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Ann Thorac Surg 1999;68:1094-1095
© 1999 The Society of Thoracic Surgeons

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Pulmonary hypertension during beating heart coronary surgery: intermittent inferior vena cava snaring

^a Department of Surgery, Montreal Heart Institute, Montreal, Quebec, Canada

Address reprint requests to Dr Cartier, Research Center, Montreal Heart Institute, 5000 Belanger St E, Montreal, PQ, H1T 1C8, Canada;
e-mail: cartierr{at}icm.umontreal.ca

	Abstract

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Pulmonary hypertension during beating heart coronary artery bypass grafting may compromise the possibility of safely completing the procedure off-pump. To obviate such a problem, we describe a simple technique by which the inferior vena cava is progressively snared to decrease pulmonary pressure.

	Introduction

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Coronary artery bypass grafting (CABG) without cardiopulmonary bypass (CPB) was first reported by Kolessov [1]. Subsequently, Benetti and Buffolo and their coworkers each published the results of their large series of off-pump coronary bypass procedures [2, 3]. However, this technique did not gain wide acceptance until the advent of mechanical stabilizers, during the mid 1990s, that has contributed to improving the safety and precision of coronary anastomosis [4]. Potential benefits of beating heart coronary artery bypass, such as decreased bleeding, tissue edema, and pulmonary and renal insufficiency, are probably related to a decreased systemic inflammatory response and platelet dysfunction experienced during off-pump CABG as compared with CABG with CPB [5].

At the Montreal Heart Institute, we started performing off-pump CABG in September 1996 and in 1998, we (R.C.) have performed systematic off-pump CABG in 97% (159/163) of coronary artery disease patients, with 1.2% operative mortality and a 3.2% myocardial infarction rate [6]. Absolute contraindications were preoperative hemodynamic instability and deep intramyocardial left anterior descending artery. Relative contraindications were dense posterior adhesions during reoperative procedures and patients with moderate ischemic mitral insufficiency. Patients with mild ischemic mitral insufficiency are subject to increased regurgitation territories during exposure of the obtuse marginal or the right coronary artery. Such an acute increase in regurgitation may jeopardize hemodynamics and compromise safe completion of the procedure without CPB. Similarly, patients with severe left ventricular dysfunction (ejection fraction < 30%) will occasionally experience an unexpected rise in pulmonary pressure during manipulation. These rises in pulmonary artery (PA) pressure are generally due to further ischemic deterioration of the ventricular function blood flow occlusion. The PA pressure rise is followed by a drop in systolic pressure and a significant decrease in myocardial contractility. At that point, the surgeon has to make the decision of either performing a bypass or any other procedure to restore ventricular contractility. We have developed a simple technique to overcome this problem.

	Technique

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In the circumstances previously described, a standard umbilical tape is passed around the inferior vena cava (IVC). If during the procedure the pulmonary pressure increases, the IVC is partially snared until pulmonary pressure returns to basal values. In the advent of high elevation of pulmonary pressures, the IVC may be completely occluded. Clinically, decreasing inflow to the right ventricle through this maneuvering allows rapid normalization of pulmonary pressures with elevation of the systemic pressure and significant improvement of the ventricular contractility. Following completion of the anastomosis, the IVC is gradually unclamped until reestablishment of basal hemodynamics. The IVC crossclamping time is generally kept under 5 minutes.

	Comment

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Precise coronary anastomosis on a beating heart requires excellent exposure and stabilization. Exposure is facilitated by positioning the operating table as well as placement of traction sutures on the posterior pericardium to access the obtuse marginal territory [7]. Beating heart CABG may be difficult to tolerate in patients with low to moderate mitral insufficiency or left ventricular dysfunction. Vertical displacement of the heart during exposure of obtuse marginal vessels may occasionally augment or create mitral insufficiency as well, coronary flow occlusion, and could contribute to left ventricular ischemic dysfunction. In this situation, acute volume overload of the left ventricle further increases mitral regurgitation (MR) by decreasing leaflet coaptation and by inducing posterior papillary muscle dysfunction. This results in subendocardial ischemia secondary to an elevated left ventricle end-diastolic pressure. Temporary partial or total occlusion of the IVC decreases inflow to the right ventricle and lowers pulmonary artery pressure. It inhibits left ventricle dilatation, preserves left ventricular geometry, and ultimately, temporarily improves forward stroke volume. Furthermore, it gives time to the anesthesiologist to reappraise the pharmacologic support (generally intravenous nitroglycerin) and regain control of the hemodynamics. Contrary to apposition of a vascular clamp on the IVC, a snare allows easy control of the amount of IVC occlusion desired. Furthermore, the level of occlusion may be easily modified throughout the procedure even when access to the IVC is difficult, such as that encountered during exposure of the obtuse marginal artery. However, this procedure should not be seen as a surrogate for mitral valve surgery and, in any case, should not interfere with the surgeon’s decision to fix or not fix the mitral valve. This procedure should be seen as a temporary maneuver to help manage unexpected rises in pulmonary pressure. In order to evaluate the need for a surgical correction of ischemic mitral insufficiency, we have adopted the following protocol. Patients with moderate ischemic MR are first evaluated by transoesophageal echocardiography in the operating room prior to the surgery. A stress test with boluses of phenylephrine is carried out in order to obtain a 50% increase of systemic pressure. This generally will lead to a significant rise in pulmonary pressure. The MR is then carefully scanned. If in any circumstance the MR increased to a moderate to severe grade (systolic flow in pulmonary veins), a mitral annuloplasty is undertaken on CPB in adjunct to coro-nary artery revascularization. Otherwise, the procedure will be carried out as an off-pump procedure.

In conclusion, in patients with low-to-moderate mitral insufficiency in whom mitral surgery is not found necessary, or in patients with severe ventricular dysfunction, beating heart CABG may exacerbate mitral regurgitation or left ventricular dysfunction and induce hemodynamic instability. In this situation, intermittent partial or complete occlusion of the IVC with an umbilical tape snare enables the surgeon to pursue an operation with stable hemodynamics.

	References

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1. Kolessov V.I. Mammary artery-coronary artery anastomosis as method of treatment for angina pectoris. J Thorac Cardiovasc Surg 1967;54:535-544.[Medline]
2. Benetti F.J., Naselli G., Wood M., Geffner L. Direct myocardial revascularization without extracorporeal circulation. Experience in 700 patients. Chest 1991;100:312-316.[Abstract/Free Full Text]
3. Buffolo E., Andrade J.C.S., Succi J.E., et al. Direct myocardial revascularization without cardiopulmonary bypass. Thorac Cardiovasc Surg 1985;33:26-29.[Medline]
4. Shennib H., Lee A.G.L., Akin J. Safe and effective method of stabilization for coronary artery bypass grafting on the beating heart. Ann Thorac Surg 1997;63:988-992.[Abstract/Free Full Text]
5. Brasil L.A., Gomes W.J., Salomão R., Buffolo E. Inflammatory response after myocardial revascularization with or without cardiopulmonary bypass. Ann Thorac Surg 1998;66:56-59.[Abstract/Free Full Text]
6. Cartier R., Braun S., Martineau R., Leclerc Y. Systematic coronary artery revascularization without cardiopulmonary bypass. Can J Cardiol 1998;14(Suppl F):108F.
7. Cartier R., Blain R. Off-pump revascularization of the circumflex artery. Ann Thorac Surg 1999;68:94-99.[Abstract/Free Full Text]

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Raymond Cartier Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Dagenais, F. Articles by Cartier, R. Search for Related Content PubMed PubMed Citation Articles by Dagenais, F. Articles by Cartier, R.