Incremental prognostic value of calcified vs non-calcified plaque burden on computed tomography angiography and myocardial perfusion imaging

Abstract

Abstract Funding Acknowledgements Type of funding sources: None. Background Coronary computed tomography angiography (CCTA) is currently guideline-endorsed for diagnosing suspected coronary artery disease (CAD) in low-intermediate risk patients. Single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) has an established role in both the accurate detection of ischemia and identification of patients at high risk of future cardiovascular events. Recent studies have shown that the burden of atherosclerotic plaque is an independent predictor of cardiovascular events, and that this effect depends on the degree of calcification. Purpose To compare the incremental prognostic value of calcified vs non-calcified plaque burden to CCTA anatomic assessment and SPECT physiologic assessment in patients evaluated with both tests. Methods Consecutive patients who underwent clinically indicated CCTA and SPECT myocardial imaging for suspected CAD were included. Ischemia on SPECT was defined as summed difference score > 0 using perfusion graded on a 5-point scale. Anatomically obstructive CAD by CCTA was defined as ≥50% in the left main artery and ≥70% stenosis severity in proximal, mid and distal branches of the left anterior descending, left circumflex and right coronary artery without including side branches. Segment involvement score was defined as the sum of segments with plaque irrespective of the degree of stenosis using an 18-segment coronary artery model. A Hounsfield unit threshold of > =130 was used to classify plaques composition as calcified/mixed (C-SIS) vs non-calcified plaque (NC-SIS). Patients were followed for major adverse cardiovascular events (MACE, inclusive of all-cause death, non-fatal myocardial infarction, and percutaneous coronary intervention or coronary artery bypass grafting 90-days after imaging test.) Results A total of 956 patients were included. (Mean age 61.1 ± 14.2 years, 54% men, 89% hypertension, 81% diabetes, 84% dyslipidemia). Obstructive stenosis (left main ≥ 50%, all other coronary segments ≥ 70%) and ischemia were observed in similar number of patients (14%). After a median follow-up of 31 months, 102 patients (11%, 29.2 events per 1000 person-year) experienced a MACE. In multivariable Cox regression models, C-SIS, but not NC-SIS significantly predicted outcomes and improved risk discrimination in models with CCTA obstructive stenosis (HR 1.14 95% CI 1.08 - 1.20 p= <0.001; Harrel’s C 0.74, p = 0.011) and SPECT ischemia (HR 1.14 95% CI 1.08 - 1.20, p < 0.001; Harrel’s C 0.76, p = 0.015). Conclusion In the current study of high-risk patients with suspected CAD, calcified plaque burden, but not non-calcified plaque incrementally added to measures in predicting incident cardiovascular outcomes