Serial Coronary Plaque Assessment Using Computed Tomography Coronary Angiography: A Comparison With Intravascular Ultrasound

Abstract

March 2019 1 Ravi Kiran Munnur, MBBS, PhD Jordan Andrews, BS Yu Kataoka, MBBS, PhD Peter J. Psaltis, MBBS (Hons), PhD Stephen J. Nicholls, MBBS, PhD Yuvaraj Malaiapan, MBBS, MD Sujith Seneviratne, MBBS (Hons) James D. Cameron, MBBS, MD Dennis T.L. Wong, MBBS (Hons), MD, PhD A direct relationship exists between the burden and progression of coronary atherosclerosis with adverse cardiovascular events.1 Intravascular ultrasound (IVUS) is the current reference standard test for coronary plaque assessment, limited by high cost and invasive nature of the test. Computed tomography coronary angiography (CTCA) has been proposed as a potential noninvasive tool to assess plaque changes and to test the efficacy of antiatherosclerotic medical therapies, and studies have shown good correlation between CTCA and IVUS for plaque quantification.2 However, it will be important to demonstrate comparability of CTCA and IVUS in serial plaque measurement. We studied nonculprit arteries in 10 patients (7 men; age, 61±5.4 years; 8 patients with stable coronary artery disease and 2 with acute coronary syndrome) in a prospective study who underwent serial (median interval of 334.5 [interquartile range, 288–438] days) invasive coronary angiography, IVUS, and CTCA performed within 2 weeks of interval at each time point. All the patients in the study were on optimal medical therapy, including statins. CTCA was performed on a 320-detector row scanner using previously described protocol.3 The institutional ethics committee approved the study, and all the subjects gave informed consent. The data that support the findings of this study are available from the corresponding author on reasonable request. All scan parameters at baseline and follow-up CTCA were kept identical. CTCA analysis was performed using a dedicated attenuation-based software tool (Sure Plaque, Vitrea 6, version 3.0; Vital Images and Toshiba Medical Systems) by an experienced cardiologist (R.K.M.) blinded to IVUS findings. Manual quantification of plaque burden was performed after delineation of the lumen and the outer vessel wall using the window settings of 230 W and 83 L (if the luminal HU was <500), and settings of 300 W and 150 L (if the luminal HU was >500) were used4 to improve edge detection. Additional window and level settings of 740 W and 220 L were used if necessary, to assess outer vessel wall5 (Figure). IVUS was performed in a standard fashion using the 40 MHz, Atlantis SR Pro (Boston Scientific) catheter, and all images were analyzed in a core laboratory, which was blinded to CTCA findings according to methods well-described previously.1 Plaque geometry and composition was quantified after spatial coregistration using fiduciary points on segmental and slice-by-slice (0.5 mm sections) basis on IVUS and CTCA. Baseline and follow-up plaque volume, percent atheroma volume (PAV), and total atheroma volume (TAV) were assessed. PAV and normalized TAV change were calculated and compared between CTCA and IVUS. A total of 300 cross-sectional images were analyzed (median, 31.5 per patient). Manual quantification of plaque on CTCA required an average analysis time of 45 minutes for each vessel. There was no significant difference in plaque volume, PAV, and TAV measurements between CTCA and IVUS at baseline and follow-up. PAV change (−2.61±3.44 versus 0±4.88; P=0.53, r=0.65) was moderately correlated with © 2019 American Heart Association, Inc. RESEARCH LETTER