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Eur J Cardiothorac Surg 2001;20:120-126
© 2001 Elsevier Science NL
a Department of Cardiac Surgery, University of Heidelberg, Neuenheimer Feld 110D-69120, Heidelberg, Germany
b The Cleveland Clinic Foundation, Department of Thoracic and Cardiovascular Surgery, Department of Biostatistics and Epidemiology, Cleveland, OH, USA
Received 11 November 2000; received in revised form 13 March 2001; accepted 4 April 2001.
Corresponding author. Tel.: +49-6221-566111; fax: +49-6221-56 5585
e-mail: brigitte_osswald{at}med.uni-heidelberg.de
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Abstract |
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 Top Abstract 1. Introduction2. Patients and methods3. Results4. DiscussionAppendix AAppendix BAppendix C. Conference...References |
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Key Words: Coronary artery bypass grafting • Incomplete revascularization: Elderly patients
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1. Introduction |
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TopAbstract1. Introduction2. Patients and methods3. Results4. DiscussionAppendix AAppendix BAppendix C. Conference...References |
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2. Patients and methods |
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TopAbstract1. Introduction2. Patients and methods3. Results4. DiscussionAppendix AAppendix BAppendix C. Conference...References |
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2.2. Data acquisition and data management
For documentation of about 1500 items per case, tools of the Heidelberger Verein zur multizentrischen Datenanalyse e.V. (HVMD) were used [4,5]. Because all data are collected at the point of care and serve to create both medical reports and a scientific data base, the quality of the primary data is reliable. A regular follow-up procedure by questionnaires is performed at the 180th postoperative day. For the investigated group, follow-up completeness was 95.6%.
2.3. Definition of incomplete revascularization
Incomplete revascularization, according to the definition of the HVMD is the omission of revascularization of at least one vessel which was preoperatively evaluated for bypass grafting out of the preoperative diagnostics (coronary angiography, in some cases stress echocardiography and/or Technetium (Tc)-99 pyrophosphate scanning), judged by the responsible surgeon.
2.4. Statistical analysis
For statistical analysis, SAS® (SAS Institute, Cary, USA) Version 6.12 was used. Data are presented as mean±standard deviation. The analysis was performed using descriptive methods, contingency tables and Wilcoxon 
2 test, Student's unpaired t-test, logistic regression, Kaplan–Meier non-parametric estimation methodology [6], a rank statistics used to test homogeneity between the strata [7] and the parametric, time-adjusted Hazard Function by Blackstone et al. [8]. Investigated variables and the specification of the parametric, time-adjusted hazard function are summarized in Appendix B.
For reducing the potential selection bias between patients with or without incomplete revascularization, we matched, subclassified and adjusted the data using propensity score methodology. First, the event incomplete versus complete revascularization was analyzed as the dependent variable by multivariable logistic regression independent from outcome using the variables listed in Appendix B. After this and investigation of potential interactions, the era of operation and risk factors not represented in the parsimonious model were added to form the propensity model. The area under the receiver operating curve for the model was 0.81. The propensity model was then used to calculate a propensity score for each patient. The predicted likelihoods of incomplete revascularization ranged from 0.0003 to 88.7%. All patients were sorted by propensity score and compared within quintiles [9]. The groups were well-matched. The propensity score as a logit unit and its transformation into a probability estimate were incorporated as continuous variables to adjust for possible confounding [10].
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3. Results |
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TopAbstract1. Introduction2. Patients and methods3. Results4. DiscussionAppendix AAppendix BAppendix C. Conference...References |
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4. Discussion |
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TopAbstract1. Introduction2. Patients and methods3. Results4. DiscussionAppendix AAppendix BAppendix C. Conference...References |
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4.2. Interpretation of findings
In different studies, the beneficial effect of complete revascularization on long-term survival supports theoretical considerations [11–14]. It is to be stressed, that obviously the diagnostic methods did not succeed in reflecting adequately the intraoperative status of the coronary arteries. So, an underestimation of the severity of coronary disease in patients with incomplete revascularization is likely. Therefore, the higher risk of death early after incomplete revascularization may be the simple consequence of an advanced disease state that cannot be detected prior to any surgical or interventional effort. Although we did not observe a decisive bias between the patients with incomplete or complete revascularization concerning the preoperative cardiac and non-cardiac comorbidity out of the preoperatively performed examinations, underestimation of the disease is likely. However, this underestimation occurs independent on the therapeutic approach. The direct tactile and visual impressions of the status of the coronary arteries during open heart surgery is still a major advantage of the conventional approach, because neither the minimally invasive nor primary interventional methods so far succeed in giving the information necessary for judgement of the coronary vessel status.
The definition of incomplete revascularization in our study has been chosen by the surgeon's intention to treat. This is in contrast to other studies that compared the number of vessels with a stenosis of greater than or equal to 50% from coronary angiography with the number of grafted vessels [15]. However, in clinical practice, 50% stenoses and sometimes even high-degree stenoses are not necessarily considered for bypass grafting; this is especially true for septal, small diagonal and small marginal branches or peripheral parts of the right coronary system. Another definition by Sergeant et al. [14] compared the number of vessels with a diameter of at least 1.5 mm and a stenosis 
70% with the number of grafted vessels. In the CASS study, the beneficial effect of complete revascularization on long-term results after CABG was shown; the study included only patients with three-vessel disease and indicated a non-revascularization of the at least one of the three systems to be incomplete [11].
Despite these different definitions, a clear message is, that better outcome occurs with complete revascularization.
4.3. Clinical inferences
The proportion of patients with incomplete revascularization remains at about 15%. In the era of minimally invasive surgery, an increasing number of patients are called eligible for the minimal invasive approach by inclusion of patients with multi-vessel disease [16,17]. Because incomplete revascularization predominantly has been described as a risk factor in the long term, elderly patients may be an ideal group for incomplete intervention, since demography itself prevents most patients from experiencing adverse events. However, at least in this group of elderly patients, the beneficial impact of complete revascularization on early survival justifies to perform complete revascularization as the method of choice as well in elderly patients. Furthermore, recently Blackstone and Lytle succeeded in showing, that even elderly patients profit by surgical procedures with proven beneficial long-term effects [18].
The majority of patients in our study has been incompletely revascularized because of small vessels. The question arises ‘How small is too small?’ In a study of Corbineau et al. [19], age over 70 was found to represent an independent risk factor for an impaired run-off of grafted vessels which indicates, that coronary arteries in elderly patients are more diffusely diseased.
The potential advantage of shorter aortic cross-clamping time, especially in the older patient group, could not be confirmed by our analysis. However, the intention to treat includes a careful consideration of the surgeon according to each individual coronary status, so that a primary incomplete approach might have been accompanied by shorter aortic cross-clamping and operation time. However, it remains questionable, whether even a more prolonged extracorporeal circulation for plus/minus one or two distal anastomoses in the range of 10–30 min would have substantial effect on early mortality.
4.4. Limitations of the study
Observational studies such as this one bear the risk of a systematic bias of the investigated groups, such as patients with complete or incomplete revascularization. Thus, the observed differences in survival could relate to the underlying reason that the intended revascularization was not performed. This may be different from deliberate election not to revascularize an area. Because the decision to completely or incompletely revascularize a given patient was not made at a random, direct comparison of outcome may be biased. Therefore, we first attempted to adjust for selection factors by multivariable analysis, investigating outcome by both multivariable logistic regression and time-related analysis. In addition, we used propensity score matching of patients, including various variables concerning the coronary status and further variables of cardiac and non-cardiac comorbidity. Both strategies for reducing potential bias from selection identified that patients with incomplete revascularization were at higher risk of mortality than those completely revascularized.
5. Conclusion
Incomplete revascularization reduces early survival after CABG in elderly patients. Therefore, the beneficial effects of complete revascularization should be kept in mind if any approach for incomplete revascularization is considered. Perhaps, in these cases, a more conservative approach may help to avoid adverse early and late effects of ‘intended’ incomplete revascularization.
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Footnotes |
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Appendix A |
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TopAbstract1. Introduction2. Patients and methods3. Results4. DiscussionAppendix AAppendix BAppendix C. Conference...References |
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Age, male, weight, year of surgery, unstable angina, smoking, obesity, hypertension, preoperative on diuretics, dyspnea at exercise, ejection fraction, end-diastolic left ventricular pressure, LV aneurysm, LV dilatation, LV akinesia, left main disease, LAD occlusion, peripheral vascular disease, diabetes, pulmonary obstructive disease, renal disease, dialysis-dependency, preoperatively on ß-blocker, preoperative sinus-rhythm, permanent pacemaker, number of previous cardio-thoracic surgery, use of IMA, urgency, incomplete revascularization.
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Appendix B |
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TopAbstract1. Introduction2. Patients and methods3. Results4. DiscussionAppendix AAppendix BAppendix C. Conference...References |
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Early phase: Mue=0.09 Thalf=10.9 nu=0 m=-1.7, Delta=0, Rho=30.3.
Constant phase: Muc=3.6E-05.
B.2. 2. Variables at the beginning of the multivariable analysis of death
Demographic
Gender, age (years) at operation, weight, height, body mass index, obesity (men: height in cm: 90, women: height in cm: 100).
Cardiac comorbidity
NYHA (1, mild; 2, mild symptoms; 3, symptoms with normal activities; 4a, severe with symptoms at rest; 4b, unstable angina), Holper (1, mild; 2, mild symptoms at higher degree of physical stress; 3, symptoms at mid degree of physical stress; 4, symptoms at low degree of physical stress; 5, stable out of unstable angina; 6, beginning unstable angina; 7, unstable angina; 8, cardiogenic shock), severe heart failure in history, subjective impression of heart failure, clinical sign of heart failure, dyspnea at excercise, dyspnea at rest, excercise-related angina, angina at rest, treatment for unstable angina (0, neither oral nor i.v.-medication. 1, oral medication; 2, intravenous medication), pathologic valvular findings without neccessity for surgical treatment, urgency of operation (elective, urgent, emergent, emergent+CPR).
Left ventricular function
Normal left ventricular size, left ventricular hypertrophy, left ventricular dilatation, left ventricular hypokinesia, left ventricular akinesia, left ventricular aneurysm, systolic aortic pressure, diastolic aortic pressure, mean aortic pressure, left ventricular systolic pressure, left ventricular enddiastolic pressure, left ventricular function qualifier (0, good; 1, fair; 2, bad). Ejection fraction was available for only 63% of all patients, acute myocardial infarction, chronic pulmonary edema, acute pulmonary edema, cardiogenic shock.
Preoperative drugs
Diuretics, ACE inhibitors, antibiotics, aspirin, digitalis, ß-blocker, calcium antagonists, anticoagulation, antiarrhythmic agents, any preoperative drug.
Non-cardiac comorbidity
Smoking, diabetes, hyperlipoproteinemia, hypertension, hyperuricemia, positive family history, any of the known, risk factors, syncope, embolism, gastrointestinal disease, extracardiac vascular disease, calcified aortic wall, pulmonary obstructive disease, pulmonary restrictive disease, any pulmonary disease, renal disease, dialysis dependency, neurologic disease.
Coronary status
Number of affected vessels, diffuse arteriosclerotic affection of coronary arteries, left main disease, dominant vessel, number of coronary vessels disease 50%, 70%, 90%, 100% stenosis, number of coronary systems disease 50%, 70%, 90%, 100% stenosis, stenosis of LAD 50%, 70%, 90%, 100%, stenosis of RCA 50%, 70%, 90%, 100%, stenosis of Circumflex artery 50%, 70%, 90%, 100%, diagonals.
Preoperative rhythm
Sinus rhythm, atrial fibrillation, ventricular tachycardia, pacemaker, ventricular ectopic beats.
Previous procedures
PTCA, coronary stent implantation, laser ablation, complication of PTCA, unsuccessful PTCA, bypass occlusion, bypass stent implantation, thrombolytic therapy (within the last 14 days), reoperation for CABG, number of previously performed CABG procedures.
Surgical strategy
Use of IMA, incomplete revascularization, surgeon.
B.3. 3. Selected variables (coefficients, standard error, P values)
Early phase: Intercept:-2.409.
Diabetes, 0.4±0.2, P=0.04, chronic pulmonary edema, 0.8±0.3, P=0.03, incomplete revascularization, 0.8±0.2, P=0.001, emergent operation, 0.8±0.3, P=0.007.
Constant phase: Intercept: -10.2197.
Acute heart failure in history: <0.0001±2.0, P=<0.0001, preoperative on aspirin, 1.1±0.5, P=0.04, renal disease, 2.1±0.5, P=0.0001.
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Appendix C. Conference discussion |
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TopAbstract1. Introduction2. Patients and methods3. Results4. DiscussionAppendix AAppendix BAppendix C. Conference...References |
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Dr Osswald: That's maybe true.
Dr Perko: So I think that the design of this study is wrong and the conclusions are misleading.
Dr Osswald: It depends on what you want to discuss, because if you look at patients with a preoperative status only, you have only coronary angiography, you have the diagnostic steps which you can go, but during operation you have perhaps a completely different status. However, if any different therapy is chosen, you do not know out of the preoperative available information the direct coronary status. This has been one of the points I wanted to stress, because whether you perform minimally invasive CABG, PTCA or conventional CABG, you do not know whether the coronary status is correctly reflected by the preoperative diagnosis.
Dr P. Sergeant (Leuven, Belgium): My comments are very similar but maybe differently formatted than the previous commentator. Basically what you have shown is information about involuntary incomplete revascularization.
Dr Osswald: This is true.
Dr Sergeant: And I think that this needs to be differentiated from voluntary incomplete revascularization. You are pointing very well and very clear that there is a major risk at the voluntary incomplete revascularization, but in these 75-year-old patients we are very often confronted with an involuntary situation.
Dr E. Covino (Catanzaro, Italy): After all, I agree with the conclusions of this study; however, I would have liked to know which coronaries are not revascularized. In fact, it may make a difference to neglect an important or a less important coronary artery.
Dr Osswald: Well, if we are looking at these incomplete versus complete, we just have decided out of the preoperative diagnostic to operate on that vessel. Most of these vessels are major vessels like the circumflex, the LAD or the RCA, however, it is very likely that you might have even prominent vessels which are the smaller ones, the marginals, the diagonals, whatever. The coronary status is highly individual, so that we are including all of the vessels selected for revascularization.
Dr J. Melo (Carnaxide, Portugal): I think you are raising an important issue. My first reaction was like the previous speakers. It is difficult to understand that you have performed incomplete revascularization but the cross-clamp time for both groups is the same. So what was the number of grafts per patient in each group? What was the number of LADs that were not grafted on the incomplete revascularization? The differences between groups happened in the first 30 days after surgery. What were the major reasons for this?
Dr Osswald: Well, to address the first part, we have had no patient where we just decided primarily to do an incomplete revascularization. We intended to do the complete revascularization in all of these patients. It was not too surprising that we did have no big differences in the aortic cross-clamping time, because we intended to perform total revascularization. It is probably completely different for the minimally invasive groups where you will have a shorter aortic cross-clamping time, because you primarily do not intend to do complete revascularization.
The reasons for the deaths after CABG, we have not yet divided between different groups, however, most of them have had an LV function dysfunction.
Dr D. Saksena (Bombay, India): I would like to take issue with one of the statements that you made. The implications of this study are on minimally invasive or OPCAB surgery, because I believe OPCAB is more like an angioplasty and when you don't clamp the aorta, you don't go on a heart-lung machine, the mortality in the early period will not be any different if you leave one or two vessels which are not critically blocked alone, as the cardiologists do when performing angioplasty. Now, in a 75-year-old patient I agree that if you don't do a complete revascularization, the long-term results might not be that good, but the immediate results are satisfactory with low mortality unlike you have shown when you have done the patients bypass.
Dr Osswald: This was an issue of our investigation to show that early mortality represents an important aspect of incomplete revascularization. Retrospectively, any less invasive procedure could have been beneficial for those patients who received incomplete revascularization. However, all of the patients have been carefully selected for the conventional CABG out of their preoperative cardiac and non-cardiac status. To do incomplete revascularization is in all of the cases decided when the patient is already on cardiopulmonary bypass. Therefore, a less invasive or OPCAB procedure does not represent an alternative. Whether the early deaths are primarily related to the adverse effects of extracorporeal circulation cannot be answered. However, from the ethical and medical point of view, it is and hopefully will be not justified to withhold the beneficial effects of complete revascularization generally from elderly patients and to perform either of the available incomplete interventions as the intervention of choice only because of age.
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TopAbstract1. Introduction2. Patients and methods3. Results4. DiscussionAppendix AAppendix BAppendix C. Conference...References |
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