The accompanying modified mid-esophageal four-chamber transesophageal echocardiography image shows two coronary sinuses emptying into the right atrium where normally there is one. As shown in panel A, both sinuses run parallel in the AV groove inferior to the left atrium (Supplemental Digital Content, https://links.lww.com/ALN/C43). This rare anomaly, referred to as “double-barrel coronary sinus,” was discovered during a coronary artery bypass graft procedure in which retrograde cardioplegia was planned. Double-barrel coronary sinus arises when the great cardiac vein fails to combine with the left horn of the sinus venosus during the 10th week of development, and is described in full elsewhere.1–3  Despite the obvious perils of cannulating the “false” sinus, criteria for determining the “true” coronary sinus by transesophageal echocardiography have not yet been published.2 

Panel B shows both sinuses en face from the right atrium, with the cephalad sinus (red arrow) appearing slit-like, as described previously.2  The caudad sinus (green arrow) appeared larger in diameter, and its color Doppler flow was greater. Because the “true” coronary sinus should drain a larger myocardial territory and thus have the larger caliber and flow, the retrograde cardioplegia catheter was guided into the caudad sinus with good result. In cases of double-barrel coronary sinus, the authors suggest larger vessel caliber (preferably assessed by three-dimensional imaging in an en face view) and greater Doppler flow to be important determinants of the “true” sinus.

The author declares no competing interests.

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