Pacemaker implantation in a challenging anatomy: isolated persistent left superior vena cava and azygos continuation of interrupted inferior vena cava

Key Clinical Message Isolated persistent left superior vena cava (SVC) in the absence of right SVC is a rare congenital variant of thoracic venous drainage with the left subclavian and jugular veins that drain into the right atrium through the coronary sinus. Inferior vena cava interruption with azygos continuation is another congenital anomaly resulting in venous drainage of the lower extremities via a typically dilated azygos vein. Although both variants are generally asymptomatic and incidentally detected, these can have clinical implications in specific circumstances and in particular during device implantation. We report a case of pacemaker implantation in which both anatomical variants were present.