Familial Symptomatic Sinus Bradycardia: Autosomal Dominant Inheritance
Symptomatic sinus bradycardia, due to either sick sinus syndrome or vagotonia, can be familial, affecting several members of a family. We report an 18-year-old male patient with palpitations and limited exercise capacity who was noted to have severe sinus bradycardia. His resting heart rate was 40/min, with normal PR and corrected QT intervals, and sinus pauses up to 6 seconds during sleep. Exercise treadmill test and pharmacologic autonomic blockade during electrophysiologic studies abolished the bradycardia, suggestive of vagotonia rather than intrinsic sinus node dysfunction. This patient's father and a female cousin had a similar clinical history but associated with syncope and severe sinus bradycardia. The mode of transmission appeared to be autosomal dominant. All three have permanent demand pacemakers implanted and are asymptomatic.
Mehta, A. V.; Chidambaram, B.; and Garrett, A.. 1995. Familial Symptomatic Sinus Bradycardia: Autosomal Dominant Inheritance. Pediatric Cardiology. Vol.16(5). 231-234. https://doi.org/10.1007/BF00795713 PMID: 8524708 ISSN: 0172-0643