Clinical Alert: Bypass Over Angioplasty for Patients with Diabetes
Between August 1988 and August 1991, 18 clinical centers randomized 1,829 patients, ages 17 to 80 and including 353 on drug treatment for diabetes. Half of the patients were randomly assigned to PTCA and the other half to CABG. At baseline, the mean age of the randomized patients was 61 years. Thirty-nine percent of the randomized patients were age 65 or older, 27 percent were women, 25 percent were classified as having diabetes (of these, 76 percent were being treated with oral hypoglycemic agents or insulin), 60 percent had two-vessel disease and 40 percent had three-vessel disease, and 98 percent had angina (of these, 64 percent had unstable angina and 17 percent had class 3-4 angina). At the time of this alert, 66 percent of patients had completed follow-up. Patients will be followed for a minimum of 7 years. The trial is expected to finish follow-up on all patients by November 1998.
Follow-up includes annual functional status assessments and an electrocardiogram (ECG), and a biennial exercise stress test. As required by the protocol, risk factor modification was initiated for all patients after their enrollment. This includes help with smoking cessation, exercise, and diet. Patients also were treated as needed for hypertension, elevated blood cholesterol, and diabetes. Risk factors and medical problems were managed by each patient's primary care physician.
The trial has been closely monitored by both the study chairman (Dr. Robert Frye, Mayo Clinic Foundation), the Clinical Coordinating Center (Dr. Katherine Detre, University of Pittsburgh), and the independent Data and Safety Monitoring Board (chaired by Dr. J. David Bristow, Oregon Health Sciences University). The Data and Safety Monitoring Board is composed of PTCA experts, cardiovascular surgeons, clinical cardiologists, and experts in biostatistics and ethics. The Board regularly reviews the monitoring reports. ECG analyses are being done by the Central ECG Laboratory (Dr. Bernard R. Chaitman, director) at the St. Louis University Medical Center. An independent Mortality and Morbidity Classification Committee (chaired by Dr. Ronald Prineas, University of Miami) categorizes fatal events in the trial.
On September 13, 1995, the Data and Safety Monitoring Board held an urgent session to review the 5-year mortality data. The Board concluded that the unfavorable mortality results for the patients on drug treatment for diabetes and first treated with PTCA were unlikely to be due to chance. The Board recommended to the National Institutes of Health that physicians and other health care professionals and the public be promptly informed of the results.