While the cardiac structural and functional phenotypes were similar at baseline in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC) with desmosomal variants and those with genotype-negative exercise-induced arrhythmogenic cardiomyopathy (EiAC), progression to RV dilatation and dysfunction was observed only in those with ARVC over long-term follow-up, according to results from a recent study published in JACC: Cardiovascular Imaging. The incidence of life-threatening ventricular arrhythmias (VAs) was high and similar between groups.

In the longitudinal cohort study, Linda T. Aaserud, MD, et al., included 125 patients with ARVC (half were women, average age 38 years) and 41 patients with EiAC (six women, average age 45 years) and followed them for 96 months and 82 months, respectively.

The EiAC patients included competitive endurance athletes (>24 MET-hours/week for more than six consecutive years) without inherited or genetic factors and referred due to VAs. Disease progression was assessed by repeat echocardiographic examinations and incident VA during follow-up.

An analysis of 730 echocardiographic examinations revealed that RV structure and function deteriorated in ARVC patients but remained stable in EiAC patients. Furthermore, five-year and 10-year cumulative incidences of VA were similar between the two groups, at about 22% at five years and increasing only slightly at 10 years.

The results suggest, write the authors, that patients with EiAC may have a greater morphological reserve that leads to less disease progression but does not protect against arrhythmic events. Noting the "high incidence of life-threatening VA" with results similar with patients with ARVC, they add: "The findings indicate that EiAC patients may need close follow-up regardless of structural and functional disease progression..."

"Ventricular arrhythmias are relatively common in middle-aged endurance athletes, and the greatest challenge in the translation to the clinic will be in trying to determine which additional clinical features are required for a diagnosis of EiAC," write André la Gerche, MD, and Hein Heidbuchel, MD, PhD, in an accompanying editorial comment. "Without more rigorous diagnostic criteria, some healthy athletes will be inappropriately treated and be advised against sports continuation while other athletes with a propensity to serious arrhythmias will go unrecognized."