Perimitral ventricular tachycardia associated with remote inferior myocardial infarction

INTRODUCTION: Circuits underlying ventricular tachycardias (VTs) accompanying remote inferior myocardial infarction (IMI) are regarded to be located in the scar. Rotation around the mitral annulus (MA) had also been postulated. We tested whether entrainment mapping could confirm whether MA rotation in VTs post-IMI represented a "driving circuit." METHODS: Three patients with IMI (male, left ventricular ejection fraction range 13%-40%) with hemodynamically tolerated VT (cycle length 365-690 ms) were studied with activation and entrainment mapping of the MA. RESULTS: Patients showed QRS morphologies reported for VTs following IMI: LBBB (left bundle branch block) pattern and/or right bundle pattern. Entrainment revealed the entire MA perimeter constituted the circuit, that is, macroreentry (path length greater than 13 cm in one case). Areas showing prolonged fractionated electrograms (accounting for over 50% of tachycardia cycle length) demonstrated concealed entrainment indicative of slow conduction through (and not around) the scar. Concealed entrainment was observed along the MA, with similar stimulus-QRS intervals when pacing during normal sinus rhythm. Radiofrequency ablation of the inferior isthmus from scar to MA (epicardially in one case) abolished tachycardia. In follow-up, two patients had no VT recurrence and maintained NYHA Class 1 functional status during several years of follow-up. The other patient continued to deteriorate with rapidly progressive HF, had recurrent VT within 3 months, proceeding to transplant within 9 months. Our findings confirm a single-loop perimitral circuit, which is largely (if not exclusively) protected by anatomical barriers. This differs from the established "figure-of-8" VT model. CONCLUSION: Single-loop macroreentrant mitral annular circuits may underlie some VTs following inferior wall infarcts.