventricular tachycardia (VT) (group III). Fragmented electrograms were defined as those less than 3 mV in amplitude and longer than 60 ms in duration. Such electrograms were found in no group I patients, 6 of 7 group II patients and all 7 group III patients. An average of 2 of the 12 sites mapped in each patient displayed fragmented electrograms in group II; an average of 6 of the 12 sites displayed fragmented electrograms in group III (p less than 0.01). Twelve of the 84 total sites mapped in group II displayed fragmented electrograms, whereas 39 of the 84 sites mapped in group III patients did (p less than 0.01). The longest fragmented electrogram found in the 6 group II patients in whom such electrograms were found was shorter in duration than the longest electrogram found in each of the 7 group III patients with fragmented electrograms (76 ms vs 135 ms, p less than 0.005). The duration of endocardial activation was longer in group II patients (79 +/- 7 ms) than in group I patients (39 +/- 4 ms, p less than 0.001). Duration of activation was also longer in group III patients (151 +/- 12 ms) than in either of the other groups (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)