Diagnostic value of exercise-induced ventricular extrasystoles with right bundle branch block morphology in identifying myocardial fibrosis in left ventricular arrhythmogenic cardiomyopathy

Introduction The diagnosis of left ventricular arrhythmogenic cardiomyopathy (LVAC) is based on phenotypic, genetic, and family history criteria. Recently, the detection of exercise-induced ventricular extrasystoles with right bundle branch block morphology (RBBB-VE) has been proposed as a minor criterion for LVAC, although it is not specific to this condition. Purpose Our objective was to evaluate the diagnostic value of RBBB-VE during exercise testing in identifying myocardial fibrosis, measured through late gadolinium enhancement (LGE), and its association with severe clinical events. Methods A cross-sectional study was conducted on 103 individuals, divided into three groups: LVAC (n=63), non-arrhythmogenic dilated cardiomyopathy (DCM, n=20), and healthy controls (n=20). Clinical and exercise testing parameters were assessed. Univariate statistical tests (Fisher’s exact test and Wilcoxon test) were used to compare the prevalence of RBBB-VE between groups. Additionally, logistic regression models were adjusted to determine the independent association between RBBB-VE and fibrosis. Results Baseline characteristics are shown in Table 1. The prevalence of RBBB-VE was 63.8% in LVAC compared to 21.1% in DCM (p<0.001). Its sensitivity and specificity for detecting fibrosis were 60.98% and 66.67%, respectively (Figure 1). In a logistic regression model adjusted for LVAC patients, the presence of RBBB-VE was independently associated with fibrosis (odds ratio [OR]=10.22; p=0.0258). Additionally, each unit increase in left ventricular ejection fraction on magnetic resonance imaging increased the odds of fibrosis by 12.3% (OR=1.123; p=0.007). A trend toward a higher incidence of arrhythmic events was observed in patients with RBBB-VE, with post hoc differences between subgroups (p=0.042). Conclusions The presence of RBBB-VE during exercise testing has moderate diagnostic value for fibrosis in LVAC, with a sensitivity of 61% and a specificity of 67%, showing a significant association with an increased risk of fibrosis (OR=10.22) and a tendency towards a higher incidence of arrhythmic events. These findings support the use of exercise-induced RBBB-VE as a useful marker for risk stratification in this population.Table 1.Baseline characteristics. Fig 1.ROC curve. RBBB-VE for fibrosis.