Effect of acute myocardial ischemia on inferolateral early repolarization

Abstract

Background: Inferolateral early repolarization (ER) is associated with an increase in arrhythmic risk, particularly in the presence of myocardial ischemia.

Objective: The purpose of this study was to determine the effect of myocardial ischemia on ER.

Methods: We retrospectively analyzed procedural electrocardiograms (ECGs) of patients with ER undergoing a controlled, 1-minute coronary balloon occlusion for collateral function testing. ECG leads with ER were analyzed immediately before coronary balloon occlusion (PRE), at 60 seconds of coronary balloon occlusion (OCCL), and >30 seconds after balloon deflation.

Results: Seventy-seven patients with ER in the preprocedural ECG (86% inferior, 20% lateral) underwent 135 coronary balloon occlusions during which a J wave was recorded in 224 leads (ER leads). From PRE to OCCL, ST-segment amplitude (ST) in the ER lead increased in 94 cases (44%) from 0.00 ± 0.03 to 0.05 ± 0.06 mV (P < .0001). In this group, J-wave amplitude (JWA) increased from 0.10 ± 0.07 to 0.13 ± 0.09 mV (P < .0001). ST in the ER lead decreased or was unchanged in 121 cases (56%) from PRE to OCCL (from 0.01 ± 0.05 to -0.02 ± 0.04 mV; P < .0001). In this group, JWA decreased from 0.10 ± 0.05 to 0.08 ± 0.07 mV (P < .0001). The change in JWA was related to the change in ST (linear regression analysis; R² = 0.34; P < .0001), while there was no relation between the change in R-wave amplitude and the change in ST (R² = 0.0003; P = .83).

Conclusion: During acute ischemia, JWA mirrors ST-segment changes. This may explain increased arrhythmic vulnerability of patients with ER during myocardial ischemia. It also adds weight to the hypothesis of ER being a phenomenon of repolarization.

Keywords: Early repolarization; Electrocardiography; J wave; Myocardial ischemia; ST-segment elevation.