ATS
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
 QUICK SEARCH:   [advanced]


     


This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to Personal Folders
Right arrow Download to citation manager
Right arrow Author home page(s):
Paul T. Sergeant
Eugene H. Blackstone
Bart P. Meyns
Right arrow Permission Requests
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Sergeant, P. T.
Right arrow Articles by Meyns, B. P.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Sergeant, P. T.
Right arrow Articles by Meyns, B. P.

Ann Thorac Surg 1998;66:1-11
© 1998 The Society of Thoracic Surgeons


J. Maxwell Chamberlain Memorial Paper

Does arterial revascularization decrease the risk of infarction after coronary artery bypass grafting?

Paul T. Sergeant, MD, PhDa, Eugene H. Blackstone, MDa, Bart P. Meyns, MD, PhDa

a Cardiac Surgery Department, Gasthuisberg University Hospital, Leuven, Belgium

Address reprint requests to Dr Sergeant, Cardiac Surgery Department, Gasthuisberg University Hospital, Herestreet, 3000 Leuven, Belgium

Presented at the Thirty-fourth Annual Meeting of The Society of Thoracic Surgeons, New Orleans, LA, Jan 26–28, 1998.

Abstract

Background. This study sought to determine whether extensive arterial grafting reduces the prevalence and consequences of infarct after coronary artery bypass grafting.

Methods. Post-primary coronary artery bypass grafting infarcts and time-related events thereafter were identified by 99.9% complete follow-up of 9,600 patients (1971 to 1992). The contribution of arterial grafting to freedom from infarct was assessed by multivariable hazard function analysis to adjust for other risk factors.

Results. Unadjusted 1-month and 10-year freedom from infarction was 97% and 86%. By multivariable analysis, arterial grafting lowered the prevalence of periprocedural (p = 0.005), intermediate term (p = 0.007 and 0.006), and late infarction (arterial grafting to the left anterior descending coronary artery, p = 0.0006). Unadjusted survival after first infarct after coronary artery bypass grafting was 74% and 52% at 1 and 10 years; arterial grafting improved 10-year survival from 48% to 59% (p = 0.002). An additional benefit or cost of extending arterial grafting (n = 1,727) beyond a single one could not be identified (p > 0.1).

Conclusions. Arterial conduits, particularly to the left anterior descending coronary artery, should be used for coronary artery bypass grafting to reduce early and late myocardial infarction and its consequences. However, use of more than a single arterial graft appears to confer no additional benefit.

Coronary artery bypass grafting has evolved into abundant use of bilateral sequential mammary, radial, and gastroepiploic arteries. The assumption that single arterial grafting to the left anterior descending coronary artery (LAD) [1, 2] improved graft patency and late survival gave rise to the assumption that multiple arterial grafting would contribute further to superior results. However, after adjusting for differences in prevalence of risk factors, we [3] have been unable to identify an additional survival benefit of arterial grafts to other systems. This finding stimulated us to seek possible additional protection of multiple arterial grafting against the morbid event of myocardial infarction after coronary artery bypass grafting (CABG) and its consequences.

Material and methods

Patients
A consecutive series of 9,600 patients underwent isolated first time CABG at the Gasthuisberg University Hospital of the Katholieke Universiteit Leuven (K.U. Leuven) Belgium, from 1971 to 1992. The mean age of the patients increased from 48.9 ± 7 years in 1971 to 62.3 ± 8 years in 1991. Seventeen percent of the patients were women. Single coronary system disease was present in 11%, two-system disease in 29%, and three system disease in 60%. Left main coronary artery stenosis of more than 90% stenosis was identified in 355 patients. Mild mitral and aortic valve regurgitation, insufficient to warrant valvular reconstruction or replacement, was present in 643 and 95 patients, respectively.

The complete data set has been described and characterized in detail in previous publications [3].

Surgical technique
Intermittent aortic cross-clamping, moderate hypothermia at 28°C, and pretreatment with 1 mg/kg of lidoflazine [4] since 1980, have been the technique of choice for managing the ischemic myocardium during operation. Arterial grafting was started using the internal mammary artery (IMA) in 1972. At least one in-situ IMA anastomosis was constructed in 6,074 patients. Bilateral and sequential IMA [5] grafting started in 1973 and 1978, respectively, but the use and the method of use was inconsistent over time. The left IMA was constructed most frequently to the LAD system (n = 4,833 patients). Bilateral IMAs were constructed in 207 patients to a single coronary system and in 985 patients to two coronary systems. The distribution of the patients by in-situ IMA distal anastomoses and by age group is presented in Table 1. The number of patients alive, without having suffered an infarct after CABG, within various follow-up intervals, is presented according to the number of in-situ IMA distal anastomoses in Table 2. In addition to the in-situ IMA anastomoses, IMA free grafting and gastroepiploic artery in-situ grafting were performed in 122 and 43 patients, respectively. In-situ arterial grafting only was achieved in 1,088 patients, of which 442 had multiple system disease.


View this table:
[in this window]
[in a new window]
 
Table 1. Distribution of Patients by Number of In-Situ Internal Mammary Artery Distal Anastomoses and by Age at Operation (excluding the internal mammary artery free and gastroepiploic anastomoses)

 

View this table:
[in this window]
[in a new window]
 
Table 2. Number of Patients at Risk by Year After Operation (alive without having suffered a first infarct after coronary artery bypass grafting) and by Number of In-Situ Mammary Artery Distal Anastomoses

 
Follow-up
The K.U. Leuven Coronary Surgery Database has a core of regular, fully documented, follow-up reports by the referring specialists. These reports document each event, suspicion of event, or regular visit. In addition to these nonsystematic follow-up reports, a formal cross-sectional follow-up was undertaken in 1987 to 1988 and repeated between January 1993 and July 1994. The common closing date for outcome information was January 1, 1993. All information up to January 1, 1993, was included in the analysis. Follow-up was complete for 99.9% (11 had incomplete follow-up). Median follow-up for the survivors was 6.4 years (range, 30 days to 22 years); average follow-up was 7.07 ± 4.3 years.

Event
The diagnosis of early perioperative infarct was documented by the intensive care specialist (an independent unit) using repeated surface electrocardiogram (ECG) (Minnesota classification) and routine enzymatic measurements. The cut-off value for positive enzymes was a creatinine kinase MB fraction higher than 8% of total creatinine kinase. The diagnosis of later perioperative infarct was based on repeated routine in-house surface ECG and enzymatic measurements on suspicion of the event. The ECG changes were always compared with earlier ECGs of the patient before confirmation of the new event. Surface ECG by the referring cardiologist (an independent unit) at the first visit after CABG confirmed where appropriate the perioperative diagnosis.

The diagnosis of follow-up infarcts was documented by the attending cardiologist. If the ECG changes in follow-up did not correlate with clinical symptoms in the same time frame, the date and time of first occurrence of the ECG changes were considered the relevant date and time for the event. Patients not experiencing the event were censored at the common closing date, at the end of follow-up for those with incomplete follow-up, or at death, whichever occurred earliest.

Characterization of overall freedom from first infarct
Nonparametric estimates of overall nonrisk-adjusted freedom from first infarct were obtained by the method of Kaplan and Meier [6]. A completely parametric method was used to identify the number of hazard phases, identify the form of the equation for each phase, and estimate the parameters that characterize the distribution of times until first infarct [7].

Multivariable analysis of freedom from first infarct
The general methods used to identify incremental risk factors for first infarct have been described previously for the event death [3], including the variables (Appendix 1) and their organization for analysis, and the exploratory analyses accompanying the multivariable analyses, which were conducted in the parametric, multiphase hazard function domain.

In a directed stepwise entry of variables into the multivariable risk factor model, a p value criterion of 0.05 was used for retention of variables in the final analysis. Regression coefficients are presented plus or minus one standard error. Goodness of fit of the patient–procedure–experience model to the data was checked in the two ways previously detailed [8, 9].

Sequential analyses
To facilitate the analysis and better discover and understand the nature and influence of single and multiple arterial grafting in the face of change in prevalence of other variables, the risk factor analysis was conducted in a sequential fashion. First, only patient variables were entered, then procedure variables likely to be known or estimated at the time of decision making were added, including the use of arterial grafts, and finally experience variables. Variables from the isolated and preceding analyses were allowed to enter and leave the model.

Nature and influence of risk factors
Exploration of the influence of arterial grafting was performed by constructing a series of nomograms representing solutions of the final parametric equation for all variables (patient, procedure, and experience). These were risk-adjusted in the sense that all other variables in the model were set to those of a patient of median risk in the last year of the study. Thus, each figure represents the risk-adjusted prediction for a specific, but typical, hypothetical patient (Table 3).


View this table:
[in this window]
[in a new window]
 
Table 3. Patient Profile of the Median Patient Used for the Nomograms and Patient-Specific Predictions (unless specified differently in the appropriate legend)

 
Depictions
Graphic depictions in this article have been standardized as follows. Each event in the depiction of freedom from first infarct (Fig 1A) is represented by a circle positioned along the horizontal axis at the time of the infarct and on the vertical axis according to Kaplan-Meier lifetable estimates, enclosed at 2-year intervals between confidence limits equivalent to one standard error. The solid line is the parametric estimate of freedom from first infarct enclosed within dashed 70% confidence limits equivalent to one standard error. The numbers in parentheses represent the number of patients without the event and traced beyond that point. The solid line in the hazard function depiction (Fig 1B) is the parametric estimate of the hazard, enclosed within dashed 70% confidence limits equivalent to one standard error. The solid lines in the patient-specific predictions and nomograms represent specific solutions of the parametric equations, enclosed within dashed 70% confidence limits equivalent to one standard error.



View larger version (23K):
[in this window]
[in a new window]
 
Fig 1. (A) Parametric freedom from first infarct after primary isolated coronary artery bypass grafting (CABG) (n = 9,600). (B) Hazard function for first infarct at any time after primary isolated CABG (n = 9,600) (instantaneous risk at every point in time after the operation).

 
The solid lines in the nomograms for difference in predicted percentage freedom from first infarct represent the solutions of the parametric equations, enclosed within dashed 90% confidence limits.

Results

Nonrisk-adjusted freedom from first infarct
A first infarct after CABG was identified in 1,030 patients (the remaining 8,570 patients were censored at death, the common closing date or, rarely, at incomplete follow-up). The nonrisk adjusted 1-month, 1-, 10-, and 15-year freedom (Fig 1A) from first infarct was 97.3%, 96.7%, 86%, and 73%, respectively. A three-phase hazard function was identified (Fig 1B). It consists of an early hazard phase, corresponding to the perioperative period, that rapidly declined to disappearance by the fifth day after operation, a constant hazard phase and a late hazard phase rising gradually beyond 2 years after operation for as long as the extent of follow-up. Arterial grafting was associated with a lower prevalence of infarction after CABG (p < 0.0001) and this reduction was similar in magnitude for one, two, three, or four IMA distal anastomoses (p < 0.0001) for the full extent of their follow-up (Fig 2).



View larger version (26K):
[in this window]
[in a new window]
 
Fig 2. Actuarial freedom from infarct by number of in-situ mammary artery (IMA) distal anastomoses and uncorrected for any patient-related or other procedural variability. The patients without an arterial anastomosis are represented by circles, those with one arterial anastomosis by squares, those with two by triangles, and those with three by diamonds. (CABG = coronary artery bypass grafting.)

 
Risk-adjusted influence of arterial grafting on infarction after coronary artery bypass grafting
The reduction of risk of infarction after CABG by arterial grafting across time, from early to late, continued to be demonstrated after adjusting for other incremental risk factors (Table 4). Thus, perioperative infarction was reduced by arterial grafting (p = 0.005), as was infarction in general (constant hazard phase, p = 0.007). Risk was reduced in one-system disease even more than in multisystem disease (p = 0.006). The increasing prevalence of infarcts after the second year, accounting for most of the events after CABG, was reduced by use of arterial grafts to the LAD (p = 0.0006). Importantly, the benefit of arterial grafting persisted into older age in both multiple (Fig 3) and single-system disease.


View this table:
[in this window]
[in a new window]
 
Table 4. Incremental Risk Factors, Based on Patient, Procedure, and Institutional Variables, for Freedom From First Infarct After Primary Isolated Coronary Artery Bypass Graftinga

 


View larger version (26K):
[in this window]
[in a new window]
 
Fig 3. Nomogram for a median patient (see Table 4 for the patient-profile used) validating the difference in predicted percent freedom from first infarct after coronary artery bypass grafting (CABG) between one and no arterial anastomosis (preferably to the left anterior descending coronary artery) at 5, 10, and 15 years after CABG and for the whole spectrum of age at operation.

 
Neither benefit above that of simply using a single arterial graft, particularly to the LAD, nor increased risk, was demonstrated in the use of multiple arterial grafts (p > 0.1). However, before adjusting for other risk factors, apparent benefits of multiple grafting were found (Table 5), none of which persisted after risk adjustment.


View this table:
[in this window]
[in a new window]
 
Table 5. Univariate Non–Time-Related Comparison of the Number of Events Within the Follow-up Interval by Number of In-Situ Mammary Artery Distal Anastomosesa

 
Other risk factors for infarction after coronary artery bypass grafting
Perioperative myocardial infarction was strongly related to an unstable ST-segment, incomplete revascularization, and the practice of coronary endarterectomy (Table 4). Later infarcts were related to the aggressiveness and possible progression of atherosclerotic disease (vessel disease and history of peripheral and cerebral vascular disease), grade of diabetes, and higher cholesterol levels.

Events before and after first infarct
The first infarct was preceded by return of anginal symptoms in 386 patients (37%) of the total of the patients experiencing an infarct after CABG.

After the first infarct and within the follow-up interval after CABG, 400 of the 1,030 patients died. The nonrisk-adjusted parametric survival after first infarct after CABG at 1 month, 5 years, and 10 years was 79%, 65%, and 52%, respectively (Fig 4). Stratified by the presence of an arterial graft, but unadjusted for any residual variability, the 1-month and 10-year survival after first infarct was 77% and 48% without arterial grafting of any kind and 83% and 59% in the presence of an arterial graft (p = 0.002) (Fig 5). An additional benefit of multiple arterial grafting over a single arterial graft was not demonstrated (p = 0.6).



View larger version (23K):
[in this window]
[in a new window]
 
Fig 4. The actuarial survival and superimposed parametric function of survival after first infarct after coronary artery bypass grafting (CABG).

 


View larger version (30K):
[in this window]
[in a new window]
 
Fig 5. The actuarial survival after first infarct after coronary artery bypass grafting (CABG), stratified by the presence of an arterial graft at the primary procedure.

 
Return of angina after first infarct after CABG was observed in 499 patients. The non–risk-adjusted parametric freedom from angina after first infarct after CABG at 1 month and 10 years was 82% and 27% (Fig 6). A non–risk-adjusted benefit (p = 0.02) in return of angina after CABG was identified in favor of two in-situ IMA anastomoses versus none or only one (Fig 7). This difference was already active early after the infarct (77% versus 66% freedom from angina at 6 months) and increased with the extent of the follow-up (58% versus 40% freedom from angina at 5 years).



View larger version (25K):
[in this window]
[in a new window]
 
Fig 6. The actuarial freedom from angina and superimposed parametric function of freedom from angina after first infarct after coronary artery bypass grafting (CABG).

 


View larger version (27K):
[in this window]
[in a new window]
 
Fig 7. The actuarial freedom from angina after first infarct after coronary artery bypass grafting (CABG) stratified for 0 or 1 internal mammary artery (IMA) anastomosis versus more than 1 IMA anastomosis.

 
Reintervention for ischemic disease, cardiologic or cardiosurgical, after first infarct after CABG was observed in 250 patients. The non–risk-adjusted freedom from any reintervention after first infarct after CABG at 1 and 10 years was 79% and 63% (Fig 8). No benefit of either single or multiple (p = 0.3) arterial grafting was demonstrated.



View larger version (19K):
[in this window]
[in a new window]
 
Fig 8. The actuarial freedom from any cardiologic or cardiosurgical reintervention for ischemic disease after first infarct after coronary artery bypass grafting (CABG).

 
Comment

Limitations of the studied event
First infarct after CABG is nearly always a clinical event with electrocardiographic and often hemodynamic stigmata. The time relatedness of the event might be misdocumented over a few hours in the very early postoperative events, it might have been misdocumented over a few weeks in the rare silent late infarcts but the number of events will be reliable because the event will be identified at the next physician’s visit. Silent infarcts will nearly certainly have been missed in patients with left bundle-branch block.

Limitations of the data set
All statements related to arterial grafting are limited to the techniques of arterial grafting used during the time frame of the study reported. Sequential and bilateral in-situ IMA anastomoses were considered normal practice. A free IMA graft was only constructed when after planning in-situ grafting, the IMA was found to be too short or was damaged proximally. Only a limited number of patients with in-situ gastroepiploic grafting and none with radial artery grafting were performed during this time. Inferences about multiple arterial grafting are also limited by this technique being used more recently. However, even at 9 years of follow-up, more than 1,000 patients with multiple arterial grafts are alive without infarct, and at 10 years, more than 800.

Clinical relevance of the event for the patient
The clinical relevance of infarct after CABG is increased by the fact that few of the patients received anginal warnings of the impending infarct. The hazard function indicates that monitoring for early infarcts is advisable, with diminishing returns, for about 5 days after operation, and the risk of infarction must be weighted against the benefits of early discharge after CABG.

A higher prevalence, early and late, of infarct after CABG was reported in the Bypass Angioplasty Revascularization Investigation trial [10], 80.4% at 5 years. This higher prevalence could have been induced by the absence of single vessel disease, the smaller sample size (n = 914), the higher periprocedural infarct rate of 4.6% and the multicenter aspect of the trial. The results of our study are similar to the 10- (89% ± 2%) and 15-year (77% ± 3%) freedom given for a smaller group (n = 428) of patients but also with very extended and complete follow-up [11], using the anniversary method.

This study gives a first insight in several events after infarct. The first infarct after CABG has a 1-month lethal cost of close to 21% (Fig 2) (uncorrected for patient and procedure variability). This mortality is comparable to mortality after infarct without previous CABG, because it includes patients in all grades of cardiac failure at the moment of infarct. The 30-day mortality in the Gruppo Italiano per lo Studio della Streptochinase nel’Infarto miocardico 1 trial [12] increased from 7% for Killip class I to 81% for Killip class IV. Stratified actuarials explored the relation between some of the patient variability and survival after first infarct after CABG: age more than 65 years of age (p = 0.0007), insulin-treated diabetes (p = 0.0001), and ventricular function (p = 0.0001).

Even if the patient survives, quality of further life will be reduced by the loss of ventricular mass and function, concomitant with myocardial cell necrosis.

Return of angina was noted fairly rapidly in most patients after their first infarct after CABG. This high rate could have been induced by the use of thrombolysis, often reducing the impact of the infarct but not taking away the cause.

Impact of arterial grafting on freedom from first infarct
From the first reports by Kay [13] and Barner [14] and their colleagues emphasizing the good patency rates after direct anastomosis between an internal mammary artery graft and a coronary artery, surgeons have been increasing their expectation in this graft. This was further increased after Siegel and Loop [15] reported higher patency rates compared to saphenous vein grafts, certainly when this was correlated with improved survival [16]. Tector and coworkers [17] insisted in 1983 to use this arterial conduit for grafting the anterior descending coronary artery.

Several investigators reported reduced early postoperative infarction rates in the presence of arterial or more extensive arterial grafting, sometimes without [18], sometimes after correction [19, 20] for patient variability. These findings were confirmed in this study with the first-month reduction of freedom from infarct for the median patient from 97% to 98% by having at least one arterial graft, preferably to the LAD. The additional early benefit of increasing the number of arterial grafts above a single one was lost after correction for patient variability.

Loop and colleagues [1] demonstrated a better late cardiac event-free survival after a left IMA anastomosis, versus a saphenous vein, to the LAD. These findings are confirmed in this study for the event infarct, after correction for patient variability, and are quantified for a median patient (see Table 3) in Figure 3. This benefit is increasing over time and as far as the extent of the follow-up. An additional benefit is identified in the interaction between single vessel disease and the presence of only arterial grafts. This benefit is active over the entire follow-up interval but most visible between a few days and 2 years after operation, because this is the interval when the constant phase is proportionally the most important.

The positive findings for a single mammary artery graft prompted surgeons to use both arteries. In a case-matched study with a follow-up of 15 years, Fiore and colleagues [21] observed, a significant (p = 0.02) reduction (59% to 75% freedom) of late infarcts in increasing the number of mammary artery grafts to two. But the curves for both groups crossed one another at 10 years after operation. These findings were not reconfirmed in this study after correction for patient variability. A median patient (Table 3) improves freedom from infarct at 10 years from 86% to 91% by having one arterial graft, preferably to the LAD. A similar additional increase with a second arterial graft is very unlikely because it would annihilate all other influences. The absence of additional advantage of a second or third IMA anastomosis could have been foreseen as the first IMA anastomosis was most frequently selected for the supply of the left anterior descending artery, the dominant artery responsible for the preservation of the ventricular function and capable of delivery of collateral flow.

Impact of arterial grafting on events after first infarct after coronary artery bypass grafting
In addition to a first insight in the prevalence and time structure of events after-infarct, this study has explored the influence of arterial grafting on these events. An arterial graft protected the patient’s survival after the first infarct after CABG (Fig 5). No additional benefit of single arterial grafting was documented in return of postinfarct angina or reintervention. Double mammary artery reconstruction reduced return of angina after CABG (Fig 7), certainly versus a single or no arterial graft. Further research is warranted to determine whether these benefits remain active after adequate correction for some of the identified patient variability.

Clinical inferences
The first infarct after CABG is a rare event with major clinical relevance for the patient. Patients in whom the demographic, cardiac or noncardiac comorbidity reduces the 10-year survival are unlikely to suffer the event. Only one-third of the patients is warned by preinfarct angina. The occurrence of this first infarct after CABG should be avoided by all therapeutic and procedural means, as well during the primary CABG procedure as in follow-up.

Arterial grafting, certainly to the LAD, seems one of these therapeutic possibilities. No increased risk or benefit was identified with more extensive or complete arterial grafting in any hazard phase. The age of the median coronary bypass patient in 1998 has reached or exceeded 70 years in most surgical programs. The comorbidity has risen in parallel. Therefore, it is unlikely that more extensive arterial revascularization will ever reduce the prevalence of first infarct after CABG due to the rarity of the event, the limited life expectancy of the median patient, and the not yet identifiable benefit of this extensive arterial grafting.

Acknowledgments

We thank Robert Brown (UAB) for his unsurpassed expertise in handling the most complex database, analytic, and graphic requests.

Appendix 1: Variables considered in the multivariable analysis of infarct after coronary artery bypass grafting

Patient variables
Demographics. Sex; age (years) at operation; weight; height; body surface area; body mass index; weight–height ratio, difference and ratio of weight to ideal body weight where ideal weight is (height in cm minus 100) for men and (height in cm minus 110) for women; blood group; rhesus factor.

Preoperative rhythm disturbances. Atrial fibrillation; right hemiblock, left partial or total hemiblock (and either); recent ventricular tachycardia or ventricular fibrillation or intractable ventricular tachycardia or repeated ventricular fibrillation; permanent pacemaker implanted before or at the coronary artery bypass grafting.

Previous procedures. Percutaneous transluminal coronary angioplasty (PTCA) unsuccessful PTCA, successful PTCA, number of previous PTCAs, interval since last PTCA, duration of freedom from angina after last PTCA; previous noncarotid vascular operation, previous carotid endarterectomy, or either.

Acute myocardial infarction. Interval between infarct and operation; location of infarct (coronary distribution); use of preoperative thrombolytic therapy; interval since last thrombolytic therapy.

Hemodynamic status. Cardiogenic shock without or with cardiopulmonary resuscitation; hemodynamic instability (0 = stable, 1 = unstable on medication but not in shock, 2 = shock, 3 = shock with cardiopulmonary resuscitation; unstable (yes/no), and graded with states 2 and 3 combined); New York Heart Association class (limitation by either angina or heart failure); increment of limitation by heart failure above that of angina (0 = none, 1 = mild, 2 = moderate, 3 = severe).

Symptoms of reversible ischemia. K.U. Leuven Angina Class (0 = mild, 1 = mild symptoms, 2 = symptoms with normal activities, 3 = severe with symptoms even at rest, 4 = unstable angina); Canadian Angina Class (0–4, and augmented to grade 5 by unstable angina); duration of anginal symptoms; angina at rest; unstable angina; treatment requirement for unstable angina (0 = no unstable angina, 1 = unstable angina controlled by intravenous medication, 2 = changing ST segment in the hours before operation despite maximal intravenous medication.

Exercise testing. Positive exercise test by electrocardiogram or on clinical grounds, clinically positive test; electrocardiogram positive test.

Distribution of coronary artery disease (limited to those predictable at the time of decision making). Number of coronary systems diseased (70% diameter reduction or more), one, two, or three system disease, left main stenosis (percent, >=50%, >=70%, and >=90%).

Left ventricular function. Ejection fraction; left ventricular end-diastolic pressure; number of previous myocardial infarcts; left ventricular hypertrophy on electrocardiogram; graded (subjective) ventricular dysfunction (0 = none, 1 = mild, 2 = moderate, 3 = severe).

Coexisting conditions (cardiac). Ischemic mitral incompetence (insufficient to require surgical intervention); aortic valve stenosis; aortic valve insufficiency.

Coexisting vascular disease. Abdominal aortic disease; peripheral vascular disease; cerebral vascular disease; carotid artery disease; internal carotid artery occlusion, internal carotid artery percent stenosis; 80% to 99% uni- or bilateral internal carotid artery stenosis, previous history of vascular operation, previous history of carotid operation, history of stroke; history of transient ischemic attack, calcification of ascending aorta.

Hyperlipidemia. Cholesterol level; HDL level; low-density lipoprotein level; triglyceride level.

Coexisting conditions (noncardiac). Diabetes (graded as 0 = none, 1 = oral treatment, 2 = insulin treatment, and each grade separately); overweight (>10 kg above calculated ideal weight, based on sex and height as defined under demographic variables above); difference from ideal weight; ratio of actual weight versus ideal weight; hypertensive (systolic blood pressure >160 mm Hg or diastolic pressure >100 mm Hg, or on antihypertensive medication); current or history of malignancy; on dialysis; history of severe renal failure; history of renal transplantation; history of nephrectomy; history of hepatic disease (hepatitis or clinical hepatic dysfunction); history of smoking; family history of ischemic heart disease; pulmonary disease (legally confirmed incapacitating anthracosilicosis, important reduction in diffusing capacity, chronic obstructive pulmonary disease, asthmatic bronchitis), chronic obstructive pulmonary disease, pulmonary function (forced vital capacity volumes and 1-second expiratory volumes, these normalized to gender height and age); psychiatric history.

Procedure variables (limited to those predictable at the time of decision making)
Bypassing conduit. Use of saphenous vein conduits (solely or with other conduits), number of saphenous vein conduits used, number of vein graft distal anastomoses, location of coronary systems to which vein grafts are anastomosed; use of internal thoracic artery (solely or with other conduits); number of internal mammary artery arteries used; number of internal mammary artery distals; location and number of coronary systems receiving internal mammary artery conduits; gastroepiploic artery as the conduit; number of distals; and location of systems receiving this conduit; total arterial conduits, distals and location of anastomoses; end-to-end grafts used; prosthetic conduits used; free internal mammary artery used; ratio of total conduits to total distals, and by extent of coronary disease; ratio of arterial conduits to total arterial distals, and by extent of coronary disease; ratio of nonarterial conduits to total nonarterial distals, and by extent of coronary disease; the largest number of distals on an arterial graft, largest number of distals on a nonarterial graft; patch grafts used; completeness of revascularization.

Quality of distal vessels. Proportion of distal anastomoses to small coronary arteries (1 mm or less in size).

Concomitant procedures. Repair of abdominal aortic aneurysm; carotid endarterectomy; plication or resection of left ventricular aneurysm (limited anterior or apical).

Institutional experience variables
Each surgeon; inexperienced surgeons; surgeon’s experience (number of isolated coronary cases operated on previous to that patient); surgeon’s routine (number of isolated coronary cases operated on in the previous calendar year); date of operation (number of years since 1971); month of operation.

Appendix 2: Parameter estimates, selected variables, their mathematical transformation, their coefficients, and their standard error for the final model

Early phase
Intercept = 0.0006341649; Delta = 0; Rho = 0.003259097; Nu = 14.33759; M = 0

Height of the patient (inverse transformation, 170 divided by length in cm) = 5.477461 ± 1.45; Unstable ST-segment but not acute infarct = 0.4786189 ± 0.0946; Infarct within 30 days before operation = -0.946236; Preoperative inferior infarct = -0.639429 ± 0.413; History of peripheral vascular disease = 0.4065837 ± 0.163; Preoperative pulmonary vital capacity as a percent of normal = -0.858741 ± 0.426; Presence of an arterial graft = -0.336324 ± 0.120; Coronary endarterectomy performed = 1.672594 ± 0.160; Planned concomitant pacemaker insertion = 2.506339 ± 0.713; Incomplete revascularization = 0.4348333 ± 0.146; Low-risk-for-infarct-return surgeon = -0.804866 ± 0.158.

Constant phase
Intercept = 4.940636E-06

Height of the patient (inverse transformation, 170 divided by length in cm) = 6.483815 ± 2.99; Presence of an arterial graft = -0.636646 ± 0.236; Incomplete revascularization = 0.89658 ± 0.251; Age at operation (squared 50 divided by age at operation) = 0.9953316 ± 0.205; Stable angina before operation = -0.640694 ± 0.218; Clinical or electrocardiographical positive stress test before operation = -0.6967748 ± 0.280; Percent left main coronary artery stenosis = -1.78812 ± 0.840; Preoperative aortic valve incompetence = 1.50528 ± 0.504; Preoperative history of abdominal aortic disease = 1.193248 ± 0.356; Preoperative blood urea nitrogen higher than 50 mg/dL = 1.155435 ± 0.393; Presence of a patch graft = 2.338759 ± 0.591; One system disease and no arterial grafts constructed = 0.788195 ± 0.288.

Late phase
Intercept = 2.548915E-07; Tau = 1; Gamma = 2.591674; Alpha = 1; Eta = 1

Infarct within 30 days before operation = 0.7825094 ± 0.265; History of peripheral vascular disease = 0.5642084 ± 0.157; Preoperative pulmonary vital capacity as a percent of normal = -1.0873 ± 0.459; Height of the patient = 0.04568757 ± 0.0135; Blood group A = -0.285174 ± 0.112; Two or three coronary system disease = 0.7000357 ± 0.274; Cerebral (noncarotid) vessel disease = 1.232227 ± 0.404; Preoperative cholesterol value (inverse transformation) = -1.04798 ± 0.288355; Higher grade of diabetes (grade 0 = no diabetes; grade 1 = abnormal glucose tolerance test with dietary treatment; grade 2 = diabetic, receiving oral hypoglycemic treatment; grade 3 = insulin-treated diabetes) (the squared transformation is used) = 0.1184553 ± 0.0291; Nonarterial graft to the body of the left anterior descending coronary artery = 0.4023177 ± 0.117.

References

  1. Loop F.D., Lytle B.W., Cosgrove D.M., et al. Influence of the internal mammary artery graft on 10-year survival and other cardiac events. N Engl J Med 1986;314:1-6.[Abstract]
  2. Sergeant P.T., Lesaffre E., Flameng W., Suy R. Internal mammary artery: methods of use and their effect on survival after coronary bypass surgery. Eur J Cardiothorac Surg 1990;4:72-78.[Abstract]
  3. Sergeant P.T., Blackstone E.H., Meyns B., Leuven K.U. Coronary Surgery Program. Validation and interdependence with patient-variables of the influence of procedural variables on early and late survival after CABG. Eur J Cardiothorac Surg 1997;12:1-19.[Abstract]
  4. Flameng W., Borgers M., Van der Vusse G., et al. Cardioprotective effects of lidoflazine in extensive aorta–coronary bypass grafting. J Thorac Cardiovasc Surg 1983;92:758-768.
  5. Sergeant P., Flameng W., Suy R. Internal mammary artery jumpgraft. J Cardiovasc Surg 1988;29:596-600.[Medline]
  6. Kaplan E., Meier P. Non-parametric estimation from incomplete observations. J Am Stat Assoc 1958;53:457-481.
  7. Blackstone E.H., Naftel D., Turner M. The decomposition of time-varying hazards into phases, each incorporating a separate stream of concomitant information. J Am Stat Assoc 1986;81:615-624.
  8. Blackstone E.H., Kirklin J.W. Recommendations for prophylactic removal of heart valve prostheses. J Heart Valve Dis 1992;1:3-14.[Medline]
  9. Ferrazi P., McGiffin D.C., Kirklin J.W., et al. Have the results of mitral valve replacement improved?. J Thorac Cardiovasc Surg 1986;92:186-197.[Abstract]
  10. The Bypass Angioplasty Revascularisation Investigation (BARI) Investigators. Comparison of coronary bypass surgery with angioplasty in patients with multivessel disease. N Engl J Med 1996;335:275-277.[Free Full Text]
  11. Van Brussel B.L., Plokker H.W., Voors A.A., et al. Multivariate risk factor analysis of clinical outcome 15 years after venous coronary artery bypass graft surgery. Eur Heart J 1995;16:1200-1206.[Abstract/Free Full Text]
  12. Gruppo Italiano Per Lo Studio Della Streptochinasi Nell’Infarto Miocardico (GISSI). Effectiveness of intravenous thrombolytic treatment in acute myocardial infarction. Eur Heart J 1990;11(Suppl B):139-146.
  13. Kay E.B., Naraghipour H., Beg R.A., et al. Internal mammary artery bypass graft long-term patency rate and follow-up. Ann Thorac Surg 1974;18:269-279.[Medline]
  14. Barner H.B., Mudd J.G., Mark A.L., et al. Patency of internal mammary coronary grafts. Circulation 1976;54(Suppl):70-73.
  15. Siegel W., Loop F.D. Comparison of internal mammary artery and saphenous vein bypass grafts for myocardial revascularization: exercise test and angiographic correlation. Circulation 1976;54(Suppl 3):1-3.[Free Full Text]
  16. Loop F.D., Irarrazaval M.J., Bredee J.J., et al. Internal mammary artery graft for ischemic heart disease. Effect of revascularization on clinical status and survival. Am J Cardiol 1977;39:516-522.[Medline]
  17. Tector A.J., Schmahl T.M., Canino V.R. The internal mammary artery graft: the best choice for bypass of the diseased left anterior descending coronary artery. Circulation 1983;68(Suppl 2):214-217.
  18. Tector A.J., Kress D.C., Schmahl T.M., et al. T-graft: a new method of coronary arterial revascularization. J Cardiovasc Surg (Torino) 1994;35(6 Suppl 1):19-23.[Medline]
  19. Grover F.L., Johnson R.R., Marshall G., et al. Impact of mammary grafts on coronary bypass operative mortality and morbidity. Ann Thorac Surg 1994;57:559-569.[Abstract]
  20. Del Rizzo D.F., Fremes S.E., Christakis G.T., et al. Coronary bypass with arterial conduits. Cardiovasc Surg 1998;6:81-89.[Medline]
  21. Fiore A.C., Naunheim K.S., Dean P., et al. Results of internal thoracic artery grafting over 15 years: single versus double grafts. Ann Thorac Surg 1990;49:202-209.[Abstract]



This article has been cited by other articles:


Home page
Ann. Thorac. Surg.Home page
N. J.G.M. Veeger, G. F. Panday, A. A. Voors, J. G. Grandjean, J. van der Meer, and P. W. Boonstra
Excellent Long-Term Clinical Outcome After Coronary Artery Bypass Surgery Using Three Pedicled Arterial Grafts in Patients With Three-Vessel Disease
Ann. Thorac. Surg., February 1, 2008; 85(2): 508 - 512.
[Abstract] [Full Text] [PDF]


Home page
Card Surg AdultHome page
E. Gongora and T. M. Sundt III
Myocardial Revascularization with Cardiopulmonary Bypass
Card. Surg. Adult, January 1, 2008; 3(2008): 599 - 632.
[Full Text]


Home page
Ann. Thorac. Surg.Home page
M. Gaudino, N. Luciani, F. Glieca, C. Cellini, C. Pragliola, C. Trani, F. Burzotta, G. Schiavoni, A. Anselmi, and G. Possati
Patients with in-stent restenosis have an increased risk of mid-term venous graft failure.
Ann. Thorac. Surg., September 1, 2006; 82(3): 802 - 804.
[Abstract] [Full Text] [PDF]


Home page
J. Thorac. Cardiovasc. Surg.Home page
O. Ashraf
Redo coronary bypass grafting: Role of arterial grafts and time interval
J. Thorac. Cardiovasc. Surg., July 1, 2006; 132(1): 209 - 210.
[Full Text] [PDF]


Home page
J. Thorac. Cardiovasc. Surg.Home page
V. Guru, S. E. Fremes, and J. V. Tu
How many arterial grafts are enough? A population-based study of midterm outcomes
J. Thorac. Cardiovasc. Surg., May 1, 2006; 131(5): 1021 - 1028.
[Abstract] [Full Text] [PDF]


Home page
CirculationHome page
M. Gaudino, C. Cellini, C. Pragliola, C. Trani, F. Burzotta, G. Schiavoni, G. Nasso, and G. Possati
Arterial Versus Venous Bypass Grafts in Patients With In-Stent Restenosis
Circulation, August 30, 2005; 112(9_suppl): I-265 - I-269.
[Abstract] [Full Text] [PDF]


Home page
J. Thorac. Cardiovasc. Surg.Home page
L.M. Stevens, M. Carrier, L.P. Perrault, Y. Hebert, R. Cartier, D. Bouchard, A. Fortier, I. El-Hamamsy, and M. Pellerin
Single versus bilateral internal thoracic artery grafts with concomitant saphenous vein grafts for multivessel coronary artery bypass grafting: Effects on mortality and event-free survival
J. Thorac. Cardiovasc. Surg., May 1, 2004; 127(5): 1408 - 1415.
[Abstract] [Full Text] [PDF]


Home page
CirculationHome page
A. Zacharias, R. H. Habib, T. A. Schwann, C. J. Riordan, S. J. Durham, and A. Shah
Improved Survival With Radial Artery Versus Vein Conduits in Coronary Bypass Surgery With Left Internal Thoracic Artery to Left Anterior Descending Artery Grafting
Circulation, March 30, 2004; 109(12): 1489 - 1496.
[Abstract] [Full Text] [PDF]


Home page
J. Thorac. Cardiovasc. Surg.Home page
M. Caputo, B. Reeves, G. Marchetto, B. Mahesh, K. Lim, and G. D. Angelini
Radial versus right internal thoracic artery as a second arterial conduit for coronary surgery: early and midterm outcomes
J. Thorac. Cardiovasc. Surg., July 1, 2003; 126(1): 39 - 47.
[Abstract] [Full Text] [PDF]


Home page
Eur. J. Cardiothorac. Surg.Home page
G. G. Santos and N. A.G. Stolf
Reply to Hirose and Amano
Eur. J. Cardiothorac. Surg., December 1, 2002; 22(6): 1036 - 1036.
[Full Text] [PDF]


Home page
HeartHome page
P J Bradshaw, K Jamrozik, M Le, I Gilfillan, and P L Thompson
Mortality and recurrent cardiac events after coronary artery bypass graft: long term outcomes in a population study
Heart, December 1, 2002; 88(5): 488 - 494.
[Abstract] [Full Text] [PDF]


Home page
Eur. J. Cardiothorac. Surg.Home page
H. Corbineau, J.-P. Verhoye, T. Langanay, P. Menestret, and A. Leguerrier
Feasibility of the utilisation of the right internal thoracic artery in the transverse sinus in off pump coronary revascularisation: early angiographic results
Eur. J. Cardiothorac. Surg., November 1, 2001; 20(5): 918 - 922.
[Abstract] [Full Text] [PDF]


Home page
CirculationHome page
M. Endo, H. Nishida, Y. Tomizawa, and H. Kasanuki
Benefit of Bilateral Over Single Internal Mammary Artery Grafts for Multiple Coronary Artery Bypass Grafting
Circulation, October 30, 2001; 104(18): 2164 - 2170.
[Abstract] [Full Text] [PDF]


Home page
SEMIN CARDIOTHORAC VASC ANESTHHome page
N. J. Skubas and G. J. Despotis
Optimal Management of Bleeding Complications After Cardiac Surgery
Seminars in Cardiothoracic and Vascular Anesthesia, September 1, 2001; 5(3): 217 - 228.
[Abstract] [PDF]


Home page
Ann. Thorac. Surg.Home page
P. A. Kurlansky, E. A. Traad, D. L. Galbut, M. Zucker, and G. Ebra
Efficacy of single versus bilateral internal mammary artery grafting in women: a long-term study
Ann. Thorac. Surg., June 1, 2001; 71(6): 1949 - 1958.
[Abstract] [Full Text] [PDF]


Home page
Eur. J. Cardiothorac. Surg.Home page
J. Tatoulis, B. F. Buxton, and J. A. Fuller
The radial artery in coronary re-operations
Eur. J. Cardiothorac. Surg., March 1, 2001; 19(3): 266 - 273.
[Abstract] [Full Text] [PDF]


Home page
J. Thorac. Cardiovasc. Surg.Home page
W. Stooker, H. W. M. Niessen, A. Baidoshvili, W. R. Wildevuur, V. W. M. Van Hinsbergh, J. Fritz, C. R. H. Wildevuur, and L. Eijsman
Perivenous support reduces early changes in human vein grafts: Studies in whole blood perfused human vein segments
J. Thorac. Cardiovasc. Surg., February 1, 2001; 121(2): 0290 - 297.
[Abstract] [Full Text] [PDF]


Home page
Eur. J. Cardiothorac. Surg.Home page
S. Bjessmo, N. Hammar, E. Sandberg, and T. Ivert
Reduced risk of coronary artery bypass surgery for unstable angina during a 6-year period
Eur. J. Cardiothorac. Surg., October 1, 2000; 18(4): 388 - 392.
[Abstract] [Full Text] [PDF]


Home page
Ann. Thorac. Surg.Home page
A. M. Lincoff, L. A. LeNarz, G. J. Despotis, P. K. Smith, J. E. Booth, R. E. Raymond, S. K. Sapp, C. F. Cabot, J. E. Tcheng, R. M. Califf, et al.
Abciximab and bleeding during coronary surgery: results from the EPILOG and EPISTENT trials
Ann. Thorac. Surg., August 1, 2000; 70(2): 516 - 526.
[Abstract] [Full Text] [PDF]


Home page
J. Thorac. Cardiovasc. Surg.Home page
M. Kawasuji, N. Sakakibara, S. Fujii, T. Yasuda, and Y. Watanabe
Coronary artery bypass surgery with arterial grafts in familial hypercholesterolemia
J. Thorac. Cardiovasc. Surg., May 1, 2000; 119(5): 1008 - 1013.
[Abstract] [Full Text] [PDF]


Home page
Eur. J. Cardiothorac. Surg.Home page
R. Dion, D. Glineur, D. Derouck, R. Verhelst, P. Noirhomme, G. El Khoury, E. Degrave, and C. Hanet
Long-term clinical and angiographic follow-up of sequential internal thoracic artery grafting
Eur. J. Cardiothorac. Surg., April 1, 2000; 17(4): 407 - 414.
[Abstract] [Full Text] [PDF]


Home page
Ann. Thorac. Surg.Home page
J. Tatoulis, B. F. Buxton, J. A. Fuller, and A. G. Royse
Total arterial coronary revascularization: techniques and results in 3,220 patients
Ann. Thorac. Surg., December 1, 1999; 68(6): 2093 - 2099.
[Abstract] [Full Text] [PDF]


Home page
J. Thorac. Cardiovasc. Surg.Home page
O. Wendler, B. Hennen, T. Markwirth, J. Konig, D. Tscholl, Q. Huang, E. Shahangi, H.-J. Schafers, and S. H. G. Borst
T GRAFTS WITH THE RIGHT INTERNAL THORACIC ARTERY TO LEFT INTERNAL THORACIC ARTERY VERSUS THE LEFT INTERNAL THORACIC ARTERY AND RADIAL ARTERY: FLOW DYNAMICS IN THE INTERNAL THORACIC ARTERY MAIN STEM
J. Thorac. Cardiovasc. Surg., November 1, 1999; 118(5): 841 - 848.
[Abstract] [Full Text] [PDF]


Home page
Ann. Thorac. Surg.Home page
T. M. Sundt III, H. B. Barner, C. J. Camillo, and W. A. Gay Jr
Total arterial revascularization with an internal thoracic artery and radial artery T graft
Ann. Thorac. Surg., August 1, 1999; 68(2): 399 - 404.
[Abstract] [Full Text] [PDF]


Home page
Ann. Thorac. Surg.Home page
S. Noda and H. B. Barner
Arterial conduits
Ann. Thorac. Surg., January 1, 1999; 67(1): 285 - 286.
[Full Text] [PDF]


Home page
Eur. J. Cardiothorac. Surg.Home page
F. D. Loop
Coronary artery surgery: the end of the beginning
Eur. J. Cardiothorac. Surg., December 1, 1998; 14(6): 554 - 571.
[Abstract]