Recurrent Cardiac Arrest in a Pediatric Patient with Hypertrophic Cardiomyopathy and a Myocardial Bridge: Player or Spectator?

Myocardial bridge (MB) is common in patients with hypertrophic cardiomyopathy (HCM), and can reduce coronary flow leading to myocardial ischemia, fibrosis, and malignant ventricular arrhythmias resulting in sudden cardiac arrest (SCA). However, MB has not been previously reported as an isolated, modifiable cause of recurrent SCA in pediatric HCM. To describe a case of HCM with recurrent SCA found to have left anterior descending (LAD) coronary artery MB, with resolution of recurrent SCA after MB unroofing. A 13-year-old male with HCM had an epicardial implantable cardioverter defibrillator (ICD) placed after his first SCA at age 8. Atenolol was started after his second SCA at age 12. After a third SCA he was transitioned to Nadolol and Mexiletine, and underwent transvenous ICD implantation due to delayed shock secondary to under-sensing on epicardial system. He had two additional episodes of SCA, for which he was started on Amiodarone and transferred to our institution for transplant evaluation in the setting of biventricular systolic dysfunction. During transplant evaluation, exercise stress test suggested the presence of ischemia. Cardiac catheterization revealed a 6 cm proximal LAD MB, with near occlusion during systole (Figure 1). He underwent LAD unroofing and remained asymptomatic at baseline activity level with no further episodes of SCA during the subsequent follow-up. MB can cause significant compression leading to compromised coronary flow and myocardial ischemia distinct from the intrinsic underlying cardiomyopathy in HCM. Modifiable causes should be considered in cases of recurrent SCA, as treatment may alter prognostic implications.