Successful percutaneous cardiac resynchronization despite an occlusive Thebesian valve

We report the case of a patient with symptomatic heart failure referred after an unsuccessful attempt at cardiac resynchronization therapy. An occlusive Thebesian valve prevented entry into the coronary sinus ostium. Careful analysis of the patient's cardiovascular physiology and anatomy revealed the "fortuitous" presence of a persistent left superior vena cava. Cannulation of this vessel permitted percutaneous retrograde placement of a left ventricular lead into a posterolateral cardiac venous branch resulting in successful cardiac resynchronization. This unique case provides strong evidence that thorough knowledge of cardiac embryology, anatomy, and physiology plays a pivotal role in percutaneous electromechanical intervention for drug-refractory heart failure.