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Identifying Likelihood of Obstructive Coronary Disease in Patients With a Calcium Score of Zero: Separating the Wheat From the Chaff.

The presence of coronary artery calcium (CAC)—a pathognomonic marker of atherosclerosis—has emerged as a factor strongly associated with the development of adverse cardiovascular events. It is established that a zero CAC score is a unique negative risk marker, aptly referred to as the power of zero given its association with an exceedingly low event rate.1 This result permits a reclassification of risk incremental to conventional risk markers alone. However, as noncalcified plaque can occur, the presence of a zero CAC score is not identical to the absence of atherosclerosis. Noncalcific plaque formation can be dynamic, with a preponderance to develop and bring about symptoms in younger patients.2 The optimal evaluative approach to the symptomatic individual with a CAC score of zero is undefined. In the current issue, Alshahrani et al3 report a new clinical score predicting the presence of coronary computed tomography angiography (CCTA)–defined obstructive coronary artery disease (CAD) in patients with zero CAC. The score was based on a derivation cohort from a computed tomography registry4 of predominantly symptomatic patients (82%) with a CAC score of zero (n=4903) and validated in an independent cohort of 4290 mostly symptomatic patients (73%) from the Coronary CT Angiography Evaluation for Clinical Outcomes: an International Multicenter Registry multinational registry.5 Logistic regression modeling was applied to patient characteristics—patient sex, age, typical chest pain, dyslipidemia, hypertension, family history of CAD, and diabetes mellitus—to identify CCTA-defined obstructive CAD (stenosis ≥50%; 3.5% of patients). Based on weights of the β-coefficients, a score of ≤6 was considered low risk (negative predictive value, 99%; negative likelihood ratio, 0.42), scores of 7 to 13 were intermediate risk, and scores >14 were high risk for obstructive CAD (specificity, 98%; positive likelihood ratio, >5). The prognostic characteristics were examined in an underpowered small subanalysis with all-cause mortality over a median 2-year follow-up was 0.51% and 0.58% in the lowand intermediate-risk groups, respectively, versus 2% in the high-risk group. The results of the current study potentially aid the decisionmaking process in symptomatic patients with zero CAC. Study findings suggest that in low-risk individuals (risk score, ≤6), CCTA-defined obstructive CAD can be excluded with a high degree of certainty, potentially avoiding further investigation. © 2019 American Heart Association, Inc. Circulation: Cardiovascular Imaging