Establishing the warranty of a coronary artery calcium score of zero

Mahmoud Al Rifai, Miguel Cainzos-Achirica, Michael J. Blaha
2015 Atherosclerosis  
The inherent limitations of traditional risk factor-based cardiovascular disease (CVD) risk assessment [1] have triggered the development and implementation of imaging tests aimed at directly measuring the presence and burden of subclinical atherosclerosis in diverse vascular beds within individual patients. Such individualized disease assessment clearly trumps risk factors as the strongest predictor of incident CVD events and death [2] . The promising results of incorporating such
more » ... risk information into clinical decision-making has led experts to advance a CVD risk assessment paradigm shift from a risk-factor based model (prediction) to an atherosclerosis imaging-based approach (disease detection). Among available imaging modalities, coronary artery calcium (CAC) using non-contrast computed tomography is considered one of the most powerful tools for absolute CVD risk assessment in asymptomatic adults [3] . Notwithstanding its essential limitation for ruling out the presence of early non-calcified plaque, CAC has a very high sensitivity for the detection of clinically relevant coronary atherosclerosis in asymptomatic adults [4] , which results in a high negative predictive value. Moreover, CAC appears particularly valuable as a prognostic test. Beyond its well-known ability to identify those individuals more likely to have CVD events independent of traditional risk scoring, population studies and large clinical cohorts have shown asymptomatic subjects with zero CAC (CAC ¼ 0) to have an excellent cardiovascular prognosis regardless of their age, sex, ethnic group, and burden of traditional risk factors [5] . Thus, CAC ¼ 0 stands as perhaps the most powerful negative risk factor for near-and mid-term development of coronary events in asymptomatic adults [6] . In a context of population aging and cost-constrained healthcare systems, the accurate identification of "who not to treat" has important public health implications and may lead to large cost savings [7] . Hence, the clinician will find a CAC ¼ 0 particularly informative in the context of CVD risk assessment of asymptomatic subjects considered at "intermediate" risk by traditional risk scores (where therapeutic decision-making is commonly uncertain). Nonetheless, in order to build decision-making around CAC results that might lead to withholding or reducing preventive pharmacotherapies, the clinician requires reliable information regarding the stability of that CAC ¼ 0 over time: i.e., the "warranty period" of that result, during which it is safe to assume that the patient is likely to have persistent CAC ¼ 0, remaining at low risk for CVD events and not in need for further interventions or repeat CAC evaluation. Indeed aging, and thus a longer exposure to risk factors, may lead to the development of coronary atherosclerosis and calcifications in individuals with initial CAC ¼ 0. Previous studies have reported low conversion rates to CAC > 0 after 4e5 years of follow-up (z20%, including 1% conversion rates to CAC > 100) [8] and very low CVD event rates [5, 9] in subjects with CAC ¼ 0. Nevertheless, uncertainty regarding when and in which patients this conversion and subsequent risk shift will occur has hampered incorporation of CAC ¼ 0 into clinical guidelines, leading to the continuation of costly treatments with potential side-effects in those unlikely to have events, "just in case". 1. Defining the warranty period of CAC ¼ 0: a multidimaging approach The multi-imaging approach, rooted in the systemic nature of atherosclerosis [10] and the heterogeneity by which it affects different vascular beds, integrates the information provided by complementary, non-invasive diagnostic tests. This approach has been tested for further refining absolute CVD risk assessment beyond CAC in specific subgroups [11] , and has recently been DOI of original article: http://dx.
doi:10.1016/j.atherosclerosis.2014.10.084 pmid:25461731 fatcat:qn5hb2o6t5elhhhodcpjkhodk4