Abstract
BackgroundThe re-entry vulnerability index (RVI) is a recently proposed activation-repolarization metric designed to quantify tissue susceptibility to re-entry. This study aimed to test feasibility of an RVI-based algorithm to predict the earliest endocardial activation site of ventricular tachycardia (VT) during electrophysiological studies and occurrence of haemodynamically significant ventricular arrhythmias in follow-up. MethodsPatients with Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) (n = 11), Brugada Syndrome (BrS) (n = 13) and focal RV outflow tract VT (n = 9) underwent programmed stimulation with unipolar electrograms recorded from a non-contact array in the RV. ResultsLowest values of RVI co-localised with VT earliest activation site in ARVC/BrS but not in focal VT. The distance between region of lowest RVI and site of VT earliest site (Dmin) was lower in ARVC/BrS than in focal VT (6.8 ± 6.7 mm vs 26.9 ± 13.3 mm, p = 0.005). ARVC/BrS patients with inducible VT had lower Global-RVI (RVIG) than those who were non-inducible (−54.9 ± 13.0 ms vs −35.9 ± 8.6 ms, p = 0.005) or those with focal VT (−30.6 ± 11.5 ms, p = 0.001). Patients were followed up for 112 ± 19 months. Those with clinical VT events had lower Global-RVI than both ARVC and BrS patients without VT (−54.5 ± 13.5 ms vs −36.2 ± 8.8 ms, p = 0.007) and focal VT patients (−30.6 ± 11.5 ms, p = 0.002). ConclusionsRVI reliably identifies the earliest RV endocardial activation site of VT in BrS and ARVC but not focal ventricular arrhythmias and predicts the incidence of haemodynamically significant arrhythmias. Therefore, RVI may be of value in predicting VT exit sites and hence targeting of re-entrant arrhythmias.
Highlights
A significant challenge remains in the prediction of ventricular tachycardia (VT) circuits, especially in disorders of diffuse fibrosis or where the functional characteristics of the substrate play a critical role in the initiation of re-entry
A novel spatial metric has been developed termed the Re-entry Vulnerability Index (RVI), used to locate regions of tissue susceptible to re-entry and VT initiation [1,2] (Fig. 1). This metric can theoretically be applied to predict the initiation site of monomorphic VT, as seen more commonly in Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC), and polymorphic VT seen in Brugada Syndrome (BrS), as both initiate in the same manner around lines of block [3,4,5]
The results of this study provide further evidence that re-entry vulnerability index (RVI) localizes regions of high susceptibility to conduction block and re-entry, with lowest RVI values identifying the earliest endocardial activation site of re-entrant VT but not the origin of focal arrhythmias
Summary
A significant challenge remains in the prediction of ventricular tachycardia (VT) circuits, especially in disorders of diffuse fibrosis or where the functional characteristics of the substrate play a critical role in the initiation of re-entry. A novel spatial metric has been developed termed the Re-entry Vulnerability Index (RVI), used to locate regions of tissue susceptible to re-entry and VT initiation [1,2] (Fig. 1) This metric can theoretically be applied to predict the initiation site of monomorphic VT, as seen more commonly in Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC), and polymorphic VT seen in Brugada Syndrome (BrS), as both initiate in the same manner around lines of block [3,4,5]. Conclusions: RVI reliably identifies the earliest RV endocardial activation site of VT in BrS and ARVC but not focal ventricular arrhythmias and predicts the incidence of haemodynamically significant arrhythmias. RVI may be of value in predicting VT exit sites and targeting of re-entrant arrhythmias
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