THE COMBINATION OF CAROTID ULTRASOUND PLAQUE QUANTIFICATION AND STRESS TESTING ENHANCES PATIENT SELECTION FOR CORONARY ANGIOGRAPHY

Abstract

BACKGROUND: Stress testing is commonly used to select patients for angiography. Recent studies have shown that up to 25% of angiograms may be unnecessarily conducted whereas some patients requiring angiography may not be referred, reflecting the limitations of stress testing and traditional risk factor scores. Our objective was to determine whether addition of carotid ultrasound to stress testing enhanced sensitivity for the prediction of coronary artery disease (CAD) and improved selection of patients requiring angiogram. METHODS: Carotid ultrasound was performed in 209 consecutive outpatients undergoing same-day angiography. All patients had received an imaging based stress test within 3 months. Mean far distal carotid intima-media thickness (CIMT) and maximal plaque height (thickness) were measured and compared to angiographic scores for prediction of CAD. Significant CAD was defined as presence of at least one major epicardial coronary vessel with 50% luminal narrowing. Literature threshold values for increased CIMT ( 0.8 mm) and plaque definition ( 1.5 mm) were used as cut-offs for stratifying patients as low or high risk for CAD. Stress test and ultrasound results, alone or combined, were analyzed for accuracy in stratifying risk. RESULTS: Plaque height by carotid ultrasound, in addition to stress testing, increased the overall test negative predictive value (NPV) from 28% to 71%, increased the sensitivity from 78% to 99%, and improved the negative likelihood ratio (LR-) from 1.27 to 0.20 for the detection of CAD. The combination of stress testing with carotid ultrasound would have appropriately re-stratified 34 out of 36 patients (who had received negative/equivocal stress test results) from low risk to high risk, as confirmed by coronary angiography. See Table 1. CONCLUSION: In symptomatic patients undergoing stress testing, both CIMT and carotid plaque quantification improves the identification of patients with significant coronary stenosis. Carotid plaque height quantification is superior to CIMT, and improves the NPV of stress testing by 43%. The combination of carotid ultrasound with stress testing is a potential clinical tool to rule out significant CAD and enhance selection of patients requiring angiography.