Assessment of a conduction-repolarisation metric to predict Arrhythmogenesis in right ventricular disorders.

BACKGROUND: The 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. METHODS: Patients 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. RESULTS: Lowest 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 ±â€¯6.7 mm vs 26.9 ±â€¯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 ±â€¯13.0 ms vs -35.9 ±â€¯8.6 ms, p = 0.005) or those with focal VT (-30.6 ±â€¯11.5 ms, p = 0.001). Patients were followed up for 112 ±â€¯19 months. Those with clinical VT events had lower Global-RVI than both ARVC and BrS patients without VT (-54.5 ±â€¯13.5 ms vs -36.2 ±â€¯8.8 ms, p = 0.007) and focal VT patients (-30.6 ±â€¯11.5 ms, p = 0.002). 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. Therefore, RVI may be of value in predicting VT exit sites and hence targeting of re-entrant arrhythmias.

Brugada syndrome: Controversies in Risk stratification and Management.

In the 18 years since the first description of Brugada Syndrome in a small series of cardiac arrest survivors it has become evident that there is a marked spectrum in phenotype and prognosis. An internal cardiac defibrillator (ICD) is the only established therapy but is associated with significant morbidity. A number of registries have published their data, but risk stratification, particularly in asymptomatic patients, remains controversial. This article summarises the evidence to enable the clinician to make informed management decisions on an individual basis.

A review of the mechanisms of ventricular arrhythmia in brugada syndrome.

Brugada syndrome (BrS) is characterised by the triad of coved ST elevation, lethal ventricular arrhythmia in an apparently structurally normal heart. The precise mechanisms responsible for the coved ST elevation and ventricular arrhythmias in this disease have been debated since its initial description in 1992. Indeed the recent recognition of early repolarisation J wave disorders linked to primary VF broadens the mechanistic importance of BrS in sudden cardiac death. It may lie on a spectrum of early repolarisation pathology which is becoming increasingly recognised as a marker of premature cardiovascular death. Mechanistically, abnormalities of both depolarisation and repolarisation in the right ventricular outflow tract, and heterogeneities of conduction between the endocardium and epicardium have been implicated in the electrographic manifestations of BrS and arrhythmogenesis.The initial belief of BrS as a single autosomal dominant ion channel disorder has been challenged. It has become apparent that sodium channel mutations only account for a maximum of 30% of cases and structural myocardial abnormalities have now been described in what was previously thought to be a purely functional condition. It is highly probable that BrS is an umbrella diagnosis for a number of conduction and repolarisation abnormalities which manifest as this syndrome and the coved ST elevation represents the final common pathway of both ion channel and structural derangements. This review will discuss the issues surrounding the mechanisms of lethal arrhythmia in BrS and summarise both basic science and clinical research findings.