Increase of QRS duration as a predictor of impending ventricular fibrillation during coronary artery occlusion

Increased QRS duration (QRSd) has been observed during acute myocardial ischemia and infarction, indicating conduction deterioration in the myocardial tissue. It has been reported that intramyocardial conduction velocity slowing induced by ischemia is associated with the occurrence of malignant ventricular arrhythmias. However, clinically useful QRSd cut-offs that would predict immediate ventricular fibrillation (VF) onset have not been identified. In this work, we studied the association between QRSd prolongation and VF occurrence in a porcine model of myocardial infarction. Infarction was induced in 32 pigs by 40-minute-long balloon inflation in LAD coronary artery under continuous ECG monitoring. After applying a wavelet-based delineator to the ECG precordial leads, QRSd was measured and its local increase in a sliding window of 3 minutes (ΔQRSd) was continuously computed during the occlusion. Choosing a threshold for ΔQRSd = 28ms from a ROC curve analysis, 8 out of 10 VF episodes could be predicted (Se=80%, Sp=90.9%, NPV=90.9%, PPV=80%). Results suggest that a transient increase in QRSd may be a sensitive and specific index for monitoring immediate risk of malignant ventricular arrhythmias during acute myocardial ischemia.