William O. Myers

Clinical and angiographic predictors of operative mortality from the collaborative study in coronary artery surgery (CASS).

Fifteen institutions participating in the Collaborative Study in Coronary Artery Surgery (CASS) have performed isolated coronary artery bypass surgery upon 6630 patients (1061 women and 5569 men) for coronary artery disease. The overall operative mortality (OM) was 2.3% (range 0.3–6.4%). Mortality increased with age, from 0 in the group 20–29 years old to 7.9% In the group 70 years and older. OM was higher for women in each age group, ranging from 2.8% for ages 30–39 years to 12.3% for age 70 years and older (0.8% and 5.8% for men). Clinical manifestations of congestive heart failure were associated with increased OM. Mortality was 1.4% in one-vessel, 2.1% in two-vessel and 2.8% in three-vessel disease (diameter narrowing ⩾ 70%). Among 1019 patients with left main coronary artery (LMCA) stenosis, OM ranged from 1.6% in patients with mild stenosis and a right-dominant system to 25% in patients with severe (⩾ 90%) stenosis and left dominance. OM varied with ejection fraction (EF) (1.9% for EF ⩾ 50% to 6.7% for EF < 19%) and left ventricular wall motion score (1.7% for least abnormal to 9.1% for most abnormal). For elective surgery, OM was 1.7%, for urgent surgery 3.5%, and for emergency surgery 10.8%. Mortality was 40.0% among 30 patients with severe LMCA stenosis who underwent emergency revascularization. Advanced age, female sex, symptoms of heart failure, LMCA stenosis, impaired left ventricular function and nonelective surgery are associated with a higher OM. These factors should be considered in the selection of patients for coronary artery surgery.

CASS registry: Long term surgical survival

Abstract Objectives To show the effect of clinical, angio and demographic traits on late survival of Coronary Artery Surgery Study (CASS) patients following coronary artery bypass grafting (CABG) and introduce Hazard Function analysis to CASS survival data. Methods Patients were reached by mail survey with 94% response. By National Death Index, vital status was obtained in 99.7% (n = 8221) with a mean follow up of 15 years. Cox proportional hazard and Blackstone Hazard Function regressions were used to assess effects of preoperative traits. Results Ninety percent of patients were alive at 5, 74% at 10 and 56% at 15 years. Of those age 65 and age 75 at operation, 74% and 59% were living at 10 years and 54% and 33% at 15 years (now age 90), survival exceeding the matched U.S. population. Hazard Function falls rapidly after CABG to 9 to 12 months, then rises, doubling by 15 years. Young patients, below age 35, had lower late survival. The time-segmented Cox model (divided at time suggested by the Hazard Function) identified traits showing predictive power early, throughout and late. Female sex, small body surface, ischemic symptoms and emergency status affected survival early. Heavier weight, infarct(s), diuretics, diabetes, smoking, left main and LAD stenosis and use of vein grafts only increased hazard late only. Conclusions There are still lessons from the CASS database. CABG in the elderly is supported by the survival pattern of our patients age 75 at operation. Time-segmented Cox analysis and Hazard Function analysis separate baseline variables into those that predict early mortality and those that predict long survival.

Comparison of operative mortality and morbidity for initial and repeat coronary artery bypass grafting: the coronary artery surgery study (CASS) registry experience

The National Heart, Lung, and Blood Institutes Coronary Artery Surgery Study (CASS) registry population was reviewed to allow comparison of operative mortality and morbidity rates for initial and repeat coronary artery bypass grafting (CABG) procedures. Standardized data collection was employed in CASS during patient entry (July 1, 1974, to May 31, 1979) and follow-up (ended November 30, 1982). Initial CABG was performed on 9,369 patients. Mean follow-up was 60.5 months. Repeat CABG was required in 283 patients (3.0%). The mean interval between operations was 39.3 months. Individuals needing reoperation tended to be young (p less than 0.0001) and female (p less than 0.002) and to have less extensive coronary artery disease (p less than or equal to 0.0001), less left ventricular impairment (p less than 0.0001), less evidence of congestive heart failure (p = 0.006), and fewer coronary vessel systems bypassed at the first operation (p less than 0.0001). Repeat CABG carried an increased risk of death compared with initial CABG (5.3% versus 3.1%, respectively; p less than 0.05). However, the rates of perioperative myocardial infarction (6.4% for repeat and 5.8% for initial CABG) and of all surgical complications combined (30.6% versus 27.9%) were not significantly different from those at initial CABG.

Prognostic significance of angiographically documented left ventricular aneurysm from the Coronary Artery Surgery Study (CASS)

In order to evaluate the prognosis of medically treated patients with angiographically defined left ventricular aneurysm the data available from 1,136 patients with aneurysm (7.6 percent) from 15,019 patients with coronary artery disease in the Coronary Artery Surgery Study (CASS) registry were analyzed. Prior myocardial infarction, reduced ejection fraction, absence of angina and evidence of congestive heart failure were more commonly present in patients with aneurysm. The cumulative survival rates of medically treated patients at 1, 2, 3 and 4 years were 90, 84, 79 and 71 percent, respectively. The Cox analysis of survival indicated that the following variables predicted outcome: age, residual left ventricular function as assessed with angiography, left ventricular end-diastolic pressure, functional impairment due to congestive heart failure, number of vessels diseased, mitral regurgitation and S3 gallop. When survival was stratified for similar degrees of left ventricular dysfunction and functional impairment there was no difference between the survival of patients with aneurysm and that of registry patients without aneurysm. The data from this large population study indicate that the survival of patients with left ventricular aneurysm is better than previously recognized. The mortality in this group is primarily related to age, left ventricular function and clinical severity of heart failure. The presence of an aneurysm does not independently alter survival.

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.

The influence of surgery on the natural history of angiographically documented left ventricular aneurysm: the Coronary Artery Surgery Study.

Coronary artery bypass surgery with or without aneurysmectomy has been used to treat patients with angiographically defined left ventricular aneurysm. To evaluate whether surgery benefits such patients, we analyzed the data from 1131 patients who were enrolled in the registry of the Coronary Artery Surgery Study. Four hundred sixty-seven patients underwent bypass surgery, of which 238 also had left ventricular resection, and 30 had resection alone. The overall operative mortality was 7.9%; the operative mortality was 7% for bypass alone compared with 9% for bypass surgery plus left ventricular resection (NS). Long-term survival by life-table analysis was similar for both medically and surgically treated patients (69% vs 67%, respectively). Cox survival analysis identified congestive heart failure score, duration of chest pain, extent of coronary disease, left ventricular end-diastolic pressure, age, and surgical therapy as important predictors of outcome. Patient subsets that showed improved survival with surgical therapy after adjustment for inequities in baseline characteristics were patients with three-vessel disease and those patients in moderate- and high-risk subgroups. Surgical therapy significantly reduced symptoms of angina and use of cardiac medications but the incidence of recurrent infarction was similar for both therapies.

Platelet Dysfunction Associated with Cardiopulmonary Bypass

The clinical significance and pathogenesis of the platelet dysfunction following cardiopulmonary bypass were studied in conjunction with the degree of functional impairment associated with the use of membrane and bubble oxygenators. Forty consecutive patients had the following tests preoperatively and postoperatively: complete blood count (CBC), platelet count, prothrombin consumption time, bleeding time, prothrombin time, partial thromboplastin time, fibrinogen, euglobulin clot lysis, fibrin degradation products, and platelet aggregation tests. Six patients were given 14C-serotonin tests before and after operation, and preoperative and postoperative electron micrographs were made of the platelets of 3 patients. The amount of blood lost, the blood transfused, and plasma hemoglobin levels were also measured. Abnormal aggregation of platelets was found, with no difference between the membrane and bubble oxygenators. In vitro aggregation tests with protamine sulfate and hemoglobin solutions, as well as the 14C-serotonin studies and electron micrographs, suggest that platelets acquire storage pool deficiency and an abnormal membrane during cardiopulmonary bypass.

Stroke in coronary artery bypass graft surgery: an analysis of the CASS experience

An analysis of the Coronary Artery Surgery Registry (CASS) was performed to determine the occurrence of stroke after coronary artery bypass surgery in patients entered into the Coronary Artery Surgery Study Registry. Of the 10,098 patients having coronary artery bypass surgery at the Coronary Artery Surgery Study participating sites during the period July 1974 through May 1979, a total of 348 patients (or 3.4%) sustained a stroke during the first year after coronary bypass surgery. Fifty-nine strokes occurred on the day of surgery, and an additional 129 strokes occurred during hospitalization for coronary bypass surgery. Thus, 188 patients (1.9%) of the entire surgical group sustained a stroke during initial hospitalization for coronary artery bypass surgery. Logistic regression analysis was used to predict stroke on the day of surgery, during the hospitalization for surgery, and during the first year after surgery. The most powerful predictors of stroke on the day of coronary artery bypass surgery were: 1) older age (n = less than 0.0001); 2) use of alpha-adrenergic drugs after bypass (n = 0.0001); and 3) longer duration of cardiopulmonary bypass (n = 0.002). For those strokes occurring at least 1 day after coronary artery bypass but during the initial hospitalization, age and duration of cardiopulmonary bypass were the most powerful predictors of stroke. An analysis of predictors of stroke within 1 yr after hospital dismissal for initial coronary bypass surgery revealed that the most powerful predictor was a history of previous cerebrovascular disease (n less than 0.0001) and a history of hypertension (n less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Medical versus Early Surgical Therapy in Patients with Triple-Vessel Disease and Mild Angina Pectoris: A CASS Registry Study of Survival

Results of coronary artery bypass grafting were evaluated in 856 nonrandomized patients in the Coronary Artery Surgery Study (CASS) registry with mild angina (Canadian Cardiovascular Society Classes I and II) and three-vessel disease, defined as 70% or more stenosis in the proximal or middle segment of the three major coronary arteries. There were 413 patients with medical therapy and 443 with early operation. Patients with delayed operation were kept in the medical group for analysis. Six-year survival adjusted for left ventricular (LV) function and number of proximal stenoses was 67% for medical and 84% for surgical patients (p less than 0.0001). Patients with normal LV function had equal survival with medicine or surgical intervention. Those with mild or moderate LV dysfunction (CASS LV wall motion score 6 to 9 and 10 to 15, respectively) and at least one proximal stenosis (the dominant right coronary artery) had increased probability of being alive at six years with surgical treatment. In patients with severe LV impairment (LV score higher than 15) and in those whose only proximal stenosis of 70% or more (in three-vessel disease) was located in the left anterior descending coronary artery, increased survival with surgical treatment could not be demonstrated. This is a nonrandomized observational study with the limitations of such studies: the need to adjust for differences in baseline traits between medical and surgical groups and the possibility of an unrecognized imbalance in baseline characteristics. In a Cox analysis of variables influencing outcome, early surgical treatment was an independent predictor of survival with 43% the risk of medical treatment (95% confidence range: 29 to 62%). Adjustment by propensity analysis to reduce selection bias from known differences in baseline variables did not alter results.

Comparison of effects of medical and surgical therapy on survival in severe angina pectoris and two-vessel coronary artery disease with and without left ventricular dysfunction: A coronary artery surgery study registry study

This nonrandomized study compared the results of early coronary artery bypass grafting to those of initial medical therapy in a group of 2,023 patients with severe angina pectoris and 2 major epicardial coronary arteries having greater than or equal to 70% diameter luminal narrowing. Medical therapy was selected for 706 patients, and 1,317 patients were treated by coronary artery bypass grafting. The 6-year survival rate was 76% for patients treated medically and 89% for patients treated surgically (p less than 0.0001). Cox multivariate analysis showed that surgical treatment was a beneficial independent predictor of survival (p less than 0.001). For patients with 2-vessel coronary artery disease who had Canadian Heart Association class III and IV angina at presentation, surgical therapy provided a survival advantage for patients with impaired left ventricular function and proximal narrowing of 1 or more coronary arteries.