EXERCISE MYOCARDIAL PERFUSION SPECT IN PATIENTS WITHOUT KNOWN CORONARY-ARTERY DISEASE - INCREMENTAL PROGNOSTIC VALUE AND USE IN RISK STRATIFICATION

Background We evaluated the incremental prognostic value, the role in risk stratification, and the impact on patient management of myocardia l perfusion single-photon emission computed tomography (SPECT) in a po pulation of patients without prior myocardial infarction, catheterizat ion, or revascularization. Methods and Results We examined 2200 consec utive patients who at the time of their dual-isotope SPECT had not und ergone catheterization, coronary artery bypass surgery, or percutaneou s transluminal coronary angioplasty and had no known history of previo us myocardial infarction. Follow-up was performed at a mean of 566+/-1 42 days (97% complete) for hard events (cardiac death and myocardial i nfarction) and for referral to cardiac catheterization or revasculariz ation within 60 days after nuclear testing. Examination of clinical, e xercise, and nuclear models by use of pre-exercise tolerance test (ETT ), post-ETT, and nuclear information using a stepwise Cox proportional hazards model and receiver-operating characteristic curve analysis re vealed that nuclear testing added incremental prognostic value after i nclusion of the most predictive clinical and exercise variables (globa l chi(2)=12 for clinical variables; 31 for clinical + exercise variabl es; 169 for nuclear variables; gain in chi(2), P<.0001 for all; receiv er-operating characteristic areas: 0.66+/-0.04 for clinical, 0.73+/-0. 04 for clinical + exercise variables, 0.87+/-0.03 for nuclear variable s, P=.03 for gain in area with exercise variables; P<.001 for increase with nuclear variables). Multiple logistic regression analysis reveal ed that scan information contributed 95% of the information regarding referral to catheterization with further additional information provid ed by presenting symptoms and exercise-induced ischemia. Referral rate s to early catheterization and revascularization paralleled the hard e vent rates in all scan categories-very low referral rates in patients with normal scans and significant increases in referral rates as a fun ction of worsening scan results. Even after stratification by clinical and exercise variables such as the Duke treadmill score, pre- and pos t-ETT likelihood of coronary artery disease, presenting symptoms, sex, and age, the nuclear scan results further risk-stratified the patient subgroups, thus demonstrating clinical incremental value. Conclusions In a patient population with no evidence of previous coronary artery disease at overall low risk (1.8% hard event rate), myocardial perfusi on SPECT adds incremental prognostic information and risk-stratifies p atients even after clinical and exercise information is known. It appe ars that referring physicians use this test in an appropriate manner i n selecting patients to be referred to catheterization or revasculariz ation.