Paddling through palpitations: when genes, myocardial inflammation and exercise collide-a case report of arrhythmogenic cardiomyopathy in a young competitive rower.

Background: Arrhythmogenic cardiomyopathy (ACM) is characterized by fibrofatty replacement of myocardium, predisposing to ventricular arrhythmias and sudden cardiac death. Arrhythmogenic cardiomyopathy is often linked to desmosomal gene mutations, particularly PKP2, which encodes plakophilin-2, a key structural protein in cardiac intercalated discs. In individuals with PKP2 mutations, exercise has been shown to accelerate disease progression. Case summary: A 22-year-old male semi-professional rower presented with palpitations, pre-syncope, and a history of presumed myocarditis with subepicardial fibrosis on cardiac magnetic resonance (CMR). Workup revealed anterior T-wave inversions on resting ECG and sustained monomorphic right ventricular (RV) outflow tract tachycardia, induced during exercise testing. Repeat CMR showed RV dysfunction and non-ischaemic RV and LV fibrosis with fibrofatty replacement. The patient met diagnostic criteria for biventricular ACM and underwent catheter ablation targeting the arrhythmic substrate. A multidisciplinary team carefully considered ICD therapy. However, due to the limited extent of the arrhythmic substrate, the exercise-induced nature of the ventricular tachycardia, and the successful ablation, ICD implantation was deferred at this stage. An ILR was implanted for continuous rhythm monitoring, with a low threshold for future ICD placement. High-intensity sports restriction, pharmacological therapy, and genetic counselling were initiated. Genetic testing identified a pathogenic PKP2 mutation. Discussion: This case highlights the complex interplay of genetic predisposition, myocardial inflammation, and exercise in ACM expression. The presumed myocarditis likely represented a 'hot phase' of ACM, accelerating structural cardiac changes. High-intensity exercise then acted as a 'second hit,' triggering phenotypic expression. Multidisciplinary evaluation combining rhythm monitoring, imaging, and genetic testing was key to diagnosis and management.