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Ann Thorac Surg 2001;71:1069-1070
© 2001 The Society of Thoracic Surgeons
a Division of Cardiothoracic Surgery, The Buffalo General Hospital, 100 High St, Buffalo, NY 14203, USA
e-mail: lisbon5{at}yahoo.com
To the Editor
We read with interest the recent article by Guyton and coworkers [1] on perfusion-assisted direct coronary artery bypass without cardiopulmonary bypass (CPB). This study demonstrated that as off-pump myocardial revascularization gains popularity, new techniques are developed to expand indications for and to increase the safety of coronary artery bypass grafting (CABG) without CPB. In their study, the authors reported 10 patients who underwent multivessel, off-pump CABG with selective perfusion of coronary grafts to maintain hemodynamic stability during cardiac manipulations. This was accomplished by using a pressure-controlled blood delivery system, in which the ascending aorta was used as an inflow source and arterial blood was delivered into individual coronary grafts as distal anastomoses were constructed.
Interestingly, in the same issue of the Annals of Thoracic Surgery, Bedi and colleagues [2] reported their experience on a series of 100 patients undergoing multivessel off-pump CABG in whom continuous retrograde perfusion of arterial blood through the coronary sinus was used. In addition to retrograde perfusion through the coronary sinus, coronary perfusion was enhanced by delivering arterial blood into coronary grafts as distal anastomoses were constructed. In contrast to Guyton and colleagues [1], however, Bedi and associates [2] did not use an active delivery system and therefore risked less predictable coronary perfusion pressures, especially during maximal cardiac elevation.
Although there is little doubt that both studies describe techniques that may increase the safety of off-pump revascularization, an argument can be made as to whether these methods are necessary in the vast majority of patients undergoing multivessel off-pump CABG. Although preservation of hemodynamic stability during cardiac elevation has traditionally represented the main obstacle to multivessel off-pump coronary grafting, in our experience favorable hemodynamics can usually be maintained if a few measures are taken. First, in contrast to the above named authors [1, 2], we routinely begin off-pump multivessel revascularization by grafting the left anterior descending coronary artery (LAD) with the left internal mammary artery (LIMA). Although the ideal sequence of revascularization may vary somewhat from patient to patient, our experience suggests that immediate revascularization of the LAD territory is advantageous, as it can be accomplished with minimal cardiac manipulation. As a result, hemodynamic stability during LAD grafting is usually well preserved and a critical area of myocardium is immediately revascularized as the distal anastomosis is completed. This strategy is likely to enhance left ventricular tolerance to more substantial cardiac elevation as coronary targets on the lateral and inferior walls of the heart are exposed. Importantly, we have noted that the presence of an LIMA-to-LAD graft neither prevents nor hinders the ability to manipulate the heart when additional coronary targets are grafted.
Second, as previously reported [3], we routinely advocate the use of intracoronary shunts during grafting of coronary arteries on the beating heart. In our experience not only does this technique improve visualization, thereby reducing the likelihood of a technical error, but it preserves distal coronary perfusion and prevents distal ischemia. Finally, we note that preservation of hemodynamic stability is greatly dependent on the method employed to accomplish coronary exposure and stabilization. The use of the "single suture" technique [4], which consists of elevating the heart and gaining exposure of various coronary targets by using a single suture through the oblique sinus of the posterior pericardium, in combination with a pressure-type mechanical stabilizer of the new generation (Cardiothoracic Systems, Cupertino, CA) [3], usually allows adequate exposure of difficult coronary targets while preserving cardiac function.
In our experience, cardiac manipulation is associated with profound deterioration of both systolic and diastolic function in only a minority of patients, such as in the presence of severe and diffuse coronary disease or severe left ventricular dysfunction. In such patients, adjunctive measures of coronary perfusion may be advantageous and support the ischemic myocardium during cardiac manipulations. If these methods of coronary perfusion are employed, however, techniques of "passive" perfusion using the ascending aorta as an inflow site [2] should be used with caution as coronary perfusion pressure is greatly influenced by aortic pressure, which may drop when the heart is maximally elevated. We believe that "active" coronary perfusion systems using delivery devices such as the pressure-controlled delivery system used by Guyton and coworkers [1] may have a role in the few patients with diffuse and severe coronary artery disease, or severe left ventricular dysfunction.
References
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