Coronary bypass for stable angina: a prospective randomized study

Coronary artery bypass grafting versus medical therapy in patients with stable coronary artery disease: An individual patient data pooled meta-analysis of randomized trials

OBJECTIVES

It is unclear whether coronary artery bypass grafting (CABG) improves survival compared with medical therapy (MT) in patients with stable coronary artery disease (CAD). The aim of this analysis was to perform an individual-patient data-pooled meta-analysis of contemporary randomized controlled trials that compared CABG and MT in patients with stable CAD.

METHODS

A systematic search was performed in January 2021 to identify randomized controlled trials enrolling adult patients with stable CAD, randomized to CABG or MT. Only trials using at least aspirin, beta-blockers, and statins in the MT arm were included. Individual patient data were obtained from all eligible studies and pooled. The primary outcome was all-cause mortality.

RESULTS

Four trials involving 2523 patients (1261 CABG; 1262 MT) were included with a median follow-up of 5.6 (4.0-9.2) years. CABG was associated with increased risk of all-cause mortality within 30 days (hazard ratio [HR], 4.81; 95% confidence interval [CI], 1.95-11.83) but subsequent reduction in the long-term risk of death (HR, 0.79; 95% CI, 0.69-0.89). As such, the cumulative 10-year mortality rate was lower in patients treated with CABG compared with MT (45.1% vs 51.7%, respectively; odds ratio, 0.70; 95% CI, 0.58-0.85). Age and race were significant treatment effect modifier (interaction P = .003 for both).

CONCLUSIONS

In patients with stable CAD, initial allocation to CABG was associated with greater periprocedural risk of death but improved long-term survival compared with MT. The survival advantage for CABG became significant after the fourth postoperative year and was particularly pronounced in younger and non-White patients.

Coronary Revascularization and Long-Term Survivorship in Chronic Coronary Syndrome

Ischemic heart disease (IHD) persists as the leading cause of death in the Western world. In recent decades, great headway has been made in reducing mortality due to IHD, based around secondary prevention. The advent of coronary revascularization techniques, first coronary artery bypass grafting (CABG) surgery in the 1960s and then percutaneous coronary intervention (PCI) in the 1970s, has represented one of the major breakthroughs in medicine during the last century. The benefit provided by these techniques, especially PCI, has been crucial in lowering mortality rates in acute coronary syndrome (ACS). However, in the setting where IHD is most prevalent, namely chronic coronary syndrome (CCS), the increase in life expectancy provided by coronary revascularization is controversial. Over more than 40 years, several clinical trials have been carried out comparing optimal medical treatment (OMT) alone with a strategy of routine coronary revascularization on top of OMT. Beyond a certain degree of symptomatic improvement and lower incidence of minor events, routine invasive management has not demonstrated a convincing effect in terms of reducing mortality in CCS. Based on the accumulated evidence more than half a century after the first revascularization procedures were used, invasive management should be considered in those patients with uncontrolled symptoms despite OMT or high-risk features related to left ventricular function, coronary anatomy, or functional assessment, taking into account the patient expectations and preferences.

Coronary Artery Bypass Surgery in Peritoneal Dialysis Patients

Over the last two years, in the Toronto Western Hospital, five chronic renal failure patients suffering from severe symptomatic ischemic heart disease, who had been maintained on peritoneal dialysis underwent coronary artery bypass surgery. One of the five had simultaneous mitral valve replacement. Of the five, four survived with substantial improvement in symptoms, the fifth died soon after the operation. This paper describes the management of these patients and the dialysis technique used in the preand postoperative periods.

Coronary artery bypass surgery (CABG) is effective in the treatment of symptoms of ischemic heart disease and under some circumstances it seems to improve life expectancy (1–4). Cardiovascular disease, which frequently is associated with chronic renal failure (CRF) remains the most common cause of death in dialysis patients (5, 6). Several workers have reported successful cardiac surgery in hemodialysis patients (7–10); however, we know of no relevant literature on similar operations in those maintained on peritoneal dialysis. During the last 5 years there has been a considerable increase in the number of CRF patients receiving peritoneal dialysis (11), and this paper describes five of our patients who underwent bypass operations while maintained on this fonn of therapy.

Coronary artery bypass grafting: Part 1--the evolution over the first 50 years

Surgical treatment for angina pectoris was first proposed in 1899. Decades of experimental surgery for coronary artery disease finally led to the introduction of coronary artery bypass grafting (CABG) in 1964. Now that we are approaching 50 years of CABG experience, it is appropriate to summarize the advancement of CABG into a procedure that is safe and efficient. This review provides a historical recapitulation of experimental surgery, the evolution of the surgical techniques and the utilization of CABG. Furthermore, data on contemporary clinical outcomes are discussed.

Role of surgical revascularization in diabetic patients with coronary artery disease

Diabetes is a well-known risk factor for morbidity and mortality associated with coronary artery disease. Currently, diabetics represent approximately a quarter of patients requiring coronary revascularization in the USA. The purpose of this article is to review and analyze the available data in surgical revascularization of diabetic patients with coronary artery disease. The review will also examine new developments in myocardial revascularization and assess their probable impact on the long-term outcome of diabetic patients.

Revascularization of left main coronary artery disease

Coronary artery disease with left main stenosis is associated with the highest mortality of any coronary lesion. Studies in the 1970s and 1980s comparing coronary artery bypass grafting (CABG) and medical therapy showed a significant survival benefit with revascularization. In the angioplasty era, initial experience with percutaneous intervention was associated with poor clinical outcomes. As a result, percutaneous coronary intervention (PCI) was restricted to patients who were considered inoperable, or those with prior CABG with a functional graft to the left anterior descending or circumflex artery ("protected left main disease"). With the introduction of drug-eluting stents, there are new studies demonstrating comparable survival in patients who were revascularized using PCI and CABG, although percutaneous revascularization is associated with a higher rate of repeat revascularization. In the SYNTAX (Synergy between PCI with Taxus and Cardiac Surgery) trial, the combined incidence of death, myocardial infarction, and stroke was similar between the CABG and PCI groups; however, the stroke rate was higher in the CABG group. The degree and extent of disease as defined by the SYNTAX scoring system has allowed for stratification of risk and improved assignment of patients with left main stenosis to either PCI or CABG.

The impact of revascularization on mortality in patients with nonacute coronary artery disease

BACKGROUND

Although early revascularization improves outcomes for patients with acute coronary syndromes, the role of revascularization for patients with nonacute coronary artery disease is controversial. The objective of this meta-analysis was to compare surgical or percutaneous revascularization with medical therapy alone to determine the impact of revascularization on death and nonfatal myocardial infarction in patients with coronary artery disease.

METHODS

The Medline and Cochrane Central Register of Controlled Trials databases were searched to identify randomized trials of coronary revascularization (either surgical or percutaneous) versus medical therapy alone in patients with nonacute coronary disease reporting the individual outcomes of death or nonfatal myocardial infarction reported at a minimum follow-up of 1 year. A random effects model was used to calculate odds ratios (OR) for the 2 prespecified outcomes.

RESULTS

Twenty-eight studies published from 1977 to 2007 were identified for inclusion in the analysis; the revascularization modality was percutaneous coronary intervention in 17 studies, coronary bypass grafting in 6 studies, and either strategy in 5 studies. Follow-up ranged from 1 to 10 years with a median of 3 years. The 28 trials enrolled 13,121 patients, of whom 6476 were randomized to revascularization and 6645 were randomized to medical therapy alone. The OR for revascularization versus medical therapy for mortality was 0.74 (95% confidence interval [CI], 0.63-0.88). A stratified analysis according to revascularization mode revealed both bypass grafting (OR 0.62; 95% CI, 0.50-0.77) and percutaneous intervention (OR 0.82; 95% CI, 0.68-0.99) to be superior to medical therapy with respect to mortality. Revascularization was not associated with a significant reduction in nonfatal myocardial infarction compared with medical therapy (OR 0.91; 95% CI, 0.72-1.15).

CONCLUSION

Revascularization by coronary bypass surgery or percutaneous intervention in conjunction with medical therapy in patients with nonacute coronary artery disease is associated with significantly improved survival compared with medical therapy alone.

Use of cardiovascular medical therapy among patients undergoing coronary artery bypass graft surgery: results from the ROSETTA-CABG registry

INTRODUCTION

Secondary prevention is needed following coronary artery bypass graft (CABG) surgery to reduce the subsequent risk of unstable angina, myocardial infarction and death. However, little research exists on the use of cardiovascular medical therapy in CABG surgery patients. The objective of the present study is to describe the use of cardiovascular medical therapy among patients discharged after CABG surgery.

METHODS

The use of acetylsalicylic acid, clopidogrel, warfarin, antilipid agents, beta-blockers, calcium channel blockers, nitrates and angiotensin-converting enzyme (ACE) inhibitors was examined among 320 patients enrolled in the Routine versus Selective Exercise Treadmill Testing After Coronary Artery Bypass Graft Surgery (ROSETTA-CABG) Registry. Logistic regression identified the determinants of medication use at 12 months following CABG surgery.

RESULTS

Most patients were male, hyperlipidemic and underwent CABG surgery for relief of angina symptoms. At admission, discharge and at 12 months, acetylsalicylic acid was used in 71%, 92% and 87% of cases, respectively, and some form of antiplatelet agent was used in 74%, 94% and 89% of cases, respectively. The use of antilipid agents remained constant, from 55% at admission to 57% at discharge. However, 24% of patients were not receiving antilipid agents at 12 months. The use of beta-blockers was 57% at admission, 71% at discharge and 64% at 12 months. The use of calcium channel blockers and nitrates decreased modestly from admission to discharge and remained stable at approximately 20% and 22%, respectively, at 12 months. ACE inhibitor use remained stable, from 33% at admission to 38% at 12-months. Hyperlipidemia, hypertension, obesity and pre-CABG surgery left ventricular ejection fraction less than 40% were all found to be important determinants of 12-month medication use. Importantly, the use at discharge was an important determinant of 12-month use of for each medication examined in the present study.

CONCLUSIONS

The use of antilipid agents, beta-blockers and ACE inhibitors was found to be too low among post-CABG surgery patients, who are known to benefit from their use, and the use of nitrates was too high. Discharge from hospital provides a unique opportunity for physicians to modify the use of cardiovascular medical therapy among patients undergoing CABG surgery.

Cardiac medical therapy in patients after undergoing coronary artery bypass graft surgery

The purpose of this paper is to review the randomized controlled trial (RCT) data investigating cardiac medical therapy for patients after coronary artery bypass grafting (CABG). We identified RCTs with > or =100 enrolled patients that examined the impact of cardiac medical therapy on outcomes > or =1 year after CABG. The MEDLINE database was searched for trials conducted between 1966 and 2004 on the following medications: aspirin, antilipid agents, beta-blockers, calcium channel blockers (CCBs), nitrates, and angiotensin-converting enzyme (ACE) inhibitors. Both aspirin and antilipid agents were found to reduce the progression of atherosclerosis and the occurrence of graft occlusion. Cardiovascular events were decreased with antilipid agents. In small trials, beta-blockers and CCBs failed to decrease the incidence of cardiovascular events. No RCTs examined nitrates, and one small RCT documented a reduction in cardiovascular events among patients treated with ACE inhibitors. We conclude that few RCTs have examined the efficacy of cardiac medical therapy in post-CABG patients. Based on current RCT evidence, aspirin and antilipid agents should be used routinely after CABG. However, current data do not support the use of beta-blockers, CCBs, and nitrates, and more evidence is needed regarding the use of ACE inhibitors.

Understanding and treating vein graft atherosclerosis

BACKGROUND

Vein grafts have been used as bypass conduits for coronary artery disease since the 1960s. This widely used treatment, however, is complicated by the development of changes in the vein graft, which resemble atherosclerosis and are often termed as such. They occur at about 10 years, which leads to the need for reoperation in some patients. The purpose of this review is to summarize the knowledge regarding the pathophysiology of vein graft "atherosclerosis," as well as promising new treatments for this disease.

METHODS

The relevant literature relating to the epidemiology, histology, cell and molecular pathophysiology and treatment of vein graft atherosclerosis is reviewed.

RESULTS

The development of vein graft atherosclerosis differs from arterial atherosclerosis. Studies have examined the role of trauma, lipids, vasoactive mediators, smooth muscle cell mitogens, smooth muscle cells apoptosis, adhesion molecules and proteases. Therapies have been developed to prevent vein graft atherosclerosis based on these studies and have been tested using animal models and in patients.

DISCUSSION

Promising new therapies have been developed based on current knowledge and further applications of genomics will allow for the further identification of risk factors and mechanistic insights. The use of arterial grafts such as the internal mammary artery, which have higher patency rates at 10 years compared with vein grafts as well as approaches to revascularize infarcted myocardium may one day replace the use of vascular conduits.

Effect of coronary artery bypass graft surgery on survival: overview of 10-year results from randomised trials by the Coronary Artery Bypass Graft Surgery Trialists Collaboration

We carried out a systematic overview using individual patient data from the seven randomised trials that have compared a strategy of initial coronary artery bypass graft (CABG) surgery with one of initial medical therapy to assess the effects on mortality in patients with stable coronary heart disease (stable angina not severe enough to necessitate surgery on grounds of symptoms alone, or myocardial infarction). 1324 patients were assigned CABG surgery and 1325 medical management between 1972 and 1984. The proportion of patients in the medical treatment group who had undergone CABG surgery was 25% at 5 years, 33% at 7 years, and 41% at 10 years: 93.7% of patients assigned to the surgery group underwent CABG surgery. The CABG group had significantly lower mortality than the medical treatment group at 5 years (10.2 vs 15.8%; odds ratio 0.61 [95% CI 0.48-0.77], p = 0.0001), 7 years (15.8 vs 21.7%; 0.68 [0.56-0.83], p < 0.001), and 10 years (26.4 vs 30.5%; 0.83 [0.70-0.98]; p = 0.03). The risk reduction was greater in patients with left main artery disease than in those with disease in three vessels or one or two vessels (odds ratios at 5 years 0.32, 0.58, and 0.77, respectively). Although relative risk reductions in subgroups defined by other baseline characteristics were similar, the absolute benefits of CABG surgery were most pronounced in patients in the highest risk categories. This effect was most evident when several prognostically important clinical and angiographic risk factors were integrated to stratify patients by risk levels and the extension of survival at 10 years was examined (change in survival -1.1 [SE 3.1] months in low-risk group, 5.0 [4.2] months in moderate-risk group, and 8.8 [5.4] months in high-risk group; p for trend < 0.003). A strategy of initial CABG surgery is associated with lower mortality than one of medical management with delayed surgery if necessary, especially in high-risk and medium-risk patients with stable coronary heart disease. In low-risk patients, the limited data show a non-significant trend towards greater mortality with CABG.

Effect of coronary bypass surgery on anaerobic myocardial lactate metabolism during pacing-induced angina pectoris

Myocardial lactate metabolism was studied by coronary sinus catheterization in nine patients before and 8-12 months after coronary bypass surgery. Measurements were performed at rest and during atrial pacing increased to a heart rate which produced strong chest pain. The estimation of myocardial lactate extraction and release was facilitated by a constant rate infusion of 14C lactate and coronary sinus blood flow (CSBF) was measured by thermodilution. Pre-operatively strong chest pain could be elicited in all patients and isotope data indicated a significant myocardial lactate release in all of them, although the net a-cs difference was negative in only half of them. After bypass surgery the maximum tolerable heart rate was increased by 23 beats min-1 and chest pain both at heart rate 110 beats min-1 and at the highest heart rate achieved was reduced or absent in eight of the nine patients. The increase in chest pain during pacing was quantitatively related to the increase in myocardial lactate release, and the correlation between these two variables followed the same course after the operation as it did before. It is concluded that the improvement in chest pain limited cardiac performance after bypass surgery is well correlated with the improvement in myocardial aerobic metabolism.

Selection and evaluation of empirical research in technology assessment

Technology assessment involves application of the scientific method to the practice of medicine. Finding all of the assessment reports in a given field is not an easy task. Proper evaluation of those assessments requires the conduct of a prospective experiment in which the sources and results are blinded when the choice is made of papers to exclude and to include, and the process should be carried out in duplicate. There are several available data bases for carrying out the search, but because of indexing problems they should be supplemented by reference to the bibliographies of pertinent published articles. Clinical trials included in meta-analyses should be graded by quality and thus facilitate sensitivity analyses. Attention must be paid to the possibility of publication bias. Finally, the advent of meta-analysis makes it desirable to begin randomized controlled trials in areas of uncertainty, even when there is no possibility that individual investigators will encounter enough patients to draw valid conclusions.

Percutaneous transluminal coronary angioplasty of one vessel for refractory unstable angina pectoris: efficacy in single and multivessel disease

Forty patients with unstable angina refractory to medical treatment had one vessel percutaneous transluminal angioplasty to the most stenotic lesion in a major coronary artery. The procedure was successful in 35 patients, and the remaining five patients underwent emergency coronary artery bypass graft surgery. The initial success rate (84%) for the 16 patients with single or the 19 patients with multivessel disease (90%) was similar. At early follow up (average nine days) all patients with successful angioplasty remained symptomatically improved; 10 patients (83%) with single and 10 patients (63%) with multivessel disease had negative treadmill stress tests. Five of six cardiac events occurred within the intermediate (average 11 months) follow up period; two patients had recurrent refractory unstable angina, two had angioplasty for progression of disease in a vessel not previously treated by angioplasty, and one had bypass graft surgery. During late (average 26 months) follow up one patient had a non-fatal myocardial infarction while seven patients (58%) with single vessel disease and nine patients (75%) with multivessel disease had negative stress tests; 29 of 40 patients showed long term improvement.

Effect of aortocoronary bypass surgery on coronary circulation and myocardial metabolism during atrial pacing

Eleven patients with coronary heart disease, in whom at least one of several bypass grafts to the left coronary artery was patent, were selected for the study. The hemodynamics, coronary sinus blood flow, myocardial oxygen consumption, and myocardial lactate metabolism were evaluated at rest and during atrial pacing stress test before and after surgery. There were no significant improvements in the cardiac index, pulmonary arterial end-diastolic pressure, and left ventricular ejection fraction after aortocoronary bypass surgery. However, significant improvement of coronary sinus blood flow, myocardial oxygen consumption, and myocardial lactate extraction and consumption were found during postoperative atrial pacing compared with the preoperative findings. These results suggest that successful bypass grafting may improve myocardial lactate metabolism in ischemic lesions and contribute to the postoperative relief of angina.

Ten year survival after coronary artery bypass surgery for angina in patients aged 65 years and older

We have assessed the long-term results of coronary bypass surgery for angina from 1974 to 1983 in 1304 patients aged 65 years and older (group 1). Using actuarial techniques, we determined that the 5 year and 10 year survival rates for patients 65 years old or older were 81 +/- 2% and 65 +/- 3% (mean +/- SE), respectively. The patients aged 65 years and older were further subdivided into those aged 65 to 74 years (group 1a) and 75 to 84 years (group 1b) and were compared with 1700 patients aged 55 to 64 years (group 2). The operative mortality in the three subgroups was 3%, 3%, and 2%, respectively (p = NS). For coronary bypass surgery, the duration of hospital stay was significantly longer (p less than .0001) by a mean of 1 to 2 days for group 1 patients and the cost of hospitalization was higher by a mean of $ 700 (p = .25). The cost of hospitalization was significantly higher only for group 1b patients (p = .005). The 5 year survival rates for the three subgroups (1a, 1b, and 2) were 83 +/- 2%, 73 +/- 5%, and 91 +/- 1%, respectively, and the 10 year survival rates were 66 +/- 3%, 65 +/- 7% (7 year rate for subgroup 1b), and 77 +/- 2%, respectively. The lower survival rates for subgroups 1a and 1b were significant (p less than .001); however, this lower survival was only seen in men.(ABSTRACT TRUNCATED AT 250 WORDS)

Sustained efficacy of percutaneous transluminal coronary angioplasty

To determine whether the immediate efficacy of percutaneous transluminal coronary angioplasty (PTCA) is sustained, follow-up data were obtained in 183 patients who had undergone PTCA at least 1 year earlier. The duration of follow-up ranged from 1 to 5 years. Subjective clinical information was obtained in each patient and objective functional information, determined by exercise stress testing, was obtained in 91. PTCA was initially successful in 141 patients (79%). Of the 42 patients in whom PTCA was unsuccessful, 26 underwent coronary artery bypass graft surgery (CABG), while 16 were maintained on medical therapy (MED). When compared to the MED patients at time of follow-up, successful PTCA patients experienced less angina (13% vs 47%; p = 0.003), used less nitroglycerin (25% vs 73%, p = 0.003), were hospitalized less often for chest pain (8% vs 31%; p = 0.02), and subjectively felt their condition had improved (96% vs 20%; p less than 0.001). Furthermore, during exercise testing, the prevalence of angina was reduced (9% vs 43%; p = 0.05), and exercise duration was greater (8.2 minutes vs 5.8 minutes, p = 0.05) among PTCA patients. There were no significant differences in the incidence of subsequent myocardial infarction, mortality, or need for coronary artery bypass surgery. For these variables, no differences were seen between the CABG and PTCA groups. Thus, successful PTCA results in long-term relief of subjective and objective manifestations of myocardial ischemia, superior to that of medical therapy and comparable to CABG.

Comparative long-term effects of coronary artery bypass graft surgery and percutaneous transluminal coronary angioplasty on regional coronary flow reserve

To evaluate the relative long-term improvement in coronary artery hemodynamics after revascularization by coronary artery bypass graft surgery (CABG) or percutaneous transluminal coronary angioplasty (PTCA), regional coronary flow reserve (CFR) was measured, by digital computer analysis of 35 mm cine film, in 50 men undergoing cardiac catheterization. CFR (mean +/- SEM) in 12 atherosclerotic arteries before revascularization was 1.02 +/- 0.05. Mean CFR in 29 normal arteries of men with normal coronary arteriograms was significantly higher (2.59 +/- 0.11) than that in 16 atherosclerotic arteries of patients revascularized by CABG (2.02 +/- 0.17, p less than .01) or in 14 atherosclerotic arteries of those revascularized by PTCA (1.97 +/- 0.12, p less than .01). No difference in CFR between the CABG and PTCA groups was found and variables known to influence CFR were similar between groups. Equivalent and significant long-term improvement in coronary artery hemodynamics is provided by CABG or PTCA. We postulate that the difference in CFR in the men with normal arteries and those who underwent revascularization was related to the effects of the general atherosclerotic process, which remain despite successful treatment by these techniques.

Surgical survival in the Coronary Artery Surgery Study (CASS) registry

The overall surgical survival data in the Coronary Artery Surgery Study (CASS) registry have not been published to date, pending the report of the randomized medical-surgical comparison (CASS randomized trial). Non-randomized surgical survival data from the CASS registry are given in this article. The overall medical survival data from the registry were reported previously as a natural history study. There were 8,991 patients in the registry portion of CASS who had primary isolated coronary artery bypass grafting and 8,971 with follow-up of more than 30 days. The 5-year survival for all 8,971 patients was 90%, and the operative mortality was 2.37%. Patients with left main coronary artery disease had an operative mortality of 3.84% and a 5-year survival of 85%, while patients with lesions in other vessels had an operative mortality of 2.12% and a 5-year survival of 91%. Among patients without left main coronary disease, the 5-year survival was 93% in those with single-vessel and 92% in those with double-vessel disease (operative mortality was 1.50% and 1.92%, respectively) and 88% in patients with triple-vessel disease (operative mortality was 2.62%; p = 0.009). When results for patients with left main coronary artery obstruction were compared with those for triple-vessel disease, the 5-year survival figures were 85% and 88%, respectively (p = 0.02) and the operative mortality, 3.84% and 2.62%, respectively (p = 0.03). Patients with normal or nearly normal left ventricular (LV) function (i.e., LV segmental wall motion scores ranging from 5 through 11) had a 5-year survival of 92% and an operative mortality of 1.97%. Patients with moderate impairment (LV score range, 12 through 16) had a 5-year survival of 80% and an operative mortality of 4.21%. In those with poor ventricular function (LV score of 17 or greater), the 5-year survival was 65% and the operative mortality was 6.21%. The difference in survival among the three groups was significant (p less than 0.0001). Of 29 variables used in a stepwise Cox regression analysis, LV wall motion score, congestive heart failure score, age, number of operable vessels, smoking history, LV end-diastolic pressure, and percent of left main coronary artery stenosis were found to have a significant effect on long-term survival (excluding 30-day mortality), and these variables plus surgical priority and height influenced surgical mortality. When height was used in the Cox proportional hazards model, female sex was no longer a significant variable.

Myocardial infarction and mortality in the coronary artery surgery study (CASS) randomized trial

The long-term benefit of coronary bypass surgery in terms of longevity and prevention of major ischemic events in patients who have mild angina is not well defined. The randomized Coronary Artery Surgery Study (CASS) was designed to evaluate this issue; it consists of 780 patients who were considered operable and who had mild stable angina pectoris or who were free of angina after infarction. As a result of the randomization process there were no significant differences in base-line variables between patients randomly assigned to medical and to surgical therapy. The likelihood of death in the five-year period after randomization was only 8 per cent in the medical cohort, as compared with 5 per cent in the surgical cohort (not significant). The likelihood of nonfatal Q-wave myocardial infarction was 11 and 14 per cent, respectively (not significant). The five-year probability of remaining alive and free of infarction was 82 per cent in the patients assigned to medical therapy and 83 per cent in the patients assigned to surgery (not significant). There were no statistically significant differences in the survival rate or in the myocardial-infarction rate between subgroups of patients randomly assigned to medical and to surgical therapy when they were analyzed according to initial group assignment, number of diseased vessels, or ejection fraction. Therefore, as compared with medical therapy, coronary bypass surgery appears neither to prolong life nor to prevent myocardial infarction in patients who have mild angina or who are asymptomatic after infarction in the five-year period after coronary angiography.

Changes in cardiac functional capacity after coronary bypass surgery in relation to adequacy of revascularization

Seventy patients having aortocoronary vein bypass grafting surgery for angina pectoris underwent preoperative invasive exercise testing to symptom limits and again 6 to 14 months postoperatively. Cardiac output was measured using the direct Fick principle. Postoperatively at maximal exercise, there was a 3.11 liters/min (p less than 0.0001) increase in cardiac output in men (n = 61) and a 2.04 liters/min (p less than 0.01) increase in women (n = 9). Patients with complete revascularization showed a significantly greater improvement in cardiac output postoperatively than did those with incomplete revascularization (26 versus 6%, p less than 0.0001). The major reason for the increased maximal cardiac output was a marked increase in heart rate while stroke volume was maintained at the same preoperative level. These findings were true irrespective of preoperative use of beta-adrenergic blocking drugs.

The effect of crossovers on estimates of survival in medically treated patients with coronary artery disease

Among 1661 consecutive patients with significant coronary artery disease treated medically at the Duke University Medical Center, 239 have undergone aortocoronary bypass surgery after at least 6 months of medical management. The purpose of this investigation was twofold: (1) to identify the distinguishing characteristics of these treatment crossovers; and (2) to illustrate a method of estimating the effect that withdrawing the crossovers from the analysis would have on the survival of the medically managed patients. Of 81 baseline characteristics compared, 25 were significantly (p less than 0.05) different between crossovers and noncrossovers. These included five characteristics that had previously been determined to be independent predictors favoring improved survival in medically treated coronary artery disease. A Cox regression analysis identified six variables independently associated with the time until crossover surgery. Crossover patients were younger and had superior ventricular function. A hazard score, which summarized in a single variable the overall risk of mortality, was developed from the prognostic baseline characteristics. Crossover patients had significantly (p = 0.003) lower hazard scores and hence would have been expected to have a superior survival compared with noncrossover patients. In our series, survival in the medically treated patients would likely have been higher had the crossovers remained in the medical group.

Long-term exercise performance after percutaneous transluminal coronary angioplasty and coronary artery bypass grafting

In our first 169 consecutive patients admitted to undergo percutaneous transluminal coronary angioplasty (PTCA) serial bicycle ergometric exercise sessions were scheduled to assess long-term-exercise performance. In 160 of these 169 patients (95%) an average of seven ergometric measurements were available during a mean follow-up period of 29 months (range 1 to 60 months). Two groups were formed. One consisted of 132 patients in whom PTCA was successful and the other consisted of 28 patients with failure of PTCA who subsequently underwent coronary artery bypass grafting (CABG) either on an emergency basis (12 patients) or as an elective procedure (16 patients). Exercise performance was expressed as work capacity in watts according to the highest completed exercise stage. In the successful PTCA group the actual work capacities increased from 74 +/- 42 W (mean +/- SD) before PTCA to 122 +/- 47 W at the most recent follow-up examination. In patients who underwent emergency or elective CABG the respective figures were 73 +/- 34 or 65 +/- 37 W before surgery and 120 +/- 41 or 119 +/- 41 W at the most recent follow-up examination (p less than .005 for all preprocedure to postprocedure comparisons). Successful PTCA and CABG after failed PTCA improve work capacity significantly. Comparison of our results with those of surgical studies indicates that a failed attempt at PTCA before CABG does not compromise the functional outcome of the operation, regardless whether it is done on an emergency or on an elective basis.

Late exercise test results from a prospective randomized study of bypass surgery for stable angina

A prospective randomized study comparing coronary bypass surgery (group 1, 51 patients) to drug therapy (group 2, 49 patients) was initiated in 1981. Supine graded exercise testing (SGXT) was performed initially, at 6 months, and annually with a bicycle ergometer. The presence or absence of ischemic ST segment changes (positive or negative SGXT) and chest pain were recorded. Initially, 63% of all patients had positive SGXT. For group 2, the frequency of positive SGXT results did not change significantly at 6 months (58%) or at 5 years (52%). At 6 months the number of patients without chest pain increased in group 1 compared with group 2 (28/41 vs 13/41, respectively; p less than .002), but there was no difference in the frequency of positive SGXT results (20/41 vs 24/41, respectively; p = NS). This occurred because a majority of the group 1 patients with positive SGXT no longer had associated chest pain (group 1, 11/20, group 2, 3/24; p less than .007). This response was associated with incomplete revascularization in eight of these 11 group 1 patients and may result from "silent ischemia." At 5 years, no significant difference existed in the incidence of positive SGXT (group 1, 10/32 vs group 2, 12/23; p = NS), but group 1 patients continued to have a reduction (although not statistically significant) in the number of patients without chest pain (group 1, 19/32 vs group 2, 7/23). The incidences of death and myocardial infarction were not significantly different between groups. Fewer episodes of unstable angia occurred in group 1 (10/51 vs 19/49; p less than .05). The prognosis of group 1 patients with positive SGXT and no chest pain and incomplete revascularization was not different from that of the entire group.

Ten-year survival after coronary bypass surgery for unstable angina

We have assessed the long-term results of coronary bypass surgery performed for unstable angina in 1282 patients from 1970 to 1982. The operative mortality was 1.8 per cent; in the first 4 years it was 2.5 per cent, and in the last 8 1/2 years it was 1.7 per cent. Using actuarial techniques, we determined that the 5-year and 10-year survival rates (mean +/- S.E.) were 92 +/- 1 per cent and 83 +/- 2 per cent, respectively, for the whole group. For patients with "normal" left ventricular function, they were 92 +/- 2 per cent and 86 +/- 3 per cent, and for patients with "abnormal" left ventricular function 91 +/- 2 per cent and 79 +/- 4 per cent (P = 0.14). No significant differences were observed in the long-term survival for any of the three clinical subgroups of patients with unstable angina--angina at rest, angina after recovery from acute myocardial infarction, and progressive angina of recent onset (P = 0.49). The reoperation rates at 5 and 10 years were 6 +/- per cent and 17 +/- 3 per cent. Currently, 61 per cent of the survivors have no angina; angina occurs on severe exertion in 20 per cent, on ordinary exertion in 14 per cent, and on mild exertion in 5 per cent. We conclude that coronary bypass surgery is an effective form of therapy (for up to 10 years) in patients with unstable angina.

Persistent improvement after coronary bypass surgery: ergometric and angiographic correlations at 5 years

One hundred patients with angina pectoris who fulfilled specific entry criteria were randomly assigned to either medical therapy or bypass surgery. These groups were subjected to annual exercise testing during a 5-year follow-up period. The degree of revascularization was assessed by graft and native vessel angiography at 3 weeks, 1 year and 5 years after the operation. The exercise tolerance of the medical group remained largely unchanged during the follow-up. Eighty-five to 95% of the patients were using beta-blocking compounds at the successive testing situations. The surgical group exhibited a sustained improvement in exercise tolerance: Total work increased by 39-66% (p less than 0.02-0.001) and maximal ergometric load by 23-35% (p less than 0.01-0.001), and maximal ST depression decreased by 39-61% (p less than 0.05-0.001). The use of beta-blocking compounds in the surgical group steadily increased, from 44% at 6 months after operation to 63% of patients at 5 years. Division of the surgical group into subsets of complete and incomplete revascularization revealed that the improvement was confined to complete revascularization. Thus, the improved exercise tolerance after bypass surgery was a result of successful reestablishment of effective coronary perfusion; despite graft attrition (15% in 5 years) and new lesions in the native arteries, this improvement persisted for 5 years with appropriate medical therapy.

Effect of coronary artery bypass grafting on subsequent hospitalization

The rates of hospitalization during follow-up for a matched pair cohort of medically and surgically treated patients from the Angiography Registry of Seattle Heart Watch were compared. Medically and surgically treated patients were matched according to extent of disease, left ventricular ejection fraction, age, and 3 other survival rate-related characteristics. There was a 26% reduction in cardiovascular hospitalizations in the surgically treated patients (19%/year) compared with the medically treated patients (26%/year). This was due to a significant reduction in hospitalization rate for myocardial infarction (surgically treated patients 1.1%/year, medically treated patients 2.6%/year), and for other cardiovascular reasons (surgically treated patients 12.5%/year, medically treated patients 15.7%/year). No significant (p = 0.146) reduction occurred in hospitalization rate for chest pain not due to myocardial infarction (surgically treated patients 5.6%/year, medically treated patients 7.7%/year). When the perioperative infarctions are included for the surgical cohort, the overall myocardial infarction rate is not significantly different (p = 0.173) between the 2 treatment groups (surgically treated patients 1.9%/year, medically treated patients 2.6%/year). Acute myocardial infarction was an uncommon reason for hospitalization, accounting for only 8% (55 of 685) of all cardiovascular hospitalizations, and was not related to the number of stenotic vessels in medically treated patients.

Postoperative treadmill performance and graft patency after myocardial revascularization

In a prospective study, a random selection of 122 patients who had coronary artery bypass grafting were studied angiographically and given treadmill tests preoperatively and one year after operation, regardless of their symptoms. A total of 397 grafts were performed (average, 3.3 grafts per patient) on all primary and secondary coronary vessels deemed graftable. Complete coronary revascularization (grafts to vessels 1.5 mm or more in diameter with 50% or greater stenosis) was achieved in 104 patients (85%); 18 patients (15%) were considered incompletely revascularized. One hundred sixteen of the 397 grafts (29%) were to the left anterior descending (LAD) coronary artery, 99 (25%) to the right coronary artery, 126 (32%) to the obtuse marginal branch, 52 (13%) to the diagonal branch of the LAD coronary artery, and 4 (1%) to the septal coronary arteries. Overall results showed that patients with positive postoperative treadmill tests had a graft patency of 64%, compared with 86% for patients with negative treadmill tests (p less than 0.001). Completely revascularized patients with all grafts patent had a 4.8% (3/62) incidence of positive treadmill performance, compared with 60% (6/10) for incompletely revascularized patients with all grafts patent (p less than 0.001). Completely revascularized patients with positive treadmill tests had a graft patency of 58% (45/78), while those with negative treadmill evaluations had a graft patency of 86% (227/264) (p less than 0.001). The patency rate for incompletely revascularized patients with positive treadmill performance was 78% (25/32) and 87% (20/23) for those with negative treadmill performance. This difference was not statistically significant. This study shows that postoperative treadmill performance is highly dependent on completeness of revascularization and graft patency. It therefore supports the prognostic importance of regular treadmill exercise testing to monitor continued graft patency.

The randomized controlled clinical trial. Scientific and ethical bases

Randomized controlled trials are increasingly accepted in principle but not always in practice, particularly for surgical therapies. Successful surgical randomized controlled trials demonstrate their feasibility, and reports of uncontrolled surgical trials now commonly bear a statement that a definitive answer requires a controlled trial. Scientifically, the randomized controlled trial is the most powerful way to determine a result ascribable only to the trial treatment. Although randomized controlled trials can be imperfect or improperly conducted, they are designed to circumvent biased behavior by investigators. With candor in informed consent, the equal chance not to get a trial treatment makes the randomized controlled trial the most ethical design. Thus, scientific, behavioral, and ethical cases support the randomized controlled trial as the optimal method for investigation of nearly all therapeutic innovations and as a requirement for publication.

The role of the randomized clinical trial in the evaluation of new operations

Randomized trials that compare new operations with old ones or new regimens of invasive therapy with standard operations can make a substantial contribution to medical knowledge if the stipulations outlined in this article are followed. However, randomized trials that compare medical with surgical therapy have a number of additional problems and as a result rarely have a major impact on the practice of medicine.

Randomized versus historical controls for clinical trials

To compare the use of randomized controls (RCTs) and historical controls (HCTs) for clinical trials, we searched the literature for therapies studied by both methods. We found six therapies for which 50 RCTs and 56 HCTs were reported. Forty-four of 56 HCTs (79 percent) found the therapy better than the control regimen, but only 10 of 50 RCTs (20 percent) agreed. For each therapy, the treated patients in RCTs and HCTs of the same therapy was largely due to differences in outcome for the control groups, with HCT control patients generally doing worse than the RCT control groups. Adjustment of the outcomes of the HCTs for prognostic factors, when possible, did not appreciably change the results. The data suggest that biases in patient selection may irretrievably weight the outcome of HCts in favor of new therapies. RCTs may miss clinically important benefits because of inadequate attention to sample size. The predictive value of each might be improved by reconsidering the use of p less than 0.05 as the significance level for all types of clinical trials, and by the use of confidence intervals around estimates of treatment effects.

Long-term survival after coronary bypass surgery. Comparison of various subsets of patients with general population

Life-table analysis consecutive cases of isolated coronary bypass surgery at the Buffalo Hospital between 1973 and 1977 showed an estimated survival of 94 per cent at five years, equal to that of an age- and sex-matched group of the US population. Subsets of these patients divided according to sex, age, number of vessels narrowed, number of segments grafted, history of myocardial infarction, ejection fraction, and presence of unstable angina have estimated survivals not statistically less in any of these subsets than that of matched cohorts of the general population.