Abstract 4358805: Silent Fibrosis, Loud Signals: Early-Onset Atrial Arrhythmias as the Sentinel of Familial Restrictive Cardiomyopathy

Background: Restrictive cardiomyopathy (RCM) is a rare cardiac condition characterized by stiff and noncompliant ventricular walls, leading to impaired diastolic filling and normal or near-normal systolic function. This condition often presents with subtle symptoms of heart failure. We present a compelling case of longstanding atrial fibrillation (Afib) and atrial flutter (AFL) culminating in refractory cardiogenic shock, ultimately revealing an undiagnosed restrictive cardiomyopathy. Case: A 40-year-old male with a history of persistent Afib and AFL, unremarkable cardiac MRI on first occurrence for atrial arrhythmias, presented with dyspnea, dizziness, fatigue, and palpitations while on dofetilide. He was found to have atypical AFL with a rapid ventricular response, refractory to pharmacological and electrical cardioversion. His arrhythmia history included multiple catheter ablations for recurrent atrial fibrillation: pulmonary vein and posterior box isolation, anterior wall homogenization, mitral annulus flutter ablation as well as focal atrial tachycardia ablation in the coronary sinus. His family history revealed a sister with refractory Afib at age 30, later diagnosed with restrictive cardiomyopathy, who underwent orthotopic heart transplantation (OHT) at age 44. On admission, echocardiography revealed severe right atrial enlargement and grade III diastolic dysfunction. Attempts at rate and rhythm control with multiple agents were unsuccessful. On day 2 of admission, he developed cardiogenic shock (CI 1.5, RA 20, PCWP 40, PA 50/30 [mPA 40], PVR 3, CPO 0.53, PAPI 1.0), necessitating V-A extracorporeal membrane oxygenation and Impella CP for circulatory support. Discussion: RCM often eludes early detection due to its presentation with preserved ejection fraction and relatively subtle heart failure symptoms. However, Afib or AFL refractory to ablation or cardioversion may serve as an early indication, especially in the context of a strong family history. We suspect progression of cardiomyopathy in this patient who, years ago, had a normal cardiac MRI. Identifying RCM through advanced imaging or genetic screening is crucial, as it enables early consideration of interventions, such as evaluation for OHT, which may prevent catastrophic outcomes. Proactive screening and repeat imaging, such as cardiac MRI, in patients with incessant atrial arrhythmias who also have a significant familial burden, can mitigate delays in treatment and improve prognosis.