Multidetector computed tomography coronary artery plaque predictors of stress-induced myocardial ischemia by SPECT.

BACKGROUND: Atherosclerosis imaging by multidetector computed tomography (MDCT) detects coronary artery plaque extent, distribution, location and composition. In contrast, functional imaging by single-photon emission computed tomography (SPECT) identifies perfusion defects known to predict prognosis of coronary heart disease (CHD). We sought to determine whether anatomic measures of plaque by MDCT predict functional measures of CHD by SPECT and thus, serve as measures of adverse cardiovascular prognosis. METHODS AND
RESULTS: Consecutive low-to-intermediate risk symptomatic patients without known CHD (n=163) underwent both stress SPECT and MDCT. MDCT plaque extent and distribution were graded by a segment stenosis score (summation of luminal obstruction in all coronary segments) and segment involvement score (summation of segments exhibiting any plaque), respectively. Plaque location was assessed with a segments-at-risk score (plaque extent weighted by proximity) and a modified Duke CAD index. Plaque composition was graded as non-calcified, calcified and mixed. SPECT findings--summed stress (SSS), rest (SRS) and difference (SDS) scores--were compared to MDCT plaque scores. In univariate analyses, segment stenosis score (p=0.006), segments-at-risk score (p=0.002), Duke CAD index (p=0.02), and mixed plaque score (p=0.01) predicted severely abnormal SPECT. Highest compared to lowest quartile mixed plaque scores were predictive of higher SSS (8.1+/-10.3 versus 3.5+/-5.7, p<0.001), SRS (3.2+/-7.7 versus 0.9+/-3.1, p=0.008), and SDS (4.9+/-6.4 versus 2.6+/-3.9, p=0.012). In contrast, higher segment involvement scores, calcified and non-calcified plaque scores did not predict higher SPECT measures of ischemia. In multivariable analyses, comparing highest to lowest quartiles, individuals with high segment stenosis scores [odds ratio (OR) 1.97 (1.22-3.39), p=0.008], segments-at-risk scores [OR 1.71 (1.24-2.58), p=0.005], highest risk Duke CAD index category [OR 2.25 (1.12-4.41), p=0.02], and mixed plaque scores [OR 1.64 (1.10-2.43), p=0.01] had more severely abnormal SPECT scans.
CONCLUSIONS: In low-to-intermediate risk patients without known CHD, MDCT coronary artery plaque assessment successfully identify patients at higher risk of increased extent, severity and reversibility of myocardial perfusion defects by SPECT. Anatomic MDCT findings, including plaque extent, location and composition, are independent predictors of functional ischemia and severe CHD by SPECT and thus, represent markers of adverse cardiovascular prognosis prior to the occurrence of clinical cardiovascular events.