Ann Thorac Surg 2004;78:487-491
© 2004 The Society of Thoracic Surgeons
Original article: cardiovascular
Impact of multivessel coronary artery disease on outcome after isolated minimally invasive bypass grafting of the left anterior descending artery
Artur Lichtenberg, MDa*,
Uwe Klima, MD, PhDa,
Hans Paeschkea,b,
Max Pichlmaier, MDa,
Stefanie Ringes-Lichtenberg, MDb,
Thorsten Walles, MDa,
Heidi Goerler, MDa,
Axel Haverich, MD, PhDa
a Division of Thoracic and Cardiovascular Surgery, Hannover Medical School, Hannover, Germany
b Department of Cardiology and Angiology, Hannover Medical School, Hannover, Germany
Accepted for publication November 25, 2003.
* Address reprint requests to Dr Lichtenberg, Division of Thoracic and Cardiovascular Surgery, Hannover Medical School, 30623 Hannover, Germany
e-mail: lichtenberg{at}thg.mh-hannover.de
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Abstract
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BACKGROUND: The outcome in patients treated surgically for coronary artery disease is known to be influenced by the extent of the disease. Whether this factor also has an effect in patients undergoing isolated minimally invasive revascularization of the left anterior descending (LAD) artery using the internal thoracic artery (ITA) (MIDCAB) has not been looked at. Thus, this study sought to evaluate the impact of multivessel disease (MVD) on midterm outcome after MIDCAB.
METHODS: From 1996 to 1999, 411 patients received a MIDCAB at our institution and were now followed up. Isolated disease of the LAD (SVD –single vessel disease) was presented in 262 patients (63.7%) and 149 patients (36.3%) had MVD at the time of operation. The reasons for apparent incomplete revascularization in patients with MVD were very small target vessels (< 1.0-mm diameter), stenoses of less than 50%, distal localization of the stenoses, long-term patency after angioplasty, or an extensive risk for sternotomy and(or) cardiopulmonary bypass. The midterm outcome was evaluated by questionnaires sent to the patients and their physicians.
RESULTS: The mean follow-up was 29.4 ± 11.1 months. The incidence of myocardial infarction was significantly higher in MVD as compared to SVD patients (8.1% vs 1.9%, p = 0.04). Patients with MVD had significantly more subsequent percutaneous transluminal coronary angioplasty (10.7% vs 5.3%, p = 0.049) and a similar number of repeat surgical revascularizations as compared to SVD patients. Patients with MVD had a significantly higher total 3-year mortality as compared to SVD patients by Kaplan-Meier estimate (8.7% vs 3.1%, relative risk [RR] = 2.56, p = 0.011). The 3-year cardiac mortality was significantly higher in patients with MVD as compared to SVD (4.0% vs 0.4%, RR = 9.48, p = 0.0054). After adjustment of baseline characteristics by Cox regression analysis, the 3-year risk of cardiac death was significantly higher in the MVD groups (RR = 2.2, confidence interval [CI] 95%: 1.8 to 4.65, p = 0.029).
CONCLUSIONS: Patients with isolated disease of the LAD appear to benefit from ITA grafting in the form of a MIDCAB procedure. Here, it should be an approach of choice. The results show that MVD is an independent risk factor for outcome in patients undergoing a MIDCAB procedure. Nevertheless, the midterm morbidity and mortality in MVD patients after a MIDCAB procedure where the LAD is the only target vessel for interventional or surgical treatment is acceptable despite a higher morbidity than in SVD patients.
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Introduction
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Minimally invasive coronary artery bypass grafting (MIDCAB) is accepted as a safe and reliable surgical procedure for myocardial revascularization of proximally stenosed left anterior descending (LAD) arteries [1]. The left internal thoracic artery (ITA) is utilized for bypass grafting through an anterolateral mini-thoracotomy and cardiopulmonary bypass (CPB) is not required [2, 3]. Several studies have shown excellent short-term results, with low morbidity and mortality, after MIDCAB procedures [1–5].
Long-term trials have identified predictors of mortality after standard coronary artery bypass grafting (CABG) using CPB. Here, the presence of multivessel coronary artery disease (MVD) has a significant negative impact on long-term results [6–9]. Until now, however, it has been unclear whether this factor also influences the intermediate and long-term outcome in patients after minimally invasive isolated LAD grafting on the beating heart using the ITA (MIDCAB). In this study the impact of MVD on the occurrence of adverse events and survival for in-hospital and midterm observation in patients following MIDCAB was evaluated.
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Material and methods
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A total of 411 patients who underwent isolated revascularization of the LAD at our institution between June 1996 and December 1999, using the ITA by a limited access approach through an anterolateral left minithoracotomy on the beating heart without CPB, were evaluated during a midterm follow-up. During this period 2,845 patients underwent conventional coronary artery bypass surgery (CAB) using CPB. Of those, 27 (1.0%) patients had an isolated LAD grafting with the ITA through a conventional midline sternotomy .
Five patients of the MIDCAB group were lost to follow-up. These were not included in the study. We also excluded 44 patients who underwent combined surgical and interventional ("hybrid") procedures (MIDCAB + angioplasty).
Isolated proximal stenoses or an occlusion of the LAD were present in 262 (63.7%) patients, whereas 149 (36.3%) patients had MVD at the time of the MIDCAB procedure. Of those with MVD, 102 (24.9%) patients had double-vessel and 47 (11.4%) patients had triple-vessel disease. The reasons for the apparent incomplete revascularization in our MIDCAB patients were described previously [3]. Multivessel coronary artery disease patients with small vessels (< 1.0-mm diameter) unsuitable for bypass grafting with either a very limited target area of a myocardial perfusion or extensive myocardial scar in the right coronary and(or) circumflex arteries, stenoses less than 50% by diameter, long-term patency after angioplasty, or extensive risk for sternotomy and(or) CPB were scheduled for MIDCAB procedure.
Demographic, intraoperative, and in-hospital data of all MIDCAB procedures were collected and entered into the database. Baseline characteristics included age, sex, body mass index (BMI), and cardiac risk factors such as diabetes, hypertension, smoking status, and hyperlipidemia. Comorbidity was defined as the presence of organ dysfunction or insufficiency (chronic obstructive pulmonary disease [COPD], cerebral deficit, chronic renal failure, liver insufficiency), vascular disease (sclerosis of the ascending aorta, nonascending aneurysm, peripheral, cerebrovascular disease, previous pulmonary embolism), active malignances, systemic immunosuppression, systemic coagulation disease, or previous sternal osteomyelitis. Follow-up data were collected using a standardized questionnaire answered by the patients and their physicians.
The study end points included total and cardiac-related late mortality (> 30 days after surgery), myocardial infarction, and need for repeat revascularization. The criteria for myocardial infarction (MI) were a new onset of Q waves or elevation of cardiac enzymes (creatinine kinase [CK] peak-levels and MB fraction) accompanied by an elevation of ST segments in electrocardiographic examinations (ECG). A CK rise above two times the normal range without a new Q wave on the ECG was considered a non-Q-wave MI. Furthermore, the differences in medical treatment (use of nitrates, ß blockers, ace inhibitors, lipid-lowering agents, and platelet inhibitors) between the study groups during the observation period were specifically compared.
Statistical analysis
The data are presented as mean ± standard deviation for continuous variables or number and percentages for dichotomous variables. Univariate analysis of categorical data were carried out using the 
2 or Fisher's exact tests. Univariate analysis of normally distributed continuous variables was carried out using the Student's t test. Kaplan-Meier estimates were used to calculate total and cardiac-related survival; Kaplan-Meier curves were compared using the long-rank test. Multivariate Cox regression analysis served to examine baseline characteristics to identify independent risk factors for cardiac mortality among the patient populations (MVD and single-vessel disease [SVD]). The model included age, sex, BMI, angina status, left ventricular ejection fraction, diabetes mellitus, history of smoking, hypertension, hyperlipidemia, comorbidities, and number of diseased vessels. A p value less than 0.05 was considered to indicate statistical significance. The SPSS statistical software package 11.0 for Windows (SPSS Inc., Chicago, IL) was used for statistical analysis.
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Results
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Baseline characteristics
Demographic data and baseline characteristics of patients with SVD and MVD are listed in Table 1. There were more women in the MVD group. Other organ dysfunction, sclerosis of the ascending aorta, concomitant peripheral vascular disease, and cerebrovascular disease were significantly more common in MVD patients. Previous cardiac surgery was also more often found in MVD patients (Table 2).
In-hospital outcome and control angiography
Table 3 depicts the in-hospital outcome of patients with SVD and MVD after MIDCAB. There was no statistical difference in occurrence of in-hospital death, myocardial infarction, or stroke. The incidence of wound dehiscence and infection was similar among MVD and SVD patients.
Of all the patients included in the study 69% (n = 286) underwent control angiography, which was performed in 257 (62.5%) patients within 1 year of surgery and in 29 (7.1%) patients thereafter. The patency rate of ITA grafts was comparable between the study groups (Table 4).
Follow-Up
All of the 411 patients were successfully followed up 29.4 ± 11.1 months after surgery. Figure 1 shows the cumulative rates of total survival for the two subgroups of MIDCAB patients. Patients with MVD had significantly higher total, as well as cardiac-related, mortality compared to SVD patients (Kaplan-Meier rates 8.7% [13 patients] vs 3.1% [8 patients], relative risk [RR] = 2.56, p = 0.011 by log-rank test; 4.0% [6 patients] vs 0.4% [1 patient], RR = 9.48, p = 0.0054 by log-rank test, respectively] (Figs 1 and 2).
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Fig 1. Cumulative total survival of patients according to the presence or absence of MVD. · · · = SVD; – · – = MVD. (MVD = multivessel disease; RR = relative risk; SVD = single-vessel disease [isolated left anterior descending coronary artery lesion].)
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Fig 2. Cumulative cardiac survival of patients according to the presence or absence of MVD. · · · = SVD; – · – = MVD. (MVD = multivessel disease; RR = relative risk; SVD = single-vessel disease [isolated left anterior descending coronary artery lesion].)
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Patients with double-vessel (2VD) or triple-vessel (3VD) disease revealed a similar total mortality as can be seen from the Kaplan-Meier survival curves (2VD vs 3VD: 8.8% [9 patients] vs 8.5% [4 patients], RR = 1.04; p = 0.88 by log-rank test]. Cardiac mortality rate, however, was slightly lower in patients with 2VD compared to 3VD patients but this trend did not achieve statistical significance (2VD vs 3VD: 2.9% [3 patients] vs 6.4% [3 patients], RR = 0.46, p = 0.40 by log-rank test] (Fig 3).
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Fig 3. Cumulative total and cardiac survival in patients with double-vessel compared to triple-vessel disease (total survival: — = 2VD; --- = 3VD) (cardiac survival: – · – = 2VD; · · · = 3VD). (2VD = two-vessel disease; 3VD = three-vessel disease; RR = relative risk.)
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Table 5 depicts cumulative rates of myocardial infarction, and subsequent revascularization during follow-up. The incidence of myocardial infarction was significantly higher in MVD as compared to SVD patients (8.1% vs 1.9%, p = 0.04). Patients with MVD had significantly more subsequent percutaneous transluminal coronary angioplasty (PTCA) (10.7% vs 5.3%, p = 0.049), but had a similar number of repeat surgical revascularizations compared to SVD patients.
Multivariate Cox regression analysis revealed MVD as important independent predictors of 3-year cardiac mortality (RR = 2.2, confidence interval [CI] 95%: 1.8 to 4.65, p = 0.029). Patients with MVD were found to take significantly more nitrates as compared to the SVD group (30.1% vs 19.7%, p = 0.015). Regarding ß blockers, ace inhibitors, lipid-lowering agents, and platelet inhibitors no significant differences were found between the groups. The influence of medical treatment on midterm morbidity and mortality showed no significant differences between the groups.
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Comment
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In agreement with the current literature for CAB surgery, the results of this study demonstrate a significantly worse intermediate (3-year) outcome after MIDCAB procedures in patients with multivessel coronary artery disease as compared to patients with isolated LAD disease [10]. Previous investigations have shown an inferior cardiac long-term survival in patients with MVD as compared to SVD patients [8–11]. Our results confirm this, showing that patients with double-vessel and triple-vessel disease receiving isolated LAD grafting using ITA on the beating heart had a significantly poorer total and cardiac 3-year survival as compared to patients with isolated proximal stenoses or occlusions of the LAD. Despite this difference, the late mortality rates for both groups were comparable to those in the literature [8].
The proportion of MVD patients in the study population (36.3%) appears higher than in other series [12, 13]. The decision for the MIDCAB approach in our MVD patient population was made first on the basis of the coronary vessels morphology, and second on the relative risk profile for conventional surgery [3]. The individual decision in favor of an incomplete surgical revascularization on the basis of angiographic findings is difficult and, despite the high quality of current coronary artery angiograms, often subjective. In our cohort such decisions were made in close agreement between the surgeon and the cardiologist involved. In patients with a dominant proximal stenosis of the LAD, who had concomitant other stenoses mainly in the terminal segments of the circumflex and(or) right coronary artery territories with a small vessel diameter (< 1.0 mm), as well as a small myocardial target area or myocardial scars for a revascularization, a MIDCAB procedure was generally preferred [3].
Patients with MVD presented with an unfavorable initial risk constitution including more severe ischemia as well as cardiac damage before surgery compared to SVD patients. Nevertheless, operative and hospital mortality and morbidity data were comparable between MVD and SVD patients. Surgical revascularization of stenotic non-LAD vessels in the MVD group was deemed either impossible or unnecessary due to very small target vessels (< 1.0-mm diameter), stenoses of less than 50%, distal localization of the stenoses, long-term patency after angioplasty, as well as an unacceptable risk for conventional bypass surgery using CPB by severe organ dysfunction or insufficiency, active malignances, systemic immunosuppression, or previous sternal osteomyelitis [3]. We acknowledge that complete revascularization must be the aim of CAB surgery and remains one of the most important factors for long-term results following surgery [11]. For the MVD patients in our study population with additional diseased non-LAD vessels not amenable to surgery or cardiologic intervention, the concept of complete revascularization was not applicable.
In both our groups an occurrence of restenosis after previous angioplasty or primary moderate and high risk lesions of the proximal LAD (American Heart Association lesion classification system) were the main indications for a surgical revascularization of the LAD [14]. The cardiologic interventions for the LAD lesion in these patients were primarily associated with a high procedural risk as well as a high risk for an occurrence of subsequent restenosis with, nevertheless, possible necessity of a further surgical revascularization. The fact that cardiologic interventions are accompanied by a higher incidence of repeat interventions, as well as with a lower freedom from angina due to occurrence of the restenosis [15, 16], emphasizes the superiority of surgical approach in the form of a MIDCAB procedure in patients with the LAD as the only target vessel for revascularization [1].
Limitations
The authors recognize limitations in the design and the interpretation of the present study. It is an observational clinical study. The follow-up data were collected retrospectively. An objective evaluation as to the progression of the coronary disease such as myocardial viability studies and(or) serial angiographic examinations were not performed.
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Conclusions
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Treatment of a proximal high-grade LAD lesion by MIDCAB in MVD patients, if complete revascularization is not possible, is safe and effective. From the patients' management point of view we conclude that patients with single-vessel disease of the LAD should be recruited for MIDCAB as a first choice of treatment. In MVD patients where the LAD is the only target vessel for interventional or surgical treatment, again ITA grafting in the form of a MIDCAB procedure is the approach of choice.
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References
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Abstract
Introduction
