Initiation patterns of monomorphic ventricular tachycardia in acute myocardial infarction: analysis of rhythm strips

Objective - Monomorphic ventricular tachycardias (MVT) frequently occur in the acute phase of myocardial infarction (MI). In the past, some studies aimed to investigate the initiation pattern of ventricular tachycardias, although not in acute MI patients. The aim of the present study was to analyse the initiation pattern of MVT in acute MI using rhythm strips. Methods - This study utilized data on 255 rhythm strips defined as MVT, from 173 patients with acute ST-segment elevation MI. Monomorphic ventricular tachycardias that were not preceded by ventricular ectopic beats were defined as sudden onset MVT. Monomorphic ventricular tachycardias which were preceded by a single or multiple ectopic beats, including a short-long-short sequence, were defined as non-sudden onset MVT. Results - Non-sudden onset episodes were more common than sudden onset episodes (172 episodes, 67.4% versus 83 episodes, 32.5%). The morphology of the ventricular ectopic beat initiating tachycardia was similar to the first beat of MVT in 127 episodes (73.8%), but not in the remaining 45 episodes (26.1%). In the non-sudden onset group, 117 episodes (68%) initiated with a single ectopic beat, while 55 episodes (32%) initiated with multiple complexes. The left ventricular ejection fraction of the patients with non-sudden onset MVT was lower (50 6 versus 56 5, P < 0.05). Monomorphic ventricular tachycardias with no sudden onset also had shorter coupling intervals (CI) (P < 0.001) and shorter prematurity index (PI) (P < 0.001) than MVT with sudden onset. Similarly, the ventricular tachycardia cycle length was shorter in the group of MVT subjects with non-sudden onset as compared with sudden onset (P < 0.05). In contrast, tachycardias with sudden onset were associated with a shorter preceding RR interval (P < 0.01). Conclusions - Analysis of rhythm strips demonstrated that MVT is most often preceded by ventricular ectopic beats in the acute phase of MI.