Abstract Body (Do not enter title and authors here): Introduction: Pregnancy-induced cardiomyopathy is typically idiopathic, with no predisposing condition identified. In some cases, women with pre-existing genetic mutations may initially present with cardiomyopathy in pregnancy.

Case: A 30-year-old G2P1001 woman presented to Labor & Delivery with frequent palpitations, dyspnea on exertion, and reduced exercise tolerance in the third trimester. Her previous pregnancy was complicated by frequent premature ventricular contractions (PVCs) but otherwise unremarkable. She had a family history of early-onset atrial fibrillation in her mother and a maternal cousin with pregnancy-induced arrhythmias. ECGs and telemetry demonstrated significant ectopy (bigeminy, non-sustained ventricular tachycardia) and atrial arrhythmias including supraventricular tachycardia, atrial tachycardia, and atrial fibrillation (Figure 1). Transthoracic echocardiogram (TTE) showed an ejection fraction (EF) of 20-25%, reduced from 50% 2 weeks prior. Ectopy was associated with reduced fetal heart rate variability suggestive of fetal malperfusion, for which an urgent C-section was performed at 38 weeks and 6 days. Following delivery, she was started on amiodarone, metoprolol, and spironolactone, as part of guideline-directed medical therapy. Subsequent TTEs showed improvement in EF to 30-35% at 2 days and 45-50% at 4 weeks postpartum. Cardiac MRI showed no evidence of fibrosis or inflammation. Given her maternal family history of arrhythmic events, genetic testing was pursued. Genetic testing revealed a pathogenic SCN5A variant (c.638G>A (p.Gly213Asp)).

Discussion: SCN5A variants are associated with dilated cardiomyopathy, conduction disorder, and arrhythmias. It is a rare variant of pregnancy-induced cardiomyopathy. This case highlights the value of genetic testing in patients with significant arrhythmia burden and cardiomyopathy in pregnancy and a family history of cardiomyopathy and arrhythmias. For pregnant women with genetic variants predisposing to arrhythmias and cardiomyopathy, comprehensive longitudinal, multidisciplinary care is essential at a referral center with Cardio-Obstetrics expertise and an Inherited Heart Disease Clinic.