Coronary Artery Surgery Study (CASS)
Condition: Cardiovascular Diseases; Coronary Disease; Heart Diseases; Myocardial Ischemia
MeSH terms: Cardiovascular Diseases; Heart Diseases; Coronary Disease; Myocardial Ischemia; Ischemia
Study type: Interventional
Phase: Phase 3

Summary: 
      To compare coronary artery surgery with medical management in patients with coronary artery
      disease and to maintain a registry on all patients undergoing coronary arteriography, whether
      operatively or medically managed.
    

Detailed description: 
      BACKGROUND:

      Although it was generally agreed that many patients with severe angina pectoris improved
      symptomatically after coronary artery surgery, there was less consensus concerning, for
      example, other effects of the procedure, such as its long-term benefit and the criteria for
      patient selection. In addition, there were fewer data and less agreement on the effects and
      proper role of this procedure in other clinical circumstances. Both the surgical procedure
      and the prior diagnostic procedures represented substantial costs in both monetary and
      manpower terms; moreover, they entailed morbidity and mortality risks.

      There existed an urgent need for reliable and quantitative information regarding the effects
      of coronary artery surgery in patients with ischemic heart disease. To be meaningful, these
      data had to be set into the perspective of the clinical course of such patients under medical
      treatment.

      This assessment presupposed a meaningful classification of these patients and of the
      therapeutic interventions as well as evaluations of the effects of surgical and medical
      regimens in terms of mortality, the quality of life, and objective hemodynamic and other
      physiological measurements. Only such information could provide sufficient background for
      determining the suitability of coronary artery surgery for a particular patient.

      In 1972, the National Heart and Lung Advisory Council identified these questions as topics of
      high priority, and the National Heart and Lung Institute established an Ad Hoc Policy
      Advisory Board on Coronary Artery Surgery to assist it in developing a program of research
      activities. In its report, the Board noted a 'critical need for objective data on the long-
      and short-term effects of coronary artery surgery.' Requests for proposals were issued to
      carry out the recommendations of the Board.

      Planning of the trial was conducted between June 1973 and April 1975 and included protocol
      design, the development of a manual of operations, and a pilot study of the registry. In
      August 1975, registry patients' entry and randomization began at the 11 clinical centers and
      coordinating center. Initial projections of patient population numbers were underestimated;
      therefore, five clinical centers were added to the trial in 1976.

      The five clinical subgroups of patients in the randomized studies included: stable angina
      with normal resting left ventricular function; stable angina with impaired left ventricular
      function; post-myocardial infarction without angina; congestive heart failure due primarily
      to ischemic heart disease; and patients previously asymptomatic who were discovered to have
      serious coronary artery disease. All of the above subgroups must have met specifically
      outlined clinical and angiographic criteria to be placed in the randomized subset. The other
      two subsets (as distinguished from subgroups) of the study included those patients who were
      unsuitable for randomization because surgery was the treatment of choice in the judgment of
      many physicians and those patients for whom medical management was the treatment of choice.
      The patients enrolled in both the registry and randomized trial were followed for a 10-year
      period. This allowed evaluation of the primary endpoints, death and myocardial infarction,
      and the secondary endpoints, angina, status, and quality of life.

      A total of 24,959 patients were entered into the registry; 780 patients were entered into the
      trial. Recruitment ended in 1979. Intervention ended in June 1983. Follow-up was extended for
      an additional five years to June 1989. Data analysis continued through May 1995 with grant
      support.

      DESIGN NARRATIVE:

      Randomized, non-blind, sequential. Some 780 patients meeting the criteria of specific subsets
      based on history, physical exam, laboratory tests, catheterization, and angiography were
      randomized to either surgical or medical therapy. Primary endpoints included death and
      myocardial infarction.
    

Intervention name(s): coronary artery bypass
Intervention type(s): Procedure
Allocation: Randomized
Primary purpose: Treatment