Does Prophylactic Coronary Artery Revascularization for High Risk Patients Reduce Long-term Risk of Mortality

CSP #411 - The Coronary Artery Revascularization Prophylaxis (CARP) Trial

Although a number of sophisticated diagnostic tests have been shown to be helpful in identifying patients at high risk for perioperative cardiac complications, no study has addressed the most important question: Should prophylactic coronary revascularization be performed prior to elective vascular surgery? This study is designed to answer this question.

Primary Hypothesis: Prophylactic coronary artery revascularization in high risk patients scheduled for elective vascular surgery reduces long-term risk of mortality.

Secondary Hypotheses: Prophylactic coronary artery revascularization in high risk patients scheduled for elective vascular surgery reduces long-term risk of myocardial infarction and improves both cost-effectiveness of treatment and quality of life of the patients.

Intervention: 1) Medical therapy. This is the current, conservative practice. Each local investigator will decide the best medical treatment consistent with that given to any patient scheduled for elective vascular surgery. In patients with coronary artery disease, long-term treatment would be expected to include a combination of antiplatelet agents, beta-blockers, calcium channel blockers, and nitrates. Vascular surgery should occur as soon as possible but no later than three months after randomization. 2) Coronary artery revascularization. Repair of the heart in patients with coronary artery disease may aid in the protection of these patients when they undergo vascular surgery. The surgeon is free to choose between coronary artery bypass grafting (CABG) and percutaneous transluminal coronary angioplasty (PTCA). Coronary artery revascularization should occur as soon as possible after randomization. Vascular surgery should occur between one and three months following CABG or between three to four days and three months following PTCA.

Primary Outcomes: Long-term mortality, MI, and quality of life.

Study Abstract: Cardiovascular disease accounts for one million deaths per year and is the major cause of mortality among Americans. Studies have shown that in patients scheduled for elective vascular surgery, the prevalence of coronary artery disease exceeds 50%. It is not surprising, therefore, that "perioperative cardiac morbidity" defined as the occurrence of MI, unstable angina, CHF, arrhythmias, and cardiac death, is the leading cause of perioperative complications. Although a number of sophisticated diagnostic tests have been shown to be helpful in identifying patients at high risk for perioperative cardiac complications, no study has addressed the most important question: Should prophylactic coronary revascularization be performed prior to elective vascular surgery? This study is designed to answer this question.

STUDY DESIGN This proposal utilizes a prospective, randomized trial to test whether prophylactic coronary revascularization reduces perioperative cardiac complications and long term mortality in patients who undergo elective vascular surgery. All VA patients requiring elective vascular surgery will be screened for enrollment. Patients will be excluded from enrollment if they need urgent/emergent vascular surgery; have had previous coronary artery revascularization with no current ischemia; or have one or more serious medical conditions such as COPD (FEV1<1.0), renal dysfunction (creatinine >3.5 mg/dl), liver failure, metastatic cancer, severe dementia, stroke, or unstable angina. Eligibility for the study is based on results from coronary angiography. Patients having clinical risk factors (including history of MI, pathologic Q-waves, ventricular ectopy requiring antiarrhythmic therapy, diabetes, angina, and CHF); and/or a positive stress test; should be candidates for coronary angiography. Specific angiographic criteria will exclude individuals from subsequent randomization. These include normal coronary arteries, severe LV dysfunction (EF<20%), aortic valve area <1 cm2, and left main disease (or equivalent). Patients considered nonintervenable by the cardiologist or cardiac surgeon will also be excluded. Enrolled patients who do not meet any of the exclusion criteria will then be randomized to either medical treatment or prophylactic revascularization. The decision to proceed with either PTCA or CABG will be based on institutional experiences. The study design does not compare PTCA versus CABG, but rather tests whether any revascularization procedure proves beneficial. The stratification factors will be the participating hospital and the type of vascular procedure that has been proposed (intraabdominal or infrainguinal). The randomization scheme is stratified by type of vascular surgery because aortic procedures (intraabdominal) may carry more risk than peripheral procedures (infrainguinal).

STATISTICAL CONSIDERATIONS For this trial, a sample size of 560 randomized patients will be required. This will provide 90% power to detect a difference in 3.5 year survival rates of 85% for patients receiving prophylactic coronary artery revascularization versus 75% for patients receiving medical treatment. Allowing for a 10% post randomization dropout rate, the target sample size will be 620 patients. Assuming an average intake of one patient per hospital per month, 18 participating hospitals will be required.

STUDY PHASES The study originally was funded for a one year pilot phase. The purpose of this phase was to determine the feasibility of randomizing one patient per hospital per month. In order for the study to enter the main phase, five pilot hospitals, ranging in number of vascular surgery cases from low to high, had to achieve at least 90% of patient accrual expectations (54 out of an expected 60 patients randomized in one year). After successful completion of the pilot phase, the main study was approved. During the main phase, 18 participating hospitals will accrue patients for four years and continue postvascular surgery follow-up for one year.

Inclusion Criteria:

High risk patients scheduled for elective vascular surgery

Exclusion Criteria: