Threshold, incidence, and predictors of prognostically high-risk silent ischemia in asymptomatic patients without prior diagnosis of coronary artery disease

BACKGROUND: Little is known about incidence, threshold, and predictors of prognostically relevant silent ischemia (SI). The aim was to study these three aspects of silent coronary artery disease (CAD). METHODS: In total, 3,664 consecutive asymptomatic patients without prior diagnosis of CAD undergoing myocardial perfusion SPECT (MPS) were evaluated and followed-up < or = 1 year for Events (HE): cardiac death or myocardial infarction. MPS was interpreted using a 20 segment model to define summed stress, rest, and difference scores (the extent of % myocardium ischemic was derived). Prognostic high-risk ischemia was defined as ischemia consistent with a HE rate < or = 3%. RESULTS: Overall, < or = 7.5% myocardium ischemic was consistent with high risk. Twenty-one and six percent of patients had ischemia and high-risk ischemia, respectively. Patients with high-risk ischemia had a worse prognosis than patients with less SI, HE rate of 3.1 and 0.4%, respectively, (P = .0001). Sex, age, diabetes, hypertension, abnormal resting ECG, angina, peak heart rate, blood pressure during treadmill testing, ST-depression, and Duke treadmill score were independent predictors of relevant SI. CONCLUSIONS: In total, < or = 7.5% myocardium ischemic revealed to be consistent with high risk. Six percent of patients had evidence of high-risk SI. Diagnostic scores are provided to most likely identify patients with high-risk SI.