Optimization of the global re-entry vulnerability index to minimise cycle length dependency and prediction of ventricular arrhythmias during human epicardial sock mapping

The re-entry vulnerability index (RVI) is an activation-repolarization marker recently proposed to predict sites of ventricular tachycardia (VT) initiation. RVI is inversely related to the probability of establishing a re-entry. The aim of this study was to characterize the CL dependency of RVI, assess different methods for CL-dependency corrections and test the capability of RVI to predict ventricular arrhythmias. Twenty-four subjects underwent whole heart epicardial mapping using a multi-electrode sock enabling the recording of 240 unipolar electrograms. Ventricular pacing was delivered at CLs decreasing from 600 to 350 ms in steps of 50 ms. In a separate study, 1 patient went into VT during steady state pacing. Predisposition to VTwas assessed by using the 10th percentile RVI, termed global RVI. The results show that own to CL dependency of local repolarization, there was a strong positive association between RVI and CL. Local repolarization detrending and correction with the Bazett's formula eliminated the CL dependency, while a weak association was found after correction with the Fredericia's formula. In the patient who developed VT, global RVI was significantly lower than in the patients who did not develop VT. Corrections for CL dependency enhanced these differences. In conclusion, de-trending and Bazett's corrections effectively compensated for the CL dependency of RVI and global RVI may reveal predisposition to ventricular arrhythmias. Further analysis is necessary to establish the role of RVI for risk stratification.