We describe a case of a 54-year-old female referred for ablation of supraventricular tachycardia (recurrent episodes under anti arrhythmic therapy). During a first procedure catheters progressed on the left side of the spine draining to the superior vena cava. Multi-row detector CT angiography revealed infrahepatic interruption of the inferior vena cava with venous blood drainage into the superior vena cava, via the azygos venous system, a previously unknown asymptomatic anomaly. Ablation was subsequently performed successfully using a mixed approach via the right suclavian vein (ablation catheter) and the azygos venous system (diagnostic catheter in the coronary sinus).