Online supplement to "Regional beat-to-beat variability of repolarization increases during ischemia and predicts imminent arrhythmias in a pig model of myocardial infarction"

Online supplement to "Regional beat-to-beat variability of repolarization increases during ischemia and predicts imminent arrhythmias in a pig model of myocardial infarction" submitted to American Journal of Physiology-Heart and Circulatory Physiology.

Abstract
Background
Ventricular arrhythmia (VT/VF) can complicate acute myocardial ischemia (AMI). Regional instability of repolarization during AMI contributes to the substrate for VT/VF. Beat-to-beat variability of repolarization (BVR), a measure of repolarization lability increases during AMI. We hypothesized that its surge precedes VT/VF. We studied the spatial and temporal changes in BVR in relation to VT/VF during AMI.
Methods
In 24 pigs BVR was quantified on 12-lead electrocardiogram (ECG) recorded at a sampling rate of 1kHz. AMI was induced in 16 pigs by percutaneous coronary artery occlusion (MI), while 8 underwent sham-operation (Sham). Changes in BVR were assessed at 5-minutes after occlusion, 5- and 1-minute pre-VF in animals that developed VF and matched time points in pigs without VF. Serum troponin and ST deviation were measured. After 1-month, magnetic resonance imaging and VT induction by programmed electrical stimulation were performed.
Results
During AMI, BVR increased significantly in inferior-lateral leads correlating with ST-deviation and troponin increase. BVR was maximal 1-minute pre-VF (3.78±1.36 vs 5-minutes pre-VF: 1.67±1.56, P < 0.0001). After 1-month, BVR was higher in MI than sham and correlated with the infarct size (1.43±0.50, vs 0.57±0.30, P = 0.009). VT was inducible in all MI animals and the ease-of-induction correlated with BVR.
Conclusion
BVR increased during AMI and temporal BVR changes predicted imminent VT/VF supporting a possible role in monitoring and early-warning systems. BVR correlated to arrhythmia vulnerability suggesting utility in risk stratification post-AMI.

This supplement contains additional analysis and figures not included in the original publication.