Partially unroofed coronary sinus and persistent left superior vena cava: intracardiac echocardiographic observation

Unroofed coronary sinus, a rare congenital anomaly first described by Raghib and colleagues1 in 1965, is a result of an embryologic error involving imperfect or complete failure of development of the left atriovenous fold, which is manifested as a focal (fenestration or partial unroofing of the coronary sinus) or complete absence of the coronary sinus septum. Before the era of echocardiography, precise diagnosis of this anomaly was possible only during surgical procedure or at autopsy. Since the advent of the echocardiography, several studies have reported the usefulness of two-dimensional transthoracic and transesophageal echocardiography in the diagnosis of unroofed coronary sinus. We describe the intracardiac echocardiographic delineation of partially unroofed coronary sinus and persistent left superior vena cava in a patient with atrioventricular nodal reentrant tachycardia. Incidental finding of the dilated coronary sinus during radio frequency ablation of the tachycardia led to the diagnosis of this unusual anomaly.