Michiyo Hosokawa

Epicardial mapping during induction of nonsustained polymorphic ventricular tachycardia in a 7-day-old canine myocardial infarction model

Programmed electrical stimulation and epicardial mapping were performed to study electrophysiologic mechanisms for induction of nonsustained polymorphic ventricular tachycardia in 29 dogs with 7-day-old myocardial infarction. Nine dogs had 15 different episodes of reproducible monomorphic ventricular tachycardia (11 sustained and 4 nonsustained) (group A). Seven episodes of polymorphic ventricular tachycardia (group B) were induced in six dogs, three of which degenerated into ventricular fibrillation. Epicardial activation time during premature stimulation at the time of tachycardia induction was more prolonged in group A than in group B (183 +/- 43 vs 123 +/- 35 msec, p less than 0.01). Furthermore, induction of ventricular tachycardia was preceded by the development of functional block in 13 of 15 group A tachycardias, but in only three of seven group B tachycardias. During polymorphic ventricular tachycardia, epicardial activation patterns were radial from the earliest epicardial activation site, similar to those observed during left ventricular endocardial pacing. QRS polymorphism was associated with a beat-to-beat variation in the earliest epicardial activation site. In conclusion, inducibility of nonsustained polymorphic ventricular tachycardia is less dependent on the epicardial activation sequence than on monomorphic ventricular tachycardia.

Rapid Growth of Left Ventricular Thrombus Leading to Fatal Heart Failure in Six Hours

A left ventricular (LV) thrombus grew rapidly over chronic endocarditis 2 months after anterior myocardial infarction. Echocardiograms demonstrated a rapidly growing LV thrombus an eventual obstruction. Despite anticoagulant/thrombolytic therapy, the patient died of acute LV failure. Histopathologically, a fresh thrombus overlay thickened endocardium with massive T lymphocyte infiltration over healed infarction.