The surgical importance of a persistent left superior vena cava.

or indirectly by way of the coronary sinus. The embryology and frequency of this configuration have been reviewed in a previous communication (Hurwitt, Escher and Citrin, 1955). Since anomalies of the heart and great vessels tend to occur in association, one may encounter a left superior vena cava draining into the right atrium in the process of other operations, such as in the correction of a patent ductus arteriosus. Under such circumstances the anatomical course of the left superior vena cava is such that it does not interfere with the stated operation, and the vein usually has no surgical importance. With the advent of open heart surgery, however, employing either cardiopulmonary by-pass or hypothermia, a left superior vena cava assumes real surgical significance, regardless of whether it drains into the right or left atrium. Failure to identify and mobilize this vessel, with temporary occlusion for hypothermia and cannulation or occlusion during cardiopulmonary by-pass, may seriously compromise the procedure. The necessity for this manoeuvre has been described in a number of articles, including one from this department (Robinson, Glotzer, Gilbert, Escher and Hurwitt, in press). Left Superior Vena Cava Entering Left Atrium. As a contributing cause of cyanosis, the importance of drainage of any systemic vein into the left auricle has usually been overshadowed by the severity of associated cardiac defects. Subsequent to the summary of the reported cases (Hurwitt et al., 1955), two additional such patients have come to surgery at this hospital.