Volume 11, Issue 2 , Pages 90-104, Summer 2006
Off-Pump Coronary Revascularization: Operative Technique
Article Outline
Off-pump coronary artery bypass grafting can be performed in most patients undergoing surgical myocardial revascularization. The selection of patients for off-pump surgery is dependent on the surgeon’s knowledge and comfort with the techniques of off-pump revascularization. Early in a surgeon’s experience with off-pump revascularization, it is best to select patients with normal left ventricular size and function, relatively large epicardial coronary arteries free of diffuse calcific atherosclerosis, and coronary artery disease limited to the left anterior descending and right coronary artery systems. As the surgeon gains experience and confidence with off-pump techniques, patients with decreased left ventricular function, enlarged hearts, and coronary artery disease of the circumflex system may be performed off-pump. When the surgeon has mastered the techniques of off-pump coronary surgery, nearly all patients presenting for coronary revascularization may be considered, including those with severe left main coronary artery stenosis, poor left ventricular function, and intramyocardial coronary arteries. Relative contraindications to off-pump myocardial revascularization include patients with severely enlarged and dysfunctional hearts, mitral insufficiency, or small and diffusely diseased coronary arteries. Patients with hemodynamic instability and those with chest anatomy that prevents rightward displacement of the heart, such as pectus excavatum or previous left pneumonectomy, should not be selected for off-pump revascularization.
Similar to on-pump coronary artery bypass grafting, off-pump myocardial revascularization is a complex operation composed of many steps. The operative steps of off-pump coronary artery revascularization are (1) incision and conduit preparation; (2) patient positioning; (3) target vessel exposure; (4) target vessel stabilization; (5) target vessel hemostasis and ischemia prevention; (6) construction of anastomoses; and (7) closure.
Off-pump myocardial revascularization has the potential benefit of lowering the risk of coronary surgery by eliminating cardiopulmonary bypass and ascending aortic manipulation. The use of in situ and composite arterial grafts for coronary revascularization avoids the need for ascending aorta manipulation to construct proximal anastomoses. In this article, the techniques used in off-pump, multivessel coronary artery bypass grafting with in situ and composite arterial grafts is illustrated.
Operative Technique
Figure 1.
The coronary revascularization is performed through a median sternotomy. This approach has multiple advantages. First, both internal thoracic arteries and gastroepiploic artery can be easily harvested through this incision for use as bypass conduits. Second, access to all of the coronary arteries for complete revascularization is obtained with a median sternotomy. Third, in the rare event that conversion to on-pump surgery is necessary, it can be quickly accomplished via this approach. After completion of the median sternotomy, the left and right internal thoracic arteries are harvested with the assistance of an external, elevating retractor. The internal thoracic arteries are harvested in a skeletonized manner to better preserve the blood supply of the sternum.
Figure 2.
After the internal thoracic arteries are dissected from the chest wall, the harvesting of the gastroepiploic artery is begun by incising the upper peritoneum and delivering the stomach and omentum into the mediastinum. The gastroepiploic artery is harvested as a pedicle by dividing and ligating its branches to the stomach and omentum. The dissection of the gastroepiploic artery begins at the pylorus and extends along the greater curvature of the stomach. After the patient is heparinized, the distal end of the gastroepiploic artery is divided and the artery is wrapped in a papeverine-soaked sponge.
Figure 3.
After the conduits are harvested, the thymus is divided and ligated and the pericardium is incised from the innominate vein to the diaphragm. The pericardium is also incised parallel and 1 cm from the diaphragm anteriorly to the patient’s left and right. An additional vertical incision is made in the pericardium on the left, just lateral to the pulmonary artery. The left internal thoracic artery is later routed through this left-sided pericardial incision, under the upper lobe of the left lung. The patient is heparinized and the left internal thoracic artery is prepared as an in situ graft by dividing it distally and the right internal thoracic artery is prepared as a free graft by dividing it both proximally and distally. The proximal anastomosis of the free right internal thoracic artery graft is performed to the left internal thoracic artery in a “T” fashion. The location of the right internal thoracic artery to left internal thoracic artery anastomoses is just distal to where the left internal thoracic artery is expected to enter the pericardial space.
Figure 4.
Before performing the distal coronary anastomoses, the patient is placed in a Trendelenberg position and rotated to the right. These positioning maneuvers assist in maintaining patient hemodynamics by augmenting cardiac output. In addition, they assist in coronary artery exposure. With Trendelenberg position and rightward rotation, the heart begins to “fall” out of the chest, bringing the apex out of the chest, beginning to expose the lateral, inferior, and posterior surfaces of the left ventricle.
Figure 5.
The sequence of grafting during off-pump revascularization is often important. Grafting the left anterior descending artery with the in situ left internal thoracic artery first has the advantage of revascularizing a large area of myocardium with minimal myocardial positioning and a single anastomosis. Also, revascularizing the left anterior descending first appears to help the heart tolerate the more aggressive myocardial positioning necessary for lateral and inferior wall revascularization. This is particularly important in patients with critical left main stenosis.
To expose the left anterior descending artery, a left-sided pericardial suture is placed on tension. It is very important not to place any pericardial sutures on the right. They can compress the right ventricle and decrease cardiac output. The left-sided pericardial suture rotates the heart to the right, presenting the left anterior descending in the operative field. To stabilize the coronary artery at the planned anastomoses site, the two arms of a suction stabilizer are placed on either side of the left anterior descending coronary artery and suction is applied. This holds the coronary artery between the arms of the stabilizer motionless.
Figure 6.
To have adequate visualization during construction of the distal anastomosis, the anastomosis site should be bloodless. A single, soft silastic vessel loop is placed around the coronary artery just proximal to the site of the planned anastomosis. The silastic vessel loop is placed on mild tension. To assist in holding the artery open after the arteriotomy, two fine sutures are placed on both sides of the coronary artery in the epicardium and placed on tension.
Figure 7.
If occlusion of the coronary artery results in myocardial ischemia with ventricular ectopy or hemodynamic instability, an intravascular shunt can be used to restore blood flow distal to the arteriotomy. Shunts are also useful in obtaining a bloodless field while performing the distal coronary anastomosis. The shunt is inserted by placing one end in the arteriotomy and advancing the shunt distally until the entire shunt is intravascular. The shunt is then drawn back proximally so it spans the entire arteriotomy with one end of the shunt proximal and the other end distal to the arteriotomy. A humidified carbon dioxide blower is used as opposed to suction to assist with visualization during construction of the distal anastomosis. The misted fluid should be pH-balanced, and carbon dioxide flow should not be more than 4 L per minute to avoid coronary artery or conduit injury.
Figure 8.
After completion of the arteriotomy, the anastomosis of the left internal thoracic artery to the left anterior descending is constructed with a double-armed fine polypropylene suture. LAD = left anterior descending coronary artery; LITA = left internal thoracic artery.
Figure 9.
The circumflex artery is grafted next with the free right internal thoracic artery. To expose the lateral surface of the left ventricle, an apical suction cup is positioned on the apex of the left ventricle and suction is applied. The apex of the heart is retracted toward the middle of the right sternum. Care should be taken not to kink or bend the right ventricle during this positioning maneuver. The right heart may become compressed against the right sternum and right pericardium when retracting the heart to the right, and it is often necessary to create more space in the chest for the right heart. This is accomplished by incising the right pleura parallel to and along the entire length of the sternum and extending the pericardiotomy along the right side of the diaphragm posteriorly toward the inferior cava. The pericardiotomy is stopped just anterior to the phrenic nerve to avoid phrenic nerve injury. Additional space may be created for the right heart by removing the right-sided pericardial fat, placing towels under the right side of the sternal retractor to elevate the right side of the sternum, and dividing the muscular attachments of the diaphragm on the underside of the right sternum. LITA = left internal thoracic artery; LV = left ventricle; RITA = right internal thoracic artery.
Figure 10.
A suction stabilizer is used to stabilize the lateral circumflex. The stabilizer is attached to the sternal retractor and the prongs of the stabilizer are placed on either side of the coronary artery at the site of the planned anastomosis. A single proximal vessel loop is used to obtain hemostasis and fine sutures are placed on either side of the coronary artery in the epicardium and placed on tension to assist with visualization during construction of the anastomosis. LV = left ventricle.
Figure 11.
After completion of the arteriotomy, the anastomosis of the free right internal thoracic artery to lateral circumflex is constructed with a double-armed fine polypropylene suture. RITA = right internal thoracic artery.
Figure 12.
To expose the posterior descending artery, the apex of the heart is retracted superiorly toward the sternal notch. The suction stabilizer is attached to the sternal retractor and the prongs of the stabilizer are placed on either side of the posterior descending artery at the site of the planned anastomosis. A single proximal vessel loop is used to obtain hemostasis during construction of the distal anastomoses. It is placed around the posterior descending artery, just proximal to the location of the planned distal anastomosis. Fine sutures are placed on either side of the posterior descending artery in the epicardium and placed on tension to assist with visualization of the arteriotomy during construction of the gastroepiploic to posterior descending artery anastomosis.
The gastroepiploic artery is used as an in situ graft to bypass the posterior descending artery. In the abdomen, the gastroepiploic artery is positioned anterior to the stomach and left lobe of the liver and brought into the mediastinum through a cruciate incision in the diaphragm. An arteriotomy is made in the posterior descending artery, and the anastomosis of the gastroepiploic artery to the posterior descending artery is constructed with a double-armed fine polypropylene suture.
Figure 13.
The left internal thoracic artery has been used as an in situ graft to bypass the left anterior descending, the right internal thoracic artery as free graft to bypass the lateral circumflex, and the gastroepiploic as an in situ graft to bypass the posterior descending artery. The proximal anastomosis of the right internal thoracic artery graft has been constructed to the left internal thoracic artery in a “T” fashion. After completion of all bypass grafts, heparin is reversed with protamine and hemostasis is obtained. Chest tubes and pacing wires are placed, and the median sternotomy is closed. Aspirin is administered postoperatively. LITA = left internal thoracic artery; RITA = right internal thoracic artery.
Conclusions
Using these techniques of coronary artery exposure and stabilization, off-pump coronary revascularization can be performed safely and accurately in the majority of patients presenting for surgical revascularization. Whether off-pump revascularization lowers the risk of surgical revascularization has been a highly debated and controversial issue in coronary surgery during the last decade. Off-pump revascularization has the potential for lowering the risk of coronary surgery by eliminating cardiopulmonary bypass, and all arterial off-pump revascularization using in situ and composite grafts has the potential to further reduce risk by eliminating the need for aortic manipulation.
Although several early observational studies suggested lower hospital mortality and morbidity with off-pump revascularization, randomized studies and well-adjusted observational studies comparing the outcomes of off-pump to on-pump coronary surgery have challenged these findings.1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 These later studies found similar hospital mortality and major morbidity in patients undergoing off-pump or on-pump surgery. These studies did find less blood loss, need for transfusion, and myocardial enzyme release after off-pump surgery.5, 6, 7, 10 The randomized trials, however, contained relatively low-risk patients, and the risk of cardiopulmonary bypass would not be expected to be high in these patients. Because the risk of cardiopulmonary bypass increases with greater patient comorbidity, it would be expected that patients with more comorbidities, such as the elderly or those with ascending and aortic arch atherosclerosis, would derive benefit from off-pump surgery, whereas younger patients with few or no comorbidities would derive little or no benefit from off-pump revascularization. Observational studies comparing the outcomes of on-pump and off-pump surgery in high-risk patients support this conclusion.12, 13, 14
Midterm survival and freedom from reintervention have also been found to be similar after both on-pump and off-pump surgery.3 Although there have been conflicting reports as to whether bypass graft patency after off-pump surgery is as good as after on-pump surgery, angiographic studies from surgeons experienced with both on-pump and off-pump surgery have demonstrated similar graft patency with both revascularization techniques.9, 10
With these illustrated techniques, coronary artery bypass surgery can be performed off-pump in the majority of patients presenting for surgical revascularization. Clinical studies have demonstrated off-pump surgery to be at least as effective as on-pump surgery, with similar hospital mortality and morbidity, midterm survival, freedom from revascularization, and bypass graft patency. Off-pump revascularization should benefit most patients at greatest risk from cardiopulmonary bypass.
References
- Does off-pump coronary surgery reduce morbidity and mortality? . J Thorac Cardiovasc Surg . 2002;124(4):698–707
- Comparison of coronary bypass surgery with and without cardiopulmonary bypass in patients with multivessel disease . J Thorac Cardiovasc Surg . 2004;127(1):167–173
- Equivalent midterm outcomes after off-pump and on-pump coronary surgery . J Thorac Cardiovasc Surg . 2004;127(1):142–148
- A comparison of short- and long-term outcomes after off-pump and on-pump coronary artery bypass graft surgery with sternotomy . J Am Coll Cardiol . 2004;43(4):557–564
- Off-pump versus on-pump myocardial revascularization in low-risk patients with one or two vessel disease (perioperative results in a multicenter randomized controlled trial) . Ann Thorac Surg . 2004;77(2):569–573
- Off-pump versus on-pump coronary surgery (final results from a prospective randomized study PRAGUE-4) . Ann Thorac Surg . 2004;77(3):789–793
- Off-pump coronary artery bypass grafting provides complete revascularization with reduced myocardial injury, transfusion requirements, and length of stay (a prospective randomized comparison of two hundred unselected patients undergoing off-pump versus conventional coronary artery bypass grafting) . J Thorac Cardiovasc Surg . 2003;125(4):797–808
- . Off-pump coronary revascularization (current state of the art) . Semin Thorac Cardiovasc Surg . 2002;14(1):70–81
- Off-pump vs conventional coronary artery bypass grafting: early and 1-year graft patency, cost, and quality-of-life outcomes: a randomized trial . JAMA . 2004;291(15):1841–1849
- A randomized comparison of off-pump and on-pump multivessel coronary-artery bypass surgery . N Engl J Med . 2004;350(1):21–28
- A comparison of on-pump and off-pump coronary bypass surgery in low-risk patients . N Engl J Med . 2003;348(5):394–402
- Off-pump coronary artery bypass grafting reduces mortality and stroke in patients with atheromatous aortas (a case control study) . Circulation . 2003;108(suppl 1):II15–II20
- Coronary artery bypass in patients 80 years and over (is off-pump the operation of choice?) . Ann Thorac Surg . 2002;74(4):S1340–S1343
- . Off-pump coronary artery bypass grafting for elderly patients . Ann Thorac Surg . 2001;72(6):2013–2019
PII: S1522-2942(06)00057-2
doi:10.1053/j.optechstcvs.2006.06.002
© 2006 Elsevier Inc. All rights reserved.
Volume 11, Issue 2 , Pages 90-104, Summer 2006
