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© 2003 European Association of Cardio-Thoracic Surgery
A review of 507 off-pump coronary bypass patients: a single center experienceDepartment of Thoracic and Cardiovascular Surgery, Johannes Gutenberg University Mainz, Langenbeckstr. 1, D-55131 Mainz, Germany
* Corresponding author. Tel.: +49-6131-172106; fax: +49-6131-470193 Received October 27, 2002; received in revised form January 29, 2003; accepted February 10, 2003
This retrospective study evaluates perioperative results of ‘Off-pump‘ coronary artery bypass surgery (OPCAB) experience in a single center. Five hundred and seven patients were operated (median sternotomy) from 1998 to 2002 using OPCAB. Patient data were registered and risk prediction calculated using the full logistic version of EuroSCORE. Overall, 1091 distal anastomoses were performed and only five (1%) patients required conversion to cardiopulmonary bypass. The predicted mortality was 3.8±4.5%, the observed mortality was 2.37%. OPCAB technique has become a standard approach in our department with low mortality and morbidity rates even in treatment of multivessel disease or high-risk patients.
Key Words: Off-pump; Coronary artery bypass surgery
‘Off-pump’ coronary artery bypass surgery (OPCAB) is a relatively new operation technique, but has been rapidly established in many cardiac centers[1–3]. Although conventional bypass surgery with cardiopulmonary bypass (CPB) has been experienced as safe and effective, a number of disadvantages have been associated with this approach [4]. CPB may induces a whole-body inflammatory response, full heparinization is required and cannulation and cross-clamping of the ascending aorta may cause atheromatous makroemboli [5]. Expansion of multiple vessel OPCAB has been limited by difficulties due to adequate exposure of the local wall and hemodynamic instability [6]. Different devices had been developed to enable positioning of the heart in a simple way while preserving hemodynamic stability [2,7]. In this study, we performed OPCAB surgery using a vacuum assisted heart manipulator in combination with a rigid shaft, mechanical stabilizator [7]. The purpose of this single center report was to analyze the OPCAB experience. We present demographics, operative details and early outcomes (1 month).
2.1. Patient selection Five hundred and seven consecutive patients underwent OPCAB from February 1998 to July 2002 under the supervision of a single surgeon (U.H., 475 cases). The criteria for off-pump surgery in our institution have changed over the last 4 years because we gained more experience in OPCAB surgery. At present, contraindications for off-pump surgery are diffusely diseased small (<1.5 mm) vessels, oversized hearts needing posterior revascularization and emergency cases with evolving infarction. This protocol was discussed and approved by the department. Informed consent was obtained from every patient. 2.2. Management of preoperative and postoperative medication Preoperative medications with nitrates, ß-blockers, antihypertensives, ACE inhibitors and diuretics, were given until the day of surgery. On the first postoperative day, ß-blockers and antihypertensive drugs were restarted. ACE-inhibitors were applicated directly upon arrival at the intensive care unit. Calcium channel blockers were routinely given during the operation. Patients were maintained on daily aspirin postoperatively.2.3. Anesthetic technique A pulmonary catheter was inserted in all patients to monitor left-sided pressures and the cardiac output. Propofol infusion (3 mg/kg per h) was combined with sufentanil infusion (1 µg/kg per h). Heparin was given at a dose of 150 IU/kg, and activated clotting time (ACT) was checked to maintain a level of 250 s. After completion of all anastomoses, protamin was given 1:1 and the effect was checked by determination of the ACT. Aprotinin was infused (500,000 IE/h) during the operation (we used Aprotinin during the last 16 operations). The patient was placed on a warming mat (filled with water) during the operation and in addition covered with a specially designed warming trouser suit to keep the patients core temperature between 35 and 37 °C.2.4. Operative technique The method of exposure and stabilization to perform the anastomoses has undergone considerable evolution in the last 4 years. During the first 2 years we used deeply placed pericardial sutures to facilitate grafting of the posterolateral wall in combination with a vacuum stabilizator. In addition to this, we performed a right vertical pericadiotomy down to the phrenic nerve to provide space for the right ventricle during the verticalization of the heart in order to improve the hemodynamics during grafting of the posterolateral wall vessels. Furthermore, the heart rate was reduced with beta blockade, and difficult stitches were placed after administration of adenosine to arrest the heart. Snaring of the coronary artery was initially achieved by a simple ligature of 4-0 monofilament suture that was later replaced by soft silicon loops.We used a vacuum assisted heart manipulator (Xpose, Guidant Corp., Cupertino) and a mechanical stabilizator (Ultima, Guidant Corp., Cupertino). The target vessel was exposed and snared at the proximal site of the anastomoses with a soft silicon loop. Routinely coronary shunts (axius coronary shunts, Guidant Corp., Cupertino) were inserted into the artery whenever possible. The anastomoses were performed with a 7-0 prolene suture. To reduce the use of blood products, a cell saver was installed in all patients with more than one distal anastomosis. In case of bradycardia, atrial pacing was established. The proximal anastomoses were carried out with a 6-0 prolene suture under a partial occlusion clamp. Following the principle of functional revascularization, the anterolateral region of the myocardium was revascularized first with the left internal mammary artery. 2.5. Postoperative management At the intensive care unit pressure control ventilation was established, FIO2 and respiratory rate were adjusted according to the routine blood gas analysis. Extubation was enforced when the following criteria were fulfilled: no bleeding, hemodynamic stability, normothermia. Red blood cells were replaced as soon as the values of hemoglobin were below 8.5 mg/dl. Fluid substitution with Ringers Lactate was given at a rate of 100–150 ml/h.2.6. Data collection Data were entered prospectively into a locally maintained database (Access, Microsoft) and were then analyzed retrospectively. The baseline characteristics (Table 1) were registered preoperatively, and a risk prediction was calculated using the full logistic version of the EuroSCORE. The following intraoperative data were compiled: number of distal anastomoses, type of graft, and switch from off-pump to cardiopulmonary bypass. Postoperatively, the following data were compiled: blood loss, use of blood products, intubation time, incidence of atrial fibrillation, renal failure, myocardial infarction, mortality within 30 days after surgery, deep sternum infection, and reoperation within 30 days after surgery. Myocardial infarction was defined according to the standards of the Bundesgeschäftsstelle der Bundesarbeitsgemeinschaft Qualitätssicherung Herzchirurgie (www.bqs-online.de).
Data are expressed as average±S.D.
A total of 507 patients underwent the OPCAB procedure between 1998 and 2002. The patients had an average age of 64.4±10.2 years, with a range from 32 to 87; 72.2% were males and 8.7% were having re-do heart surgery; 475 (93.7%) were in NYHA functional class III–IV, and four (0.8%) required emergent CABG; 350 (69.1%) patients had a left ventricular ejection fraction (EF) >50% and 128 (25.2%) had an EF ranging from 30 to 50%. Twenty-nine (5.7%) had a very bad left ventricular function with an EF<30%. Other demographics are listed in Table 1. An average of 2.2±0.9 bypass grafts were conducted per patient, and a total number of 1091 distal anastomoses were performed. One hundred and thirty two (26%) had single bypass, 197 (38.9%) double, 148 (29.2%) triple, and 30 (5.9%) quadruple or quintuple bypass. Multiple arterial grafts were exclusively used in 16 (3.2%) patients. The intraoperative data are summarized in Table 2. There was no concentration of cases with respect to the risk profile in any single year, but the percentage and total number of OPCAB cases steadily increased from year to year. Furthermore, the average number of grafts increased during the time of study. The risk profile was determined using the European system for cardiac operative risk evaluation (EuroSCORE). The predicted mortality was 3.8±4.5 % and the observed mortality was 2.4%. Four patients died as a result of sepsis, two of them were dialysis patients. One patient died from unnoticed esophageal hernia with compression of the heart by parts of the stomach and intestines 8 days after the operation. One patient had a porcelain aorta and was operated as an emergency case with preoperative myocardial infarction. This patient died due to heart failure. The other six patients died due to perioperative myocardial infarction and heart failure. Conversion was necessary in five cases (1%) and 12 patients (2.37%) were re-operated for bleeding or graft failure. Transfusion of blood products was necessary in 41%. New atrial fibrillation occurred in 35.9% of patients. Mechanical ventilation was required for more than 24 h in 10% of patients. Perioperative myocardial infarction was detected in 18 (3.5%) patients and no stroke with permanent deficit was noted. Interestingly, 45 (8.9%) re-do cases were operated with a predicted mortality of 8.9% and an observed mortality of 2.2%. The postoperative data are listed in Table 3.
This study showed our experience with off-pump coronary bypass grafting in a large group of patients treated at the Department of Cardiothoracic and Vascular Surgery, University Mainz, during the last 4 years. In summary, results with the presented concept using the off-pump technique for revascularization have yielded excellent clinical outcomes, with low rates of morbidity and mortality [1,8]. Direct feedback for quality control and technique improvement is a requirement for the adaptation of any new surgical technique and therefore we analyzed our OPCAB patients. The performance of the graft to coronary artery anastomosis is more difficult in the OPCAB procedure compared to the conventional on-pump procedure on an arrested heart. Successful myocardial revascularization on the beating heart should be performed with as much security as in on-pump cases. This is possible with excellent exposition and local motion reduction at the anastomosis site. A vacuum suction device in combination with a mechanical stabilizator allow OPCAB grafting of multiple vessels to be completed with minimal hemodynamic effect and improved exposure [7]. Prerequisite for successful off-pump is a high level of skill and expertise and an optimal and rapid communication between anesthetist and surgeon, especially using heart displacement exposing the inferior or lateral heart wall [6]. Patient selection and surgical experience are the two essential points for successful OPCAB. Relevant contraindications for OPCAB are in our opinion: (1) small vessels (<1.0 mm diameter) or intramyocardial target vessels; (2) cardiomegaly (cardiothoracic ratio >0.7) if it is necessary to expose the lateral or inferior wall; and (3) patients suffering from an acute myocardial infarction. Recent work has established that regional myocardial dysfunction may be related to the temporary occlusion of the target coronary vessel when this technique is used to perform the anastomosis [9]. Occlusion of the coronary artery results in a bloodless field but this could be also achieved by using an intracoronary shunt. These shunts maintain distal perfusion and allow unhurried construction of anastomoses in a blood-free operative field. Furthermore, the arteriotomy could be spread with a soft tensile force applied to the tether of the shunt. This simple method makes it possible to perform safe and precise anastomoses. As mentioned before, we changed our operation management to reduce the use of blood products. Using a cell saver and holding the patient temperature between 35 and 37 °C seems to be essential. Furthermore, we used aprotinin during the last 16 operations and this method strongly suggests that it is possible to reduce blood loss. An important factor that potentially influence morbidity and mortality is the operation method and the patient management during the operation. Especially the last factor has changed over the last 4 years in our institution showing the development of this method. Even the published studies are difficult to compare with each other because the inclusion criteria and outcome measures quoted across the studies were very heterogeneous. We used a standardized risk prediction system (EuroSCORE) to classify the patients in the OPCAB group, and thanks to this method it was possible to compare the predicted and the observed mortality [10]. Furthermore, we are able to analyze high risk patients in this study, e.g. re-do cases (45, 8.9%). These patients had a predicted mortality of 8.9% and only an observed mortality of 2.2%. A review of the current literature on OPCAB in high risk patients strongly implicates that OPCAB is the superior method with respect to mortality and morbidity [11–13]. Many studies analyze the average intensive care unit and hospital stay, but in our opinion, this is not a good parameter to prove how safe and the effective this relatively new method is [14]. Limitations of this study could be seen in its retrospective nature and in the fact that so far no angiographic re-evaluations have been performed. The latter will be subject of a separate study. However, the ultimate value of OPCAB procedures will depend on the evaluation of long-term bypass patency. Finally, to clarify the role of OPCAB in the repertoire of surgeons, it is necessary to initiate a well defined multicenter study to investigate a sufficient number of patients with highly standardized treatment. By rigid inclusion criteria, extensive evaluation and validation of clinically relevant outcomes and lengthy follow-up, it is possible to draw a definitive conclusion regarding the safety and efficacy of OPCAB [2]. However, studies made available recently, imply that off- pump bypass grafting is a competitive method compared to conventional bypass grafting.
ICVTS on-line discussion Author: Dumbor Ngaage, Cardiothoracic Surgeon, Yorkshire Heart Centre, Department of Cardiothoracic Surgery, Great George Street, Leeds LS1 3EX, UK Date: 03-Apr-2003 12:43 Message: This report corroborates many others on the feasibility, safety and efficacy of OPCAB in the surgical treatment of coronary artery disease. The impact of OPCAB is constantly and consistently growing. The authors report a good early outcome with this technique in a patient population with diverse surgical risks. OPCAB is proving to be suitable in most patients requiring revascularisation. One major criticism of OPCAB is the proclivity to incomplete myocardial revascularisation, which does not seem to be the case in this report since the number of diseased vessels match the number of grafts. I wish to raise some concerns with this report. In the methods, mention is made of the use adenosine to arrest the heart. It is not clear why it was necessary to arrest the heart in OPCAB, and whether this a viable technical option? There is substantial evidence in favour of OPCAB, over on-pump CABG for revascularisation of high surgical risk patients, including those with acute myocardial infarction. The recommendation of the authors that recent myocardial infarction be considered a contraindication for OPCAB is therefore not only surprising, but also deviating, more so as their study did not provide contradicting evidence. Author: Leo Bockeria, Bakoulev Center for Cardiovascular Surgery, 135 Roublevskoye shosse, Moscow 121552, Russian Federation Date: 10-Jun-2003 15:06 Message: Very good OPCAB results in surgical treatment of coronary artery disease. OPCAB procedures are more often performed in this patient population. The authors' experience shows that this is not a tribute to fashion, that these surgeries can be used routinely in most of the patients with low risk. Still there are questions to be solved. What are the indications to OPCAB? What is the patency rate of the anastomoses performed with OPCAB technique? To what extent does OPCAB permit the accomplishment of technically precise anastomoses? The authors do not propose to cover these questions, but they still persist. It is not clear however why the authors had to resort to cardiac arrest and respectively why did they use adenosin? OPCAB is a surgery on a beating heart, isn't it? It is hardly propable to consider multiple bypass grafting when an average of 2.2 anastomoses per patient are performed. Comprehension is required as to why 507 patients had 653 LAD shunts (Table 2). Unfortunately the authors have not presented arguments in favor of OPCAB as compared to conventional bypass grafting.
We thank Marion Baetz for help with preparing the manuscript and Michael Prokop for evaluating the full logistic version of the EuroSCORE. doi:10.1016/S1569-9293(03)00034-3
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Abstract
1. Introduction