Venous valves: Unseen obstructions to coronary access

Navigation within the coronary venous system has become increasingly important in commonly employed cardiovascular interventional procedures, including cardiac resynchronization therapy. While cannulating the coronary sinus ostium can be challenging due to the presence of the Thebesian valve, venous valves within the coronary venous system may hinder advancement of guide wires, catheters or pacing leads [ 1]. While presence and development of these venous valves is variable, a venous valve in a patient could potentially complicate a cardiovascular interventional procedure. However, the functional anatomy of coronary venous valves remains not well understood because they cannot typically be visualized with fluoroscopy. Human hearts ( n= 4) deemed not viable for transplantation were studied using a previously described isolated heart preparation that allows direct visualization of intracardiac anatomy [ 2]. Endoscopic cameras ( 6 mm) and fiberscopes ( 1.4 mm) were employed to obtain real- time imaging of various venous valves. The relative coverage of venous ostia varied greatly in these four hearts; examples of highly variable venous valves are described here. In one heart, a unicuspid valve covered approximately two- thirds of the posterior interventricular venous ostium. Another unicuspid valve covered three- fourths of the posterior vein of the left ventricle ostium. Difficulty in implanting devices in the coronary venous system with functioning venous valves was observed and a unicuspid valve of Vieussens partially covered the great cardiac vein ostium.