Atrial fibrillation with progressive left ventricular dysfunction: what lies beneath the tip of the iceberg (clinical case)?

The simultaneous detection of atrial fibrillation (AF) and left ventricular (LV) dysfunction raises questions about their relationship and necessitates a nosological diagnosis. This case study presents a 39-year-old patient who has had recurrent AF and moderate LV systolic dysfunction. Concomitantly, the patient has experienced sinus bradycardia, a transient left bundle branch block (LBBB), and prolonged QTc, which precluded the use of antiarrhythmic medication. In 2018, successful radiofrequency ablation (RFA) for paroxysmal AF was performed. However, in 2023, the patient experienced anginal pain, with a reduced ejection fraction to 26%, and persistent AF. After cardioversion, LV dysfunction persisted, and a myocardial biopsy revealed active, virus-negative, lymphocytic myocarditis (LM). The patient was prescribed immunosuppressive therapy, including corticosteroids and azathioprine. Despite recurrent tachyarrhythmic AF, LV dysfunction regressed. A epeat RFA was performed in 2024 but was clinically unsuccessful. Whole-exome sequencing revealed a variant in the RBM20 gene, suggesting that investigating the etiology of AF in patients with LV dysfunction may improve the efficacy of AF treatment and influence the course and outcomes of the underlying disease, which can be obscured by the diagnosis of «idiopathic» AF.

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