The Journal of Thoracic and Cardiovascular Surgery, Vol 90, 541-548, Copyright © 1985 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
The Coronary Artery Surgery Study (CASS). A critical appraisal
GS Weinstein and B Levin
The applicability of the Coronary Artery Surgery Study (CASS) to clinical
practice is seriously hampered by the following findings. (1) The CASS
randomized study applies to only a small minority of patients with coronary
artery disease. Attempts to extend the conclusions of CASS to the vast
majority of patients with coronary artery disease are unjustified. (2) The
high percentage of crossover of the medical group made it impossible for
CASS to accomplish its primary goal of contrasting medical and surgical
treatment. (3) Despite the fact that crossover of medically assigned
patients created a bias against surgical treatment, the observed mortality
in the surgical group was still 31% lower than that in the medical group.
(4) The failure of CASS to find this difference to be statistically
significant must take into account the fact that the statistical power of
CASS was so low that a real difference was likely to be overlooked. (5) The
conclusion that patients similar to those in the study may safely defer
operation is unwarranted and violates the principles of prospective study
design. In addition, CASS failed to address the possibility that deferring
operation may compromise long-term survival.