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© 2004 European Association of Cardio-Thoracic Surgery
Totally arterial off-pump vs. on-pump coronary revascularization: comparison of early outcomeClinic for Cardiovascular Surgery, Swiss Cardiovascular Center Bern, University Hospital, CH-3010 Bern, Switzerland
* Corresponding author. Tel.: +41-31-632-9268; fax: +41-31-632-2919 Received May 31, 2003; received in revised form November 3, 2003; accepted November 17, 2003
Our objective was to assess differences in early outcome after completely arterial myocardial revascularization with (on-pump coronary artery bypass grafting or ONCAB) or without cardiopulmonary bypass (off-pump coronary artery bypass grafting or OPCAB). Fifty-eight OPCAB and 91 ONCAB patients receiving exclusively arterial grafts were analyzed. OPCAB patients had more single-vessel  less triple-vessel  or left main disease  higher angina class  more unstable angina and previous percutanueous transluminal coronary angioplasty (PTCA;  ), but similar EuroScores  ONCAB was associated with longer operation time  and more anastomoses/patient  Internal thoracic artery (ITA) use was identical, whereas single left ITA use and left ITA jump anastomoses were more frequent in OPCAB. Radial artery (RA) use and RA jump anastomoses were more frequent in ONCAB. Complication rates were similar concerning mortality, arrhythmias, cerebro-vascular accidents (CVA), and renal failure with shorter ventilatory support and a trend towards less perioperative myocardial infarction (PMI)  and low output  and more respiratory complications  after OPCAB. Arterial OPCAB patients have less extensive CAD, but more severe symptoms. Early outcome is similar concerning mortality, arrhythmias, CVA, renal failure, or intensive care unit and hospital stay, but with shorter ventilatory support and a trend towards lower PMI and low output, and higher respiratory complication rates after OPCAB.
Key Words: Off-pump coronary artery bypass surgery; Cardiopulmonary bypass; Outcome; Arteries
Off-pump coronary artery bypass grafting (OPCAB) has been shown to produce excellent results [1,2]. Although arterial grafts provide superior long-term outcome compared to saphenous vein grafts (SVG) [3–5], many surgeons still prefer SVGs in addition to internal mammary artery grafts in OPCAB surgery. However, coronary artery bypass grafting (CABG) patients should not be deprived of these long-term benefits of arterial grafts because of the short-term advantages of off-pump procedures. Instead, both modalities should be combined to maximize their potential benefits. We therefore have used exclusively arterial grafts in a growing number of patients scheduled for OPCAB. However, short- and long-term efficacy and safety of arterial OPCAB are still poorly investigated. In order to analyze our early experience with exclusive use of arterial grafts in OPCAB procedures, we have compared it to patients undergoing exclusively arterial on-pump coronary artery bypass grafting (ONCAB) during the same period of time.
We analyzed demographic variables, technical details and perioperative results of 149 consecutive patients, undergoing coronary revascularization with exclusively arterial grafts between July 1999 and December 2001 (Table 1). They represent 17.1% (149/870) of CABG operations performed during the same period at our institution. Fifty-eight (40% of OPCAB procedures) were operated without cardiopulmonary bypass (CPB) (OPCAB; group A), and 91 (12.6% of ONCAB) were operated with CPB (ONCAB; group B). More patients had single-vessel disease , simultaneous severe stenosis of left anterior descending (LAD) and right coronary artery (RCA)  and less triple-vessel disease left main disease  and severe stenosis of the circumflex artery in group A than B. Mean angina class was higher more patients had unstable angina (NYHA class 4;  or had undergone previous percutaneous transluminal coronary angioplasty (PTCA) and stenting in group A than B. However, EuroScore was not different between the groups.
OPCAB is indicated in patients with an expected high risk for additional morbidity attributed to CPB, i.e. cerebral or renal co-morbidity, in those with severe aortic calcification and whenever thought to be technically feasible. Contra-indications are target vessels <1.5 mm, calcified or running intramyocardialy, and severe cardiomegaly (left ventricular end diastolic dimension >70 mm). Arterial grafts are especially advocated in patients under 70 years of age. The left internal thoracic artery (LITA) is used to revascularize the LAD and the right internal thoracic artery (RITA) for the RCA or its branches. In diabetic patients, bilateral internal thoracic artery (ITA) use is avoided. The radial artery (RA) is the second conduit in addition to the ITA mainly to revascularize the posterior left ventricular wall. Both LITA and RITA are harvested as pedicled grafts and sprayed with papaverine solution (10% papaverine diluted in 20 ml of NaCl). The RA is harvested via longitudinal skin incision using a no-touch technique, and stored in a blood-saline solution containing papaverine. With OPCAB coronary exposure is done by gradual cardiac luxation with one deep pericardial retracting suture. Target vessels are immobilized with the Octopus tissue stabilization systems (Medtronic Inc., Minneapolis, MN, USA) and proximally snared with a 4.0 polypropylene, while distal snaring is avoided. An intracoronary (IC) shunt (ICS Medtronic Inc., Minneapolis, MN, USA) is usually used to prevent myocardial ischemia. With ONCAB myocardial preservation is done with antegrade or retrograde cold blood cardioplegia, repeated every 20 min and given warm before declamping. All anastomoses are performed in standard fashion using 7.0 or 8.0 polypropylene running sutures. To prevent graft spasms, hypotensive episodes are avoided and most patients are put on oral nitrates postoperatively for at least 6–8 weeks. No routine control angiography is done postoperatively. 2.1. Statistics Data are expressed as mean value±SD. Percentages are given wherever appropriate. Statistical analysis was performed using Statview 5.0.1 for Windows (SAS Institute Inc., Cary, NC, USA). For univariate analysis, the Mann–Whitney U-test for continuous data and the Fisher's exact test for nominal data were used. A P-value of <0.05 was determined statistically significant.
Mean operation time was longer in group B than A (182.5±38 vs. 147±56 min;  Table 2). However, total operation time in relation to the number of distal anastomosis made was significantly longer in group A than B (79.5±32.9 vs. 61.7±21.4 min; ). This relation remains the same, when excluding patients with single-vessel disease (70.2±18.5 min vs. 60.8±20 min;  ). IC shunts were used for 46 anastomoses (39.3%), mostly of the LAD (26/54 anastomoses; 49%). Although the number of anastomoses performed was higher in group B than A (3.2±1 vs. 2±0.9; ), which remained unchanged when excluding single-vessel disease (3.3±1 vs. 2.5±0.7; ), the proportion of patients with incomplete revascularization was similar in both groups [17 (group A) vs. 11% (group B);  ]. The proportional use of LITA or RITA was the same in both groups, whereas single LITA use (25.9 vs. 1%; ) and LITA jump anastomoses (10.3 vs. 7.7%; ) were more frequent in group A than B. RA use (89 vs. 46.6%; ) and jump anastomoses (57.1 vs. 12.1%; ) were more frequent in group B than A. OPCAB patients were warmer than ONCAB patients (34.8±0.7 vs. 32.8±0.7 °C; ).
Overall, postoperative complications were not different between the groups (Table 3) concerning mortality, arrhythmias, cerebro-vascular accidents (CVAs), renal failure, wound infections and revisions. All CVAs were transient and no residual impairments present at discharge. However, maximal postoperative troponin-I as well as maximal creatine kinase (CK) and CK–MB levels were higher in group B than A (  ). Nitrates were used in all patients of group B and in 67.3% of group A (). There was a trend towards lower PMI (1.7 vs. 7.7%;  ) and low output rates (1.7 vs. 8.8%;  ) in group A than B. Despite a trend towards more frequent respiratory complications, i.e. pneumonia, acute respiratory distress syndrome or respiratory insufficiency (10.3 vs. 2.2%;  ), ventilatory support was shorter in group A than B (8.8±11.8 vs. 15.6±9.4 h; ), whereas intensive care unit (ICU) and hospital stay were similar in both groups.
Venous in addition to ITA grafts are still preferred by many surgeons in the setting of OPCAB revascularization, despite excellent mid-term patency rates [6] of arterial grafts after OPCAB and associated beneficial long-term outcome [5,7]. At present, there are only very few comparative data concerning early results [8,9] and none on long-term outcome after completely arterial ONCAB vs. OPCAB. Our retrospective investigation revealed several important findings with regard to early outcome after exclusively arterial CABG. First, patients selected for arterial OPCAB have several distinct baseline characteristics, making them a unique patient population. Second, exclusively arterial OPCAB is feasible and safe. Third, arterial just like conventional OPCAB is associated with less myocardial injury, which may translate into clinical benefits of less myocardial infarction and low output rates. Fourth, arterial just like conventional OPCAB may not further decrease stroke, renal failure or arrhythmia rates, but may shorten ventilation times, ICU and length of hospital stay. The careful selection of arterial OPCAB patients translates into expected differences in baseline characteristics with less extensive CAD. This resulted in less RA use, fewer anastomoses performed per patient and consecutively in a shorter operation time. However, OPCAB patients presented with more simultaneous severe stenosis of LAD and RCA, more severe symptoms of CAD, and more often previous PTCA and stenting than ONCAB patients. The significantly less number of anastomoses per patient in OPCAB than ONCAB did not entail a larger proportion of incomplete revascularized patients, since criteria applied for graftability of target vessels were identical for both groups. OPCAB and the exquisite use of arterial grafts, therefore, did not compromise the goal of complete revascularization. Other series have also reported less number of anastomoses performed in OPCAB vs. ONCAB [9–11] with numbers comparable to ours (1.7–2.5) in exclusively arterial [6,9], or higher [10,11] (3.0–4.5) and shorter operation times [8,9]. Mortality rates remained low in our series (0%, 3.3%), which is consistent with contemporary completely arterial OPCAB (0–3.2%) or ONCAB (0–4.5%) series [3,9,11,12]. There was a trend towards a decreased PMI rate (1.7%) after arterial OPCAB comparing favorably with other published series (0–2.2%) of exclusively arterial [9,11] or mixed OPCAB surgery [1]. The relatively high PMI rate (7.7%) after ONCAB compared to others (0.8–5%) [3,9] may have increased this trend further. Most authors did not find a significant difference between OPCAB and ONCAB either [1,9,11]. We could not attribute any of these infarctions to arterial spasms or technical difficulties, but rather to incomplete myocardial protection with greater myocardial injury demonstrated by the significantly higher peak levels of cardiac enzymes after ONCAB in our and other series [8]. Together with more extensive surgery, this may eventually translate into a trend towards more frequent PMI and low output in our patients after ONCAB compared to OPCAB. The higher use of RA grafts in the ONCAB group may not have an additional adverse effect, since it has been shown to be protective against early mortality and morbidity and have even less PMI than with the use of vein grafts [5]. The higher respiratory complication rate after OPCAB vs. ONCAB is surprising and with similar preoperative risk factors (smoking, obesity, diabetes) in both groups its reason remains elusive. It may be associated with the aggressive fluid loading during surgery, which may promote ‘wet lungs’ with consecutive activation of bronchial secretion and increased risk for airway infections in the early postoperative period. Nevertheless, ventilatory support was significantly shorter after OPCAB than ONCAB, but without influencing the length of ICU stay. Others as well have found shorter ventilatory support times [10,11], but also shorter ICU stay [6,10–12]. Although reduction of CVA [13,14], atrial fibrillation [11,12], renal failure [2,11], transfusion requirements [8] or length of stay [6,10–12] have been demonstrated in OPCAB vs. ONCAB, we and others [1,8,9,15] could not corroborate these findings with similar rates in both groups. Avoidance of CPB did therefore not translate into a clinical benefit for arterial OPCAB patients. But despite the more severe clinical presentation, OPCAB patients had a comparable overall early outcome to ONCAB patients. Others as well have found similar outcomes comparing on- and off-pump procedures despite the more severe clinical presentation in OPCAB patients [9], whereas others reported even better outcomes after OPCAB procedures [12] and even high-risk patients seem not to be negatively affected by the use of arterial grafts [11]. The power of the present study is limited by its non-randomized design. Our control population, the ONCAB group, is therefore not matched and the present differences in baseline characteristics, which are the consequences of selection bias, may potentially have influenced the outcome measures. Patients with less extensive CAD are more likely to be selected for OPCAB, whereas those with triple-vessel and left main disease are more likely to have ONCAB. However, the groups are not different concerning perioperative risk factors for mortality, as demonstrated by similar mean EuroScores. Despite these imperfections, our findings appear to be generally applicable, since they are in close concordance with those of a recently published controlled randomized [2] and case-matched trial [8]. Furthermore, our study truly reflects patient selection and early results obtainable with complete arterial CABG at a teaching institution. It also allows analyzing the results in the very specific subgroup of completely arterial OPCAB patients, whose outcome has not been fully assessed by now. We could be criticized for performing complete arterial OPCAB procedures at this stage of limited knowledge. However, OPCAB has emerged as a valuable alternative in CABG surgery, while there is increasing concern of impaired long-term graft patency with the use of vein grafts, also in OPCAB surgery [7]. Extrapolating the long-term benefits associated with arterial grafts in ONCAB to OPCAB procedures may therefore be a reasonable approach to improve the overall benefits of these procedures from a theoretical standpoint. Whether it holds true in practice however, remains to be further investigated. In conclusion, patients selected for totally arterial OPCAB present with less extensive CAD, but with more severe symptoms. Early outcome after arterial OPCAB is similar to ONCAB revascularization concerning mortality, arrhythmias, CVA, renal failure, or ICU and hospital stay, but with shorter ventilatory support and a trend towards lower myocardial infarction and low output but higher respiratory complication rates.
Definitions The following definitions were given:
ICVTS on-line discussion Author: Dr. Hotoshi Hirose, Juntendo University Hospital, Cardiovascular Surgery, 2300 Overlook Rd #312, Cleveland, OH 44106, USA Date: 10-Dec-2003 Message: This paper provides contradictory data. According to the authors, the postoperative ventilation time was significantly shorter in the off-pump bypass group than in the on-pump group; however, the off-pump group had more frequent respiratory complications than the on-pump group. I would like the author to clarify these "respiratory complications". What kind of respiratory complications were actually observed in the off-pump group? For example, pneumonia and adult respiratory distress syndrome are completely different disease process; however, the authors analyzed both conditions in one category. Author: Prof. Yahia Balbaa, Cairo University, Cardiothoracic Surgery, 4 El Zafer Street, El Haram, Cairo 12111, Egypt Date: 18-Dec-2003 Message: I am very interested to know the rate of conversion from off-pump to on-pump and the reasons for conversion. When cases were converted intra-operatively were these results discarded or added to the on-pump group? doi:10.1016/S1569-9293(03)00271-8
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Abstract
1. Introduction