Abstract 15418: An Arrhythmogenic Isolated Septal Aneurysm

Abstract

Background: Septal infarct due to isolated occlusion of a perforator branch is extremely rare. Few reported cases only describe either the EKG findings, imaging abnormalities or revascularization techniques. Objective: We report a case of an isolated septal aneurysm (ISA) caused by the acute occlusion of the second septal perforator presenting with recurrent ventricular fibrillation (VF). Results: A 63 year old woman presented to the hospital with chest pain. EKG showed an ST segment elevation localized to lead V3 (Fig1A), troponin 18.23. Angiogram showed an isolated 95% tubular stenosis of large second septal branch of LAD (Fig1B). No revascularization was performed. The patient subsequently had cardiac arrest (VF) requiring cardioversion. Repeat angiogram was unchanged. Echo showed isolated mid septal dyskinetic segment (Fig1C). LVEF was 60%. The patient was discharged with an external defibrillator. Repeat echo showed unchanged EF but presence of the isolated dyskinetic segment. An electrophysiologic study (EPS) showed VF induced with 2 extra stimuli at 250 ms with a drive cycle of 600 ms (Fig1D). An ICD was implanted for prevention of SCD. Conclusion: We describe the first case of an arrhythmogenic ISA in the presence of normal LVEF. The interventricular septum is composed of right and left ventricular endocardium. Experiments have shown that acute septal ischemia produces trans-septal asymmetry in expression of membrane ion channels and action potentials in local conduction velocity and gradients. This results in trans-mural heterogeneity of tissue excitability, a substrate for transmural re-entry and ventricular tachyarrhythmias, in septal infarction. This also explains the persistence of enhanced arrhythmogenicity in our patient during the initial and chronic phases of ischemia. ISA is rare but potentially arrhythmogenic. ISA with preserved LVEF, EPS for arrhythmogenicity and ICD for secondary prevention of SCD should be considered in such cases.