Central: Direct Aortic Cannulation
Over the last decade several centers have shown feasibility and safety of direct aortic cannulation even in an acutely dissected aorta13, 28, 29. This technique allows a more rapid initiation of cardiopulmonary bypass and offers the benefits of proximal antegrade perfusion of the true lumen. Many surgeons use this approach preferentially in the setting of hemodynamic instability and when preoperative imaging shows a severe dissection/disruption of the innominate artery. In most patients an anteriorly positioned true lumen is observed which allow easy accessibility of the true lumen via a needle and wire under echocardiographic guidance 27. Other surgeons use this technique routinely even when the innominate artery is not dissected and the true lumen is more posteriorly positioned, reporting excellent results 13. Frederick and colleagues have described 3 types of anatomy relevant to direct aortic cannulation of the true lumen (Figure 1) ; Level 1 comprises those patients, in whom a portion of the true lumen is identifiable and accessible anteriorly in the ascending aorta; Level 2 are those patients in whom the true lumen is posterior and the false lumen is anterior while Level 3 are those patients in whom a complete or nearly complete circumferential dissection of the aorta occurs, resulting in a free-floating ascending aorta true lumen, which expands during ventricular systole and contracts during diastole. While Level 1 provides for easy access (Figure 2), Level 2 and 3 would require the needle to traverse through the false lumen, and puncture the intimal-medial flap into the true lumen (Figure 3).
Some surgeons hesitate to cannulate the ascending aorta directly due to concerns about possible rupture during cannulation. This is mostly not observed 29. The cannulation site is eventually excised at the time of circulatory arrest during open arch repair. At the conclusion of the open arch repair/replacement, the arch Dacron graft is directly cannulated to resume antegrade cardiopulmonary bypass.