Ischemia modulation via coronary revascularization and effects on the arrhythmic substrate

BackgroundBoth ischemia and scar can contribute to arrhythmogenesis in patients with ischemic left ventricular dysfunction (ILVD); coronary revascularization is frequently undertaken to modify the former. Whether modulation of ischemia affects the substrate for ventricular arrhythmia is unclear. ObjectivesTo assess the mechanistic effects of ischemia modulation via revascularization on the arrhythmic substrate in patients with ILVD. MethodsPatients were eligible for enrolment if they had a left ventricular ejection fraction (LVEF)[&le;]40%, extensive coronary disease (BCIS jeopardy score >6/12) and were scheduled to undergo percutaneous coronary intervention (PCI) or coronary artery bypass surgery (CABG). Scar and ischemic burden were assessed via stress-perfusion cardiac magnetic resonance (pCMR), calculated as a percentage of total LV myocardial volume. Arrhythmic substrate was characterised by non-invasive electrocardiographic imaging (ECGi). ECGi and pCMR were repeated 3 months after revascularization. The primary outcome was change in the LV activation recovery interval (ARI) dispersion. ResultsThirty patients were enrolled (age 67{+/-}10 years, 87% male, LVEF 29{+/-}7%); 12 (40%) underwent CABG, 18 (60%) had PCI. Following revascularization, LVEF increased (+8{+/-}8%) and ischemic burden reduced (-34{+/-}24%)(p<0.01). There was no change in mean LV ARI dispersion, however individual changes in LV ARI dispersion correlated with individual changes in ischemic burden (r=0.51,p<0.01). Baseline LV volumes, scar burden, delta LVESVi and delta ischemia were all predictors of improvement. ConclusionsArrhythmic substrate was correlated with scar burden and was not altered by revascularization. Revascularization may not routinely reduce arrhythmic risk. Further work is needed to prospectively identify select patients who may confer benefit.