Azygos Vein ICD Lead Implantation Lowers Defibrillation Threshold in a Patient with Hypertrophic Cardiomyopathy

A 14-year-old boy with hypertrophic cardiomyopathy (HCM) diagnosed at the age of 1 year and with massive left ventricular hypertrophy suffered an episode of ventricular fibrillation during mild effort. He underwent a dual-chamber implantable cardioverter defibrillator (ICD) implantation. The defibrillation threshold testing (DFT) was ineffective. Subcutaneous multi-coli arrays tunneled into the left postero-lateral position and connected to the superior vena cava (SVC) port of the dual-chamber ICD were added to increase the myocardial mass involved in the defibrillation shock pathway. A new DFT was unsuccessful. The patient was transferred to our hospital for myectomy. An epicardial defibrillation patch was placed on the left ventricular lateral wall, but again, DFT testing was ineffective using the right ventricular (RV) coil to lateral patch as shock pathway. Another epicardial defibrillation patch was then placed on the inferior wall. In this case, DFT testing was effective with a defibrillation pathway between the two patches and the can. In November 2015, a high shock impedance alarm was recorded through remote monitoring, thus compromising the safety of the ICD shock pathway. The patient underwent the implant of a new trans-venous defibrillation coil lead in the azygos vein. After few months, the patient developed symptomatic severe aortic regurgitation and underwent an aortic valve replacement. During the operation, DFT testing was performed and was successful. Our case illustrates that azygous vein ICD lead implantation is efficacious in HCM with massive hypertrophy and high DFT, and prompts further studies to systematically investigate its efficacy in this particular subgroup of the HCM population.