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© 2004 European Association of Cardio-Thoracic Surgery
Results after MIDCAB and OPCAB surgeries: problems and consequences of incomplete angiographic follow-up in the mid-term course
a Department of Cardiovascular Surgery, University Hospital Freiburg, Hugstetter Str. 55, 79106 Freiburg, Germany
* Corresponding author. Tel.: +49-761-270-2881; fax: +49-761-270-2368 Received October 28, 2003; received in revised form December 19, 2003; accepted January 9, 2004
OBJECTIVE: The aim of this study was to evaluate the mid-term course of all patients who had undergone minimally invasive coronary artery bypass grafting in our department between January 1996 and September 2001. The procedures were performed on the beating heart without the use of cardiopulmonary bypass. Either median sternotomy (60 patients) or anterolateral thoracotomy (29 patients) was used for access. Evaluation focused on perioperative complications, quality of life, clinical status, graft patency, survival and freedom from cardiac events. Special emphasis was put on the problems and consequences of incomplete angiographic follow-up. METHODS: Survival and postoperative cardiac events of all patients were evaluated. All surviving patients were invited for follow-up examination. Angiographic control was recommended to all patients. RESULTS: Survival after 30 days was 100%. Two patients (2%) suffered from perioperative myocardial infarction due to early graft failure, which required reoperation in standard technique in both cases. Mean follow-up period was 25 months. Mean NYHA class improved from preoperative 2.3 to current 1.6, and the mean CCS class from 2.1 to 0.8. Angiographic controls were performed in 46/89 patients. Fifty-three anastomoses were evaluated, 47 of which showed no occlusion (patency rate 89%). Forty-two anastomoses (79%) were free of significant stenosis. In 27 patients without symptoms we recommended angiography for control purposes and observed a patency rate of 97%. Nineteen patients had already undergone angiographic control due to clinical complaints prior to follow-up examination. That group's graft patency rate was 78%. Survival was 98% after 1 year and 94% after 3 years. Survival free of cardiac events (myocardial infarction, reoperation, percutaneous transluminal coronary angioplasty) was 86% in the first year and 80% after 3 years. CONCLUSIONS: The results concerning survival, freedom from events, and clinical status are encouraging. It was not possible to perform angiographic controls in all patients since some of them and their primary physicians could not be convinced of the necessity of this control in the absence of clinical complaints. This explains the negative bias in our results.
Key Words: Coronary artery bypass; Surgical procedures; Minimally invasive; Treatment outcome; Follow-up studies; Coronary angiography; Quality of life
For many years, the use of cardiopulmonary bypass (CPB) and median sternotomy was the standard procedure for coronary artery bypass grafting (CABG) [1]. An increasing number of reports on the disadvantages of extracorporeal circulation have led to a revival of beating heart CABG. The use of CPB is associated with a systemic inflammatory response and microembolism from plaques, platelet aggregates and air. These mechanisms may cause damage to multiple organs [2]. Evidence of late neurocognitive deficits after on-pump surgery has led to growing scepticism concerning the use of CPB [3]. In some patients with extremely calcified vessels, ascending aorta cannulation is only possible with a high risk of plaque embolism [4]. There is controversy as to whether minimally invasive procedures can achieve the same long-term benefit for the patient and an equal quality of the anastomoses as it has been reported for standard CABG [5]. The aim of this study was to evaluate the mid-term course of all patients who had undergone minimally invasive CABG in our department between January 1996 and September 2001. Either off-pump coronary artery bypass grafting (OPCAB) using median sternotomy or minimally invasive direct coronary artery bypass grafting (MIDCAB) using anterolateral thoracotomy was performed. Evaluation focused on perioperative complications, quality of life, clinical status, graft patency, survival, and freedom from cardiac events. The difficulties in gaining complete angiographic data were analyzed. Special emphasis was put on the problems and consequences resulting from incomplete angiographic follow-up.
This study consisted of retrospective and prospective data collection on the perioperative and mid-term course of all 89 patients who had undergone either MIDCAB or OPCAB surgery in our institution between January 1996 and September 2001. Patient records were consulted to collect data concerning the perioperative course. A follow-up visit served to collect data concerning the mid-term course. If no follow-up visit was possible, a telephone interview was conducted. If no telephone interview was possible with the patient, the primary physician was interviewed. Written informed consent was obtained from all surviving patients. The study was approved by the local institutional ethics committee. Between January 1996 and September 2001 a total of 29 patients underwent MIDCAB surgery in our institution. Patient characteristics are given in Table 1. MIDCAB surgery was performed through an anterolateral thoracotomy with a 10 cm incision and preparation of the fourth intercostal space, as described in the literature [6]. The reusable multi-retractor Schoellhorn (Karl Storz GmbH and Co.KG, Tuttlingen, Germany) or the single-use CTS stabilizer (CardioThoracic Systems Inc., Cupertino, CA, USA) was used for mechanical stabilization. The left internal mammary artery (LIMA) was used as graft material in 27 of the 29 patients (Table 2). One patient had a Y-graft; all other patients received only one anastomosis. Target area was the anterior wall in all but two patients.
Sixty patients underwent OPCAB surgery in our institution between January 1996 and September 2001. OPCAB surgery was performed as described in the literature [7]. A full median sternotomy was used for access. The reusable multi-retractor Schoellhorn or the single-use Octopus2-system (Medtronic Inc., Minneapolis, MN, USA) provided mechanical stabilization. In the OPCAB patient group, 47 patients received one anastomosis and 13 patients two anastomoses. Main target area was the anterior wall. Follow-up visits took place between May 2001 and August 2002, each consisting of a standardized questionnaire, physical examination, ECG, and echocardiography. The questionnaire focused on present clinical complaints, quality of life and cardiac events since surgery. We recommended all patients to submit to angiographic control of the anastomoses. Previous angiographic controls done due to clinical complaints were also considered for data analysis. A stenosis of 50% or higher was considered significant.
For statistical analysis, the Wilcoxon,
Patient characteristics are depicted in Table 1. Patient mean age at the time of surgery was 65 years (35–78 years), 14 patients were 75 years old or more. Patients with poor left ventricular function underwent primarily OPCAB surgery. The OPCAB patient group showed a higher mean preoperative risk score than did the MIDCAB patient group. In 26 cases an off-pump approach was chosen because of extensive comorbidity or extreme aortic calcification. There was no contraindication for CPB in 63 cases; the minimally invasive method was chosen as an alternative treatment to standard CABG. Table 2 shows the grafts used and the revascularization targets. In total, 103 anastomoses were constructed from 96 grafts. The LIMA was used in 88% of the patients. In three cases the LIMA was injured, requiring a vein interposition in two cases; in the third patient the LIMA was used as freegraft. The left anterior descending (LAD) was the most frequent target vessel; and only three patients had revascularization of the circumflex artery (CFX). In four patients the graft was not anastomosed to the native vessel directly but to a graft from a prior CABG. There were no perioperative deaths. Two patients suffered from perioperative myocardial infarction due to early graft failure, which required reoperation in standard technique in both cases (Table 3). A new postoperative neurological deficit with impaired motoric function was observed in two patients, symptoms that disappeared within days. The most frequent cardiac arrhythmia was new onset atrial fibrillation. Four patients required temporary pacemaker stimulation because of bradycard arrhythmia.
Median postoperative hospital stay was 7 days. Median period of time between surgery and job continuation was 14 weeks for the OPCAB patients and 8 weeks for the MIDCAB patients. Of the 19 patients who had not retired before surgery, 12 patients returned to work. Fifty-eight patients visited our department for follow-up examination. A telephone interview was conducted with 21 further patients and their primary physicians, making detailed follow-up data complete for 79 patients. Data concerning survival and cardiac events could be completed for all 89 patients through telephone interviews with primary physicians and patient relatives. Four patients had already died, two have temporarily moved to a foreign country. Neither a follow-up examination nor a telephone interview was possible in four patients for other reasons. Mean period of time between surgery and follow-up examination was 25 months (Table 4). The most frequent clinical complaints were angina pectoris, dyspnea, chest wall pain and reduced physical capability. Forty-two percent of the MIDCAB patients complained of lateral chest wall pain. None showed new neurological deficit.
Fig. 1 shows the number of patients in the different CCS classes for angina pectoris. The comparison between the preoperative state and the follow-up examination reveals a highly significant shift to lower classes of severity. The mean value improved from 2.1 to 0.8  In the follow-up examination, 47 out of 79 patients (59%) stated that they are totally angina-free (CCS 0). There were no significant differences between the MIDCAB and OPCAB patients.
The same highly significant improvement between the preoperative state and current situation could be observed concerning dyspnea using the NYHA classes. The mean value improved from 2.3 to 1.6. In the follow-up examination, 42 patients stated that they are dyspnea-free (NYHA I). There were no significant differences between the MIDCAB and OPCAB groups. In the questionnaire, patients were asked to judge whether their quality of life had improved, deteriorated or was unchanged since before surgery. Improvement was expressed by 53 patients (67%; Table 4). Patient quality of life was evaluated using the Karnofsky Scale. Forty-six patients (58%) in total could engage in all their habitual and desired activities, 10 of them with no symptoms (Karnofsky 100%), and 36 with slight symptoms (Karnofsky 90%). Echocardiography was performed in 80 patients. Comparison of left ventricular ejection fraction between the preoperative state and follow-up examination revealed only minimal differences. Angiographic controls were carried out in 46 patients with a mean period of 18 months after surgery (Table 5). Nineteen patients had already undergone angiographic control due to clinical symptoms prior to follow-up examination in our center. Angiography was elective in 27 patients free from significant clinical complaints. In all remaining cases either the patients or primary physicians refused the recommended angiographic control.
In the 46 angiographies carried out, a total of 53 anastomoses were controlled, 47 of which showed no occlusion (patency rate 89%, Fig. 2). Forty-two anastomoses (79%) were free of significant stenosis.
The subgroup of LIMA grafts revealed a higher rate of patent grafts compared to the patency of all grafts. Table 5 depicts the angiographic results separately for those patients who underwent elective control and those with symptoms who had clinically indicated angiographies. Patients with clinically indicated angiographies had a significantly lower rate of stenosis-free grafts. Fig. 3 illustrates the mid-term course of all 89 patients after MIDCAB or OPCAB surgery. It shows the survival and freedom from the cardiac events reoperation, PTCA and myocardial infarction. The 30-day survival was 100%. All but two patients survived the first year (98%). One patient died from mesothelioma after 6 months. A 78-year-old woman died 11 months after surgery (cause of death unknown). A 74-year-old man died of cardiac shock following myocardial infarction after 14 months. Cardiac death due to arrhythmia occurred in further three patients after 15, 16, and 50 months. Survival after 3 years was 94%, and event-free survival after 3 years was 80%.
Since their surgery four patients have suffered from a myocardial infarction, two of which occurred on the first postoperative day, leading to two of the three reoperations, as mentioned earlier. The third reoperation became necessary after 8 months. Eleven patients have required PTCA interventions so far, six patients during the first year. Some of those were necessary because of stenosis in the native coronary vessel system, others because of graft stenosis or occlusion. A RIMA graft with a subtotal stenosis was reopened in one patient. In two patients the planned revascularization of occluded grafts failed, and a PTCA in the native coronary system was performed instead.
Expectations linked to MIDCAB and OPCAB surgeries are diverse and include less perioperative mortality and morbidity, equal graft patency as in standard CABG, faster rehabilitation, and lower costs. Some studies concerning these issues note benefits for off-pump surgery, whereas others failed to demonstrate significant differences; several studies revealed specific problems associated with beating heart surgery [1,5,8,9]. This study does not attempt to answer these questions. It represents our experience from the first 89 patients and describes difficulties in the evaluation of these procedures' advantages and disadvantages. A special intention of this study was to analyze the problems and consequences of incomplete angiographic follow-up. Some critical aspects concerning the design of this study need to be mentioned. Since MIDCAB and OPCAB are only applied in a small group of selected low- and high-risk patients in our department, the number of patients treated is too small to make a solid judgment. The patients underwent two different surgical procedures, the patient group was heterogeneous, and the follow-up periods differed. The aim of this study was to carry out follow-up angiographic control of every patient regardless of the amount of time since surgery. Due to the various reasons mentioned above, the rate of angiographic follow-up was a little over 50% (46/89 patients). Many patients and primary physicians could not be convinced of the necessity for angiographic control in the absence of clinical complaints, and data from this group are therefore incomplete. On the other hand all patients with clinical symptoms underwent angiographic control, which we considered in these results regardless of the amount of time since surgery. The significantly higher graft stenosis rate in this group compared to the elective controls demonstrates this imbalance. Therefore these results represent a negative selection. Other studies defined an exact angiographic follow-up interval, e.g. 6 months. In these patency rates, only controls performed at this point of time were considered, cases of early graft failure were not counted. Therefore these data might have a positive bias. The broad dispersion of the EuroSCORE values of the patients indicates that patients with low risk, e.g. after failed interventional treatment were treated minimally invasive as well as a group of high-risk patients, e.g. with an extremely calcified aorta or with repeated CABG. This bimodal distribution of patients has been described especially for OPCAB patients [10]. In this study intraoperative and 30-day survival was 100%. The overall high level of EuroSCORE values with a maximum of 11 implies that OPCAB and MIDCAB are safe alternative procedures for high-risk patients in particular. This is also supported by the low rates of perioperative myocardial infarction, stroke, renal failure, and respiratory insufficiency. Follow-up examinations (mean follow-up period of 25 months) revealed fewer clinical complaints and an excellent quality of life in almost all patients. There was highly significant improvement compared to the preoperative state concerning angina pectoris (CCS 2.1 vs. 0.8) and dyspnea (NYHA 2.3 vs. 1.6). 42% of the MIDCAB patients complained of lateral chest wall pain due to the lateral thoracotomy, which suggests that anterolateral access does not reduce chest wall pain compared to median sternotomy. In this study, the angiographic controls in 46 out of 89 patients with a mean postoperative interval of 18 months revealed an overall graft patency rate of 89%. The highest patency rate was observed in the LIMA grafts (97% graft patency, 90% free from stenosis). Many authors have reported excellent early in-hospital graft patency rates of above 90% after MIDCAB or OPCAB surgery [10–13]. There is a lack of complete data concerning angiographic controls in the mid-term course. The problem of incomplete data acquisition is inherent in studies with angiographic follow-up taking place after hospital discharge. The most complete data were reported by Diegeler et al. who carried out angiographic control in 98 out of 110 patients 6 months after MIDCAB surgery. They found a 100% patency rate, and 82% of the anastomoses were free from stenosis greater than 50% [14]. In our study, the overall survival estimate was 98% after 1 year and 94% after 3 years. The event-free survival was 86% after 1 year and 80% after 3 years. Within the first year, six patients (7%) had to undergo PTCA. For the first 6 months after MIDCAB surgery, Diegeler et al. found a frequency of cardiac events similar to ours, the event-free survival was significantly higher than for patients treated with PTCA in the same study. In the MASS study, patients after standard CABG were shown to have a significantly higher event-free survival rate (91.4% after 5 years) compared to patients treated with PTCA or medication only. These results suggest that both off- and on-pump surgeries provide good survival and freedom from cardiac events. However, such benefits still need to be proven over the long-term course for off-pump surgery. In conclusion, the perioperative complication rate in this study was acceptable with regard to patient comorbidity. The results concerning improvements in clinical symptoms, quality of life, survival, and freedom from events were excellent. The angiographic data are not complete enough to allow a definite judgment of the quality of the anastomoses. It was not possible to perform angiographic controls in all patients since some of them and their primary physicians could not be convinced of the necessity of this control in the absence of clinical complaints. The complete angiographic follow-up of the patients with clinical complaints on one hand and the incomplete follow-up of the asymptomatic patients on the other hand yields to a negative bias. In selected patients, especially those with high risk for standard CABG, beating heart surgery seems to be a valuable alternative with good results. At this time, it seems questionable that off-pump surgery should be extended to all patients. Further studies will have to evaluate long-term course and graft patency after off-pump surgery.
ICVTS on-line discussion Author: Dr. Hitoshi Hirose, Juntendo University Hospital, Department of Cardiovascular Surgery, Overlook Rd 312, Cleveland, OH 44106, USA Date: 08-Feb-2004 Message: It is an interesting paper about mid-term results of off-pump CABG. I agree with the authors that it is difficult to perform postoperative angiography on everybody who has had a surgery. In our institution, we performed 593 off-pump CABG between January 1996 and September 2001, which is the same period of the author's study. The mean age of our study was 67.3 %b1 9.2, Euro SCORE 3.9 %b1 2.7, three vessel disease 336 patients (56.7%), and left main stenosis 144 patients (24.3%). Of these, 120 (20.2%) underwent MIDCAB (single vessel revascularization via mini-thoracotomy incision). Mean number of bypass was 3.0 %b1 1.1 if MIDCAB patients were excluded. Postoperative angiography was performed in 359 patients within 3 months of surgery and there were 7 occlusions and 50 stenosis, giving overall graft patency rate of 99.2%, stenosis-free patency rate of 93.1%. Follow- up data was available to all patients with a mean interval of 18 %b1 12 month. During the follow-up, there were 32 deaths (5.4%) and 38 cardiac events (6.5% - the definition of cardiac events were recurrence of angina, acute myocardial infarction, or coronary re-intervention, as described by authors). There were only 35 patients (5.9%) who underwent angiography beyond 3 months after surgery. It showed 8 occlusions and 9 stenoses, giving a graft patency rate of 88.9% and stenosis-free patency rate of 76.4%. Among 38 patients who had cardiac events, 16 cases (42.1%) were due to a graft occlusion or stenosis, 15 (39.4%) were due to incomplete revascularization, and 7 (20%) were due to de-novo coronary artery disease. Our observations are similar to the authors. However, the number of distal anastomosis has been increased (3.0 %b1 1.1 prior to September 2001 versus 4.0 %b1 1.3 after October 2001), because of advance in off-pump techniques. The complete revascularization rate has approached 93.4% in our institution. This advancement of off-pump CABG probably reduces the incidence of postoperative cardiac events. doi:10.1016/j.icvts.2004.01.003
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Abstract
1. Introduction
or Fisher's exact test were used where appropriate. The Kaplan–Meier method was used to illustrate survival and cardiac events in the mid-term course. 
