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Coronary artery surgery study (CASS): a randomized trial of coronary artery bypass surgery. Survival data
Insights
Coronary Artery Surgery Study (CASS) found similar survival rates for bypass surgery and medical therapy in stable ischemic heart disease patients. Deferring bypass surgery is safe until symptoms necessitate intervention.
Area of Science:
- Cardiology
- Clinical Trials
- Health Services Research
Background:
- Stable ischemic heart disease management involves evaluating surgical versus medical treatment options.
- The Coronary Artery Surgery Study (CASS) aimed to compare outcomes of coronary artery bypass surgery and nonsurgical treatment.
Purpose of the Study:
- To assess the impact of coronary artery bypass surgery on mortality and nonfatal endpoints in patients with stable ischemic heart disease.
- To determine if early bypass surgery offers survival benefits over medical management.
Main Methods:
- A multicenter randomized controlled trial involving 780 patients with stable ischemic heart disease.
- Patients were randomly assigned to surgical (n=390) or nonsurgical (n=390) treatment and followed for mortality and nonfatal events.
- Data collection occurred from August 1975 to April 1983.
Main Results:
- At 5 years, the average annual mortality rate was 1.1% for surgical treatment and 1.6% for medical therapy.
- No statistically significant differences in annual mortality rates were observed between surgical and medical groups across different vessel disease severities.
- Survival rates were similar between groups, even in patients with good ejection fractions (≥0.50).
Conclusions:
- Patients with stable ischemic heart disease similar to those in the CASS trial can safely defer bypass surgery.
- Medical management is a viable option, with surgery reserved for cases where symptoms worsen and require palliation.
- The study highlights excellent survival rates for both treatment strategies in the studied population.
Abstract:
CASS includes a multicenter patient registry and a randomized controlled clinical trial. It is designed to assess the effect of coronary artery bypass surgery on mortality and selected nonfatal end points. From August 1975 to May 1979, 780 patients with stable ischemic heart disease were randomly assigned to receive surgical (n = 390) or nonsurgical (n = 390) treatment and were followed through April 15, 1983. At 5 years, the average annual mortality rate in patients assigned to surgical treatment was 1.1%. The annual mortality rate in those receiving medical therapy was 1.6%. Annual mortality rates in patients with single-, double-, and triple-vessel disease who were in the surgical group were 0.7%, 1.0%, and 1.5%; the corresponding rates in patients in the medical group were 1.4%, 1.2%, and 2.1%. The differences were not statistically significant. Nearly 75% of the patients had entry ejection fractions of at least 0.50. The annual mortality rates in patients in the surgical group in this subgroup with single-, double-, and triple-vessel disease were 0.8%, 0.8%, and 1.2% and corresponding rates in the medical group were 1.1%, 0.6%, and 1.2%. The annual rate of bypass surgery in patients who were initially assigned to receive medical treatment was 4.7%. The excellent survival rates observed both in CASS patients assigned to receive medical and those assigned to receive surgical therapy and the similarity of survival rates in the two groups of patients in this randomized trial lead to the conclusion that patients similar to those enrolled in this trial can safely defer bypass surgery until symptoms worsen to the point that surgical palliation is required.