Homozygous mutation in SCN5A associated with atrial quiescence, recalcitrant arrhythmias, and poor capture thresholds

Abstract

Case report A 6-year-old Hispanic girl was referred to cardiology for irregular heartbeats. On electrocardiogram (ECG), she was noted to have sinus bradycardia with nonspecific intraventricular conduction delay, as well as frequent sinus pauses with junctional escape on Holter monitoring. Despite multiple attempts to contact her, she did not follow up, and at 11 years of age collapsed while running at school. She was unresponsive, and an automated external defibrillator determined her rhythm to be “shockable” ventricular tachycardia. After defibrillation, perfusion was re-established, and she was taken to a local emergency room, where a lidocaine infusion was initiated with temporary stabilization in her rhythm. While in the emergency room, she had recurrent episodes of unstable, sustained ventricular tachycardia, requiring 6 separate cardioversions and ongoing cardiopulmonary resuscitation. A chest radiograph showed moderate cardiomegaly. Electrocardiography revealed no discernible atrial activity, with a slow junctional escape and frequent premature ventricular contractions (Fig. 1). It also revealed low-voltage QRS complexes and a prolonged QT interval, although this was after cardiac arrest. Subsequent telemetry revealed frequent episodes of polymorphic ventricular tachycardia. An echocardiogram was performed, which revealed severely depressed biventricular function (ejection fraction 19%), with normal anatomy and coronary origins. Because of recurrent episodes of ventricular tachycardia/ventricular fibrillation, she was transitioned to an amiodarone infusion. She was transferred to our institution and was ultimately placed on extracorporeal membrane oxygenation for recalcitrant arrhythmias and progressive metabolic acidosis. In the operating room, it was noted that her atria were dilated and not contracting.