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Ann Thorac Surg 2002;74:S1353-S1357
© 2002 The Society of Thoracic Surgeons

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Supplement: Cardiothoracic Techniques and Technologies

Off-pump multivessel coronary artery surgery in high-risk patients

^a Department of Cardiovascular Surgery, Escorts Heart Institute and Research Centre, New Delhi, India

* Address reprint requests to Dr Meharwal, Senior Consultant Cardiac Surgeon, Escorts Heart Institute and Research Centre, Okhla Road, New Delhi 110, India.
e-mail: meharwal{at}hotmail.com

Presented at the Eighth Annual Cardiothoracic Techniques and Technologies Meeting 2002, Miami Beach, FL, Jan 23–26, 2002.

	Abstract

Top Abstract Introduction Material and methods Results Comment References

 
BACKGROUND: Coronary artery bypass surgery on cardiopulmonary bypass is associated with significant morbidity and mortality, which may be more marked in high-risk patients. We evaluated our results of off-pump coronary artery bypass (OPCAB) in high-risk patients with multivessel coronary artery disease and compared them with results in similar patients who underwent operation on cardiopulmonary bypass.

METHODS: A total of 1,075 patients who underwent OPCAB between October 1996 and June 2001 and who had one or more of the following risk factors were included in the study: poor left ventricular function (EF 30%), advanced age (>70 years), left main stenosis, acute myocardial infarction, and redo coronary artery surgery. These patients were compared with 2,312 similar patients who underwent coronary artery bypass grafting on cardiopulmonary bypass during the same period. Preoperative risk factors, intraoperative variables, and postoperative results were analyzed and compared between two groups.

RESULTS: The average number of grafts was 3.0 ± 0.4 and 3.2 ± 0.3 in the off-pump (OPCAB) and on-pump (CCAB) groups, respectively. Hospital mortality was 3.2% and 4.5% in OPCAB and CCAB groups respectively (p = 0.109). Perioperative myocardial infarction, requirement of inotropic agents, stroke, and renal dysfunction were comparable in two groups. Intubation time (19 ± 5 vs 24 ± 6 hours, p < 0.001), mean blood loss (362 ± 53 vs 580 ± 66 mL, p < 0.001), atrial fibrillation (14.3 vs 19.7%, p < 0.001), and prolonged ventilation (4.6 vs 7.6%, p = 0.002) were less in OPCAB group. Intensive care unit stay (20 ± 8 hours) and hospital stay (6 ± 3 days) were significantly less in the OPCAB group (p < 0.001).

CONCLUSIONS: Off-pump coronary artery surgery can be safely performed in high-risk patients with multivessel coronary artery disease. Operative mortality is comparable to that associated with on-pump surgery, and avoidance of cardiopulmonary bypass is associated with reduced postoperative morbidity in these patients.

	Introduction

Top Abstract Introduction Material and methods Results Comment References

 
Previous reports have demonstrated that advanced age, reoperative coronary artery bypass grafting (CABG), and severe left ventricular dysfunction are the most important independent predictors of operative mortality after CABG [1, 2]. Cardiopulmonary bypass (CPB) is associated with diffuse systemic inflammatory responses during and after cardiac surgery [3, 4] and may contribute to the morbidity associated with CABG [5]. Off-pump coronary artery bypass grafting (OPCAB) has emerged as an alternative technique allowing coronary revascularization without the risk associated with CPB [6]. The OPCAB approach has been shown to reduce the overall systemic inflammatory response, including cytokine-mediated response [7, 8]. It also avoids physiologic derangement to the heart caused by cardioplegic arrest as shown by reduced troponin T release [7, 9]. Recent development of various tools and techniques, including several stabilizers and intracoronary shunts, have made OPCAB a safe procedure that is now being used for treating multivessel coronary artery disease, even in patients who are at high risk.

In this study, we analyzed our results of OPCAB in high-risk patients and compared them with results of CABG on-pump (ie, conventional CABG) in a similar group of patients.

	Material and methods

Top Abstract Introduction Material and methods Results Comment References

 
Data were prospectively collected on patients who were undergoing off-pump coronary artery bypass surgery (OPCAB group) and who had one or more of the following risks factors: age greater than 70 years, poor left ventricular ejection fraction (EF 30%), significant left main coronary artery stenosis (70%), redo surgery, and acute myocardial infarction operated within 48 hours. The decision for a patient to undergo operation on pump or off pump was made by the operating surgeon. All surgeons in the department perform off-pump and on-pump procedures with nearly equal distribution. Preoperative risk factors, intraoperative variables, and postoperative results were analyzed and compared with those for patients with similar risk factors who were undergoing conventional coronary artery bypass (ie, CABG on cardiopulmonary bypass; CCAB group) during the same period.

Anesthetic and anticoagulation protocol
Patients were premedicated using morphine (0.1 mg/kg) and lorazepam (2 to 4 mg). Induction of anesthesia was achieved with midazolam (15 to 20 µg/kg) and fentanyl (10 to 100 µg/kg). Muscle relaxation was achieved with vacuronium bromide (0.10 to 15 mg/kg). Anesthesia was maintained with oxygen, air, and incremental doses of midazolam and fentanyl. Heparin was injected in a dose of 2 mg/kg in patients who underwent operation without CPB and 3 mg/kg in patients with CPB. Activated clotting time was measured initially and then every 30 minutes; it was maintained for more than 300 seconds in patients who underwent surgery off pump and more than 400 seconds in those who had their surgery on pump. Protamine sulfate was used in 1:1 ratio to reverse the heparin effect after the procedure.

A femoral arterial line was used for insertion of an intraaortic balloon pump if a patient became unstable during induction of anesthesia or at a later stage before revascularization

Hemodynamic monitoring
Hemodynamic monitoring comprised of six-channel electrocardiography with ST-segment trend analysis, radial arterial pressure, and pulmonary artery measurements. Recorded variables were mean arterial pressure, central venous pressure, mean pulmonary pressure, pulmonary capillary wedge pressure, cardiac index, stroke volume, and systemic vascular resistance. Oxygen saturation was continuously monitored with a pulse oximeter. Arterial blood gases and activated clotting time ACT were monitored every 30 minutes. Intraoperative transesophageal echocardiographic monitoring was done using a multiplane transducer and Sonos 5500 imaging system (Hewlett Packard, Andover, MA). Variables monitored included: regional wall motion abnormalities, changes in global and regional LV function, LV filling, right atrial filling, mitral regurgitation, and right ventricular outflow tract obstruction.

Surgical technique for off-pump coronary artery bypass surgery
All patients underwent operation through a median sternotomy. The left internal mammary artery (LIMA) was harvested by standard technique using hemoclips. The other conduits (saphenous veins and radial artery) were harvested simultaneously. Octopus 2, Octopus 2+, and Octopus 3 (Octopus tissue stabilization system, Medtronic Inc, Minneapolis, MN) or CTS MIDCAB access platform and stabilizer (Cardiothoracic Systems, Cupertino, CA) were used to stabilize the target coronary vessel. Intracoronary shunts (Baxter AnastaFLO Intravascular shunt, Irvine, CA) were used for most of the anastomosis.

In most cases, the left anterior descending coronary artery was the first coronary artery to be grafted in most cases. The right coronary artery was normally the second artery, which was grafted. The vessels on the lateral and posterior wall were grafted last. However, the sequence of grafting was individualized for a particular patient, depending on the severity of the lesions in different coronary arteries and patient’s hemodynamics. Both the left anterior descending and right coronary arteries could be grafted without much displacement of the heart. For exposure of the circumflex vessels, three pericardial traction sutures were used to pull the heart vertically. The right pleura was opened wide and a vertical pericardiotomy was performed to herniate the heart to the right chest under the sternum. Other maneuvers such as the Trendlenberg position and tilting the table were performed as required. Inotropic agents were used as and when necessary during surgery. The distal anastomosis was performed using 7-0 or 8-0 Prolene (Du Pont Pharmaceuticals, Wilmington, DE) suture.

Proximal anastomosis was performed using standard techniques. The aorta was palpated before applying partial occlusion clamp for proximal anastomosis. Intraoperative transesophageal echocardiography was used to assess arteriosclerosis of the aorta. Recently we have also started using epi-aortic scanning to assess the proximal aorta. If there was any evidence of significant aortic arteriosclerosis, clamping of the aorta was avoided and proximal anastomosis was performed to the LIMA pedicle. The proximal anastomosis was performed using 6-0 Prolene suture.

Surgical technique for on-pump coronary artery bypass surgery
Conventional coronary artery bypass procedures were performed using standard CPB, which was established using ascending aortic and two-stage venous cannulation. The LIMA, radial artery, and saphenous veins were harvested by standard techniques. The patient was not actively cooled but temperature was allowed to drift. Antegrade or combination of antegrade and retrograde warm blood cardioplegia was used for myocardial protection. Cardioplegia was repeated after every distal anastomosis. A total of 76 patients (3.3%) underwent operation on CPB without arresting the heart (ie, with an empty beating heart). Hemodynamic monitoring was performed using a Swan-Ganz catheter (Edwards Lifesciences LLC, Irvine, CA) and transesophageal echocardiography as in patients undergoing operation without CPB.

Study definitions
Perioperative MI was defined as development of new Q waves on postoperative electrocardiography or loss of R wave progression, new left bundle branch block, or new ST and T wave changes in association with an increase in creatine kinase (CK) level of more than 40 U/L or CK-MB/CK ratio of more than 5%. Blood loss was defined as total chest tube drainage until chest tubes were removed. Prolonged ventilation was defined as ventilation for more than 48 hours. Mediastinisis was defined as mediastinal collection with positive culture. Acute renal failure was defined as requirement of peritoneal or hemodialysis. Total operative time was defined as time from skin incision to closure of skin.

Urgent surgery was defined as surgery within 24 hours of angiography. Surgery was considered as emergency surgery when the patient was shifted directly to the operating theater from the catheterization laboratory or the surgery was required within a few hours of admission or of performing angiography.

Statistical analysis
Data are reported as mean ± SD. The ² and Fisher’s exact tests were used to compare categorical variables. Unpaired Student’s t test was used to compare intergroup means. Intensive care unit and hospital stay are presented as medians, with the Wilcoxon test used for comparing the data in two groups. A p value of less than 0.05 was accepted as significant. Variables that were not normally distributed were compared using the Mann-Whitney test.

	Results

Top Abstract Introduction Material and methods Results Comment References

 
Between October 1996 and June 2001, a total of 11,591 patients underwent isolated CABG at our institute. Out of these, 3,387 patients had one or more of the risk factors mentioned earlier. Of these patients in high-risk groups, a total of 1,075 underwent operation without CPB and 2,312 with CPB. The preoperative variables of the patients are shown in Table 1. Patients in the OPCAB group were significantly older than those in the CCAB group, and there were more women in the OPCAB group. Incidence of left main stenosis was greater in the CCAB than in the OPCAB group. The other risk factors were comparable in two groups except that there were more redo operations and more patients with aortic arteriosclerosis in the OPCAB group. The mean Parsonnet score was higher in the OPCAB group.

	Comment

Top Abstract Introduction Material and methods Results Comment References

In our study, the mortality of OPCAB was comparable to that of CCAB patients, although there were more elderly patients in the OPCAB group and there were more redo operations in this group. The mean Parsonnet score was also higher in the OPCAB than in the CCAB group. When compared between different subgroups, the mortality was not statistically significantly different.

Perioperative morbidity and mortality rates rise with increasing age in patients undergoing CABG [14]. The OPCAB approach has been shown to reduce perioperative complications and resource use in elderly patients [13]. The incidence of postoperative complications was less in the OPCAB than in the CCAB group in our study also. The stroke rate in our study was comparable in the two groups, though there were more elderly patients in the OPCAB than in the CCAB group, and more patients in the OPCAB group (12.8%) had arteriosclerosis of the aorta than those in the CCAB group. Ricci and colleagues [15] have also shown reduced incidence of stroke in octogenarians undergoing OPCAB. A possible mechanism may be the significantly higher rate of arteriosclerosis of the ascending aorta in octogenarians, which may potentiate migration of atheromatous microemboli to the brain during aortic cannulation and result in neurologic injury after on-pump CABG.

Patients with left main stenosis have been considered to be a relative contraindication to OPCAB surgery. However, with the development of exposure and stabilization techniques and the introduction of intracoronary shunts, even patients with critical left main disease can undergo off-pump surgery with good results, as recently reported by us [16] and by Yeatman and colleagues [17].

Other groups of patients who are at high risk with regard to surgery are those with severely impaired LV function. Most of these patients have a combination of risk factors, and expected mortality may reach 10% or higher [18, 19]. In our study, mortality in patients with poor LV function in the OPCAB group was comparable to that in the CCAB group. Many studies [12, 20] have reported excellent results for CABG on the beating heart in this group of patients. The relatively low mortality and morbidity observed after off-pump surgery in this group of patients may be explained by the favorable effect of the beating heart on the blood supply to the subendocardium [21], the reportedly better preservation of interventricular septal contractility after OPCAB [5, 22], and the avoidance of damaging effects of CPB and aortic crossclamping.

Exposure and stabilization of the vessels on the posterior and lateral walls present an occasional challenge in these patients, especially in the presence of significant cardiomegaly. Deep pericardial sutures, deep vertical right pericardiotomy, and extensive right pleurotomy help in maintaining hemodynamic stability during anastomosis on these vessels in these patients.

Redo CABG has been reported to be associated with relatively higher mortality and morbidity, and long CPB time has been identified as the most powerful independent predictor of mortality after reoperative CABG [23]. In this regard, avoidance of CPB may be considered a valuable alternative in these patients. The mortality of redo surgery in our study was not significantly different from that in the CCAB group.

Emergency CABG in patients with acute MI has poor results because the ischemic myocardium cannot endure the side effects of CPB and cardiac arrest; several authors have reported a mortality of 20% to 30% in patients undergoing conventional CABG with CPB [24]. The OPCAB approach may be a viable alternative in these patients [25]. During off-pump coronary revascularization in these patients, myocardial perfusion starts as soon as first distal anastomosis has been completed. This helps to stabilize the patient, and the other anastomosis can be performed in a relatively stable patient. We did not find significant difference in mortality in the OPCAB and CCAB groups.

In conclusion, off-pump coronary artery bypass is a safe alternative to conventional CABG in high-risk patients with multivessel coronary artery disease. This technique significantly reduces postoperative morbidity in these patients. However, prospective randomized studies with long-term results comparing these two techniques are required.

	References

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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): Zile Singh Meharwal Yugal K. Mishra Sandeep Singh Naresh Trehan Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Meharwal, Z. S. Articles by Trehan, N. Search for Related Content PubMed PubMed Citation Articles by Meharwal, Z. S. Articles by Trehan, N.