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Eur J Cardiothorac Surg 2001;20:760-764
© 2001 Elsevier Science NL
Departments of Cardiology and of Cardiovascular Surgery of Lausanne University Hospital and of Sion Regional Hospital, Lausanne, Switzerland
Received 5 January 2001; received in revised form 18 April 2001; accepted 30 May 2001.
Corresponding author. Tel.: +41-21-3142318; fax: +41-21-3142278
e-mail: philippe.gersbach{at}chuv.hospvd.ch
| Abstract |
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0.05. Results: Groups were widely comparable. There were no in-hospital deaths nor permanent neurologic events. OPCAB patients received more anastomoses (mean 1.09/patient vs. 1.89/patient, P<0.001) during a shorter coronary occlusion period (26.1±8 vs. 16.6±4.5 min, P<0.001), whilst immediate extubation prevailed in MIDCABs (22/31 vs. 17/39, P<0.05). Significant complications occurred in seven MIDCABs vs. none in OPCABs (P<0.01). Other in-hospital parameters were similar. Controls at 3 months evidenced more residual discomfort among MIDCAB patients (14/30 vs. 7/39, P<0.05). Conclusions: Differences in early complication rates may be due to a learning effect. However, OPCAB allows us to implant more grafts and is more comfortable for both patient and surgeon. These advantages may well counterbalance the cosmetic benefits of MIDCAB procedures.
Key Words: Coronary bypass techniques Minimal invasive-thoracotomy Off-pump sternotomy Completeness of revascularization Early and late morbidity Residual discomfort
| 1. Introduction |
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| 2. Patients and methods |
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The clinical files of the first 70 CABG procedures performed at the beating heart under identical conditions by a single surgeon with more than 20 years of experience in coronary surgery (F.S.) were reviewed. Patients were divided into MIDCAB (n=31) and OPCAB (n=39) groups. General and cardiac condition 3 months postoperatively was assessed by a standardized phone interview of the patient and his home physician. To avoid a possible magnification of his condition by the patient in order to please his surgeon [4], this interview was performed by an independent cardiologist, who was not aware of the operative technique.
2.1. Operative technique
As a single major difference between groups, an epidural catheter was placed 24 h preoperatively in MIDCABs at the high thoracic level (Th 34) for perioperative analgesia (carbostesin/sufentanil).
Anesthetic induction was performed in both groups with short-acting hypnotics, opioids (Propofol/Sevoflurane/Remifentanil), and muscle relaxing agents (Atracrurium) in order to facilitate early extubation. The operating theater was warmed up to 26°C for preservation of temperature homeostasis. All patients received standard monitoring equipment (radial artery catheter, two surface ECG leads, pulse oximetry, end-tidal pCO2 and, in cases of poor left ventricular function, a SwanGanz thermodilution pulmonary artery catheter). The ventricular function was continuously monitored by transesophageal echography (Ving Med CFM 750, Horten, Norway) in order to detect possible segmental wall motion abnormalities indicative of limited myocardial ischemia [5]. CPB facilities were systematically kept in stand-by throughout the procedures.
In OPCABs a full-length standard sternotomy was routinely performed and the left internal mammary artery (LIMA) and occasionally the right internal mammary artery (RIMA) was harvested with its pedicle on its whole length, simultaneously with the long saphenous vein whenever necessary. For MIDCABs, external defibrillator paddles were fixed at the external surface of the chest. A small left anterior thoracotomy was placed in the fourth intercostal space and the LIMA mobilized under direct vision as high as possible. This maneuver was facilitated by the use of a specific chest retractor (CardioThoracic Systems Inc., Cupertino, CA, USA).
MIDCAB and OPCAB operations were basically performed in a similar way: after opening of the pericardium and short inspection, low dose (150 IU/kg of body weight) heparin was administered intravenously. Short-acting ß-blockers (esmolol) and/or calcium antagonists (Diltiazem) were used to control heart rate and to minimize myocardial contractility and oxygen consumption. Volume loading with infusions allowed us to optimize cardiac output during manipulations. Pericardial stay sutures [6] and laparotomy pads placed progressively behind the heart helped to expose the target vessels. Immobilization of the operative site was achieved by placing the blades of an epicardial stabilizer (CardioThoracic Systems Inc., Cupertino, CA, USA) perpendicular to the target vessel allowing, in ideal cases, full control of the native coronary blood flow. If necessary, exposure was optimized by epicardial stay sutures and occasionally by encircling 4.0 propylen sutures placed around a wide pad of surrounding tissue proximal and distal to the intended site of arteriotomy. Distal anastomoses were completed with a single 8.0 Prolen (Ethicon, Somerville, NJ, USA) running suture. In cases of multiple grafts, the most important diseased coronary artery (generally the LAD) was bypassed first. In OPCABs, additional vein grafts to the circumflex and right coronary systems were implanted on the ascending aorta using a partial occlusion clamp. In order to avoid or reduce aortic manipulations, sequential bypasses were performed as often as possible.
2.2. Statistical analysis
Continuous variables were reported as mean±SD. Differences between groups were assessed by the two-tailed chi-square test or Student's t-test for independent samples, and significance assumed for P-values less than 0.05.
| 3. Results |
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| 4. Discussion |
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The vogue of MIDCAB surgery has prompted the emergence of numerous instrumental and technical refinements that in turn improved OPCAB feasibility and safety. Despite these recent developments, beating heart surgery remains technically more demanding than conventional CABG [14]. An original recent survey on minimal invasive CABG by Shennib et al. [15] has demonstrated that 74% of the surgeons using these techniques feel somewhat uncomfortable, mostly because of difficulties in stabilizing the target vessel and concern with the quality of the anastomoses. Comparisons between MIDCAB and OPCAB techniques should, therefore, also take into account the exact influence of the learning process of each of these procedures on early patient mortality and morbidity.
In this respect, the basic conditions of this study (initial experience of a single surgeon using the same technical set-up, in a single institution and during a limited period of time) allows a fair comparison between the two approaches. Among the seven substantial perioperative complications identified exclusively in the MIDCAB group, three myocardial infarctions in the freshly grafted LAD area may be related to inexperience: in one case of deeply embedded LAD, the anastomosis had to be performed very distally on a small vessel of poor quality; in the remaining two cases, LIMA harvesting through a small thoracotomy incision had been described as difficult. This confirms the potential of thoracoscopic techniques for LIMA preparation in MIDCABs [16], particularly when considering that such a procedure can be completed within 20 min [11].
The longer LAD occlusion time in MIDCABs must be interpreted with circumspection. Conflicting results have been reported on the risk of subclinical myocardial injury during target vessel occlusion. Bonatti et al. [17] have registered an elevation of creatine kinase MB mass concentration indicative of myocardial suffering in 56% and of cardiac troponin I level in 44% of MIDCABs. Systematic TEE observations by Jurmann et al. [5] have also evidenced hypokinetic changes in regional wall motion during LAD occlusion in 26 out of 28 MIDCAB patients. Conversely, Pentillä et al. [18] measured no significant increase of troponin T and creatine kinase-MB mass after coronary revascularization at the beating heart in 12 patients. It has finally been hypothesized that the increased perioperative mortality rate observed in hypertensive patients undergoing OPCABs may be due to lesser tolerance of hypertrophic left ventricles to short ischemic periods [9]. In the present study, no relationship could be found between the early postoperative course, the need for inotropic support, and the duration of coronary ischemia.
The different number of bypasses performed in each group mostly reflects the extent and characteristics of the underlying coronary disease, since patients necessitating a single LAD bypass can be treated as well by MIDCAB as by OPCAB procedures, whereas OPCAB is preferred in graftable multivessel disease. Nevertheless, incomplete revascularization has long been recognized as a major cause of recurrence of angina [19]. In the experience of Tasdemir et al. [9] an ungrafted circumflex artery disease emerged as the second most important determinant of in-hospital death as well as a significant predictor of perioperative myocardial infarction and low cardiac output after OPCAB procedures. Moreover, a recent observational clinical study by the group from the Cleveland Foundation [20] has shown an over 30% decrease in long-term survival among patients with non-revascularized lesions outside the LAD system. Finally, the importance of bypassing high diagonal branches that are hardly accessible through a MIDCAB approach remains controversial. Data of the CASS study [21] still indicate that the risk of myocardial infarction in any part of the LAD system over a 3-year period is 2% for mild stenosis increasing up to 78% for stenosis of 5090%. Unless long-term efficiency of hybrid procedures has been proven, MIDCAB techniques should, therefore, be reserved for isolated LAD lesions.
The opinion that MIDCAB is associated with reduced postoperative pain cannot be sustained by the present study. On the contrary, even though not significant, more MIDCAB patients complained of persistent thoracic pain 3 months postoperatively; in two cases, the pain was considered disabling.
A slight reduction of early postoperative pain from the third postoperative day onward has actually been reported after MIDCABs [22]. However, it must be stressed that intercostal nerves can always be damaged by thoracotomy, resulting in more or less severe chronic pain. In the present study the residual pain mostly observed after MIDCABs may be related to excessive spreading of the ribs [11]. Resection of costal cartilages and systematic video assisted harvesting of the LIMA may be effective in lessening the incidence and intensity of this complication.
The two groups show no differences in ICU and hospital stay duration (8.6±2.1 days in OPCABs and 8.9±3.9 days for MIDCABs). Discharge was proposed at the fifth postoperative day for 34 patients without disabling co-morbidites or significant perioperative complications. Among these, 25 refused, mostly because of a feeling of insecurity and/or an inadequate social environment. It therefore appears that, in this series, hospital stay duration is influenced much more by local standards and confidence of patients, relatives, and referring physicians than by the surgical approach itself. The importance of these socio-cultural local factors has been highlighted by a recent study showing that in another environment even patients with conventional CPB procedures can be safely discharged on the first and second postoperative day [23].
In summary, MIDCAB procedures are technically more demanding than OPCABs. For this reason, sternotomy seems to be the best approach when beginning with off-pump techniques. Furthermore, OPCAB allows a more extensive coronary revascularization and is more comfortable for both the patient and the surgeon. In case of hemodynamic instability, OPCAB also allows immediate conversion to CPB technique. These advantages may well counterbalance the cosmetic benefits of MIDCAB procedures.
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