Abstract 10897: Severe Atrial Dysfunction and Sick Sinus Syndrome in a Patient With Scn5a Mutation

Abstract

Introduction: SCN5A mutations are associated with numerous cardiovascular conditions, including dilated cardiomyopathy, atrial fibrillation, and sick sinus syndrome. Specific variants in patients with severe atrial dysfunction may be associated with increased risk of stroke even in young patients. Case: This case describes a previously healthy 38-year-old male of French descent who presented with intermittent palpitations and presyncope associated with atrial flutter followed by prolonged conversion pauses up to 7.5 seconds, then followed by junctional bradycardia. Echocardiogram showed a mildly dilated left atrium. Electrophysiology study demonstrated extensive scarring in the left atrium with normal sinus node function and right atrial voltage. No atrial fibrillation was noted. He was also found to have typical atrial flutter and mitral flutter. He underwent cavotricuspid isthmus ablation and mitral annular flutter ablation. Due to his vagal-mediated pauses and junctional rhythm, he also underwent cardioneuroablation aimed at partial denervation. Following this, he had further episodes of junctional rhythm on the days after exercise. He underwent further total cardioneuroablation and was found to have progressive scarring at the sinus node area and sinus node dysfunction, so a permanent pacemaker was placed. He underwent genetic testing which demonstrated SCN5A heterozygous missense pathogenic variant c.2823G>A. Conclusion: The SCN5a gene encodes the alpha subunit of the cardiac sodium channel, which is responsible for initiation and propagation of action potentials. SCN5A variants are associated with a number of cardiovascular conditions. There are reports of stroke in young French patients with severe atrial dysfunction and SCN5A mutations, including variant c.2823G>A, demonstrating that severe atrial dysfunction is a risk factor for stroke regardless of CHADS2VASc score, and specific SCN5A mutations may be associated with increased risk of stroke. Given these reports and absence of relevant guidelines, apixaban was continued indefinitely for prevention of stroke. At follow-up two months later, the patient resumed physical activity and reported symptomatic improvement, without any episodes of syncope or near syncope.