Effect of Acute Myocardial Ischemia on Inferolateral Early Repolarization.

BACKGROUND

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

OBJECTIVE

To determine the effect of myocardial ischemia on ER.

METHODS

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

RESULTS

Seventy-seven patients with ER in the pre-procedural 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 (44%) cases from 0.00±0.03 mV to 0.05±0.06 mV (p<0.0001). In this group, J-wave amplitude (JWA) increased from 0.10±0.07 mV to 0.13±0.09 mV (p<0.0001). ST in the ER lead decreased or was unchanged in 121 cases (56%) from PRE to OCCL (0.01±0.05 mV to -0.02±0.04 mV; p<0.0001). In this group, JWA decreased from 0.10±0.05 to 0.08±0.07 mV (p<0.0001). The change in JWA was related to the change in ST (linear regression analysis; R squared=0.34; p<0.0001), while there was no relation between change in R-wave amplitude and change in ST (R squared=0.0003, p=0.83).

CONCLUSIONS

During acute ischemia, J-wave amplitude 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.