196 A Significant Proportion of Post-infarct VT is Unrelated to Acute Myocardial Scar

Abstract

Ventricular tachycardia (VT) is a leading cause of sudden cardiac death post ST elevation myocardial infarction (STEMI). Guidelines dictate evaluating ejection fraction 40 days post coronary re-vascularisation for risk stratification. VT in chronic ischaemic cardiomyopathy is almost exclusively from myocardial scar related re-entry, however VT immediately post STEMI is not as well understood. We retrospectively studied 46 patients who presented to Westmead Hospital with STEMI (2014-2019), a left ventricular ejection fraction (LVEF) <40%, and inducible VT on electrophysiology study (EPS). 12-lead ECGs of the induced VTs were comprehensively analysed and compared to scar location determined by regional wall abnormality on gated heart pool scan (GHPS). These were plotted on a 17-segment model of the LV. The study included 46 patients (male =37, female =9) with an average age 60.6 (33-80). The mean time from STEMI to EPS was 12.0 days (4-36), and average LVEF was 30.2%. The average VT cycle length and extra stimuli required were 221.8 and 3.2 respectively. Of the 50 VTs analysed, 18 (36%) did not match the GHPS determined scar site. Of these, 7 (39%) were within 1 segment of scar-border, 2 (11%) were within 2 segments. 9 (50%) were deemed completely remote. 32 (64%) VTs arose from within the scar-border. Whilst acute ischaemic scar related re-entry may still explain the majority of inducible VT post STEMI, a significant proportion may be due to remote automaticity, which may be a target for acute catheter ablation.