Persistent left superior vena cava (PLSVC) is the most common variation of anomalous venous return to the heart and present in 0.1–0.5% of the general population. The left anterior cardinal veins typically obliterate during early cardiac development but failure of involution results in PLSVC. It is an asymptomatic congenital anomaly, usually discovered while performing interventions through the left subclavian vein or during cardiovascular imaging. PLSVC can be associated with cardiac arrhythmias and congenital heart disease. We present two cases of PLSVC: first, a 68-year-old male who presented with complete heart block, for which a temporary pacemaker was initially inserted followed by a permanent pacemaker; second, a 53-year-old female with a history of hypertension and ischemic cardiomyopathy with a left ventricular ejection fraction of 25%, and a survivor of sudden cardiac death, who underwent an implantable cardioverter-defibrillator (ICD) for secondary prevention. Both cases of PLSVC were detected incidentally during the transvenous approach to the heart. PLSVC was suspected by the unusually left medial position of the lead, while cineflouroscopy showed the venous trajectory toward the coronary sinus and drainage into the right atrium. It is technically difficult to cross the wire through the tricuspid valve when coming from the PLSVC and coronary sinus without making a loop in the right atrium, which is known as a wide loop technique. PLSVC is an uncommon anomalous anatomical variant and should be recognized appropriately by specialists who frequently carry out procedures through the left subclavian vein, such as implantation of permanent pacemaker, ICD and cardiac resynchronization therapy. It should also be recognized that wide loop formation of the right ventricular lead in the right atrium is helpful to cross the tricuspid valve and to affix the lead in the right ventricle.
Coronary Sinus Draining into the Left Subclavian Vein through a Persistent Left Superior Vena Cava