Rationale and design of the coronary artery calcium consortium: A multicenter cohort study

Abstract

Background Although coronary artery calcium (CAC) has been investigated for over two decades, there is very limited data on the association of CAC with cause of death. The CAC Consortium is a large ongoing multi-center observational cohort of individuals who underwent non-contrast cardiac-gated CAC testing and systematic, prospective, long-term follow-up for mortality with ascertainment of cause of death. Methods Four participating institutions from three states within the US (California, Minnesota, and Ohio) have contributed individual-level patient data to the CAC Consortium (spanning years 1991 to 2010). All CAC scans were clinically indicated and physician-referred in patients without a known history of coronary heart disease. Using strict inclusion and exclusion criteria to minimize missing data and to eliminate non-dedicated CAC scans (i.e. concomitant CT angiography), a sharply defined and well-characterized cohort of 66,636 patients was assembled. Mortality status was ascertained using the Social Security Administration Death Master File and a validated algorithm. In addition, death certificates were obtained from the National Death Index and categorized using ICD (International Classification of Diseases) codes into common causes of death. Results Mean patient age was 54 ± 11 years and the majority were male (67%). Prevalence of CVD risk factors was similar across sites and 55% had a <5% estimated 10-year atherosclerotic cardiovascular disease (ASCVD) risk. Approximately 45% had a Calcium score of 0 and 11% had an Agatston Score ≥400. Over a mean follow-up of 12 ± 4 years, there were 3,158 deaths (4.15 per 1000 person-years). The majority of deaths were due to cancer (37%) and CVD (32%). Most CVD deaths were due to CHD (54%) followed by stroke (17%). In general, CAC score distributions were similar across sites, and there were similar cause of death patterns. Conclusions The CAC Consortium is large and highly generalizable data set that is uniquely positioned to expand the understanding of CAC as a predictor of mortality risk across the spectrum of disease states, allowing innovative modeling of the competing risks of cardiovascular and non-cardiovascular death.

All-cause and cause-specific mortality in individuals with zero and minimal coronary artery calcium: A long-term, competing risk analysis in the Coronary Artery Calcium Consortium

“…The characteristics of the CAC Consortium have been described elsewhere [16][17][18]. Briefly, this was a multi-center, retrospective cohort study of 66,636 consecutive individuals undergoing clinical CAC scoring for CVD risk assessment purposes in 4 high-volume US centers.…”

“…All participants were free of established CVD at cohort entry, defined as the date of the baseline CAC examination. Baseline data including demographic characteristics, cardiovascular risk factors, and baseline CAC scores were obtained at cohort entry between 1991 and 2010, and follow-up information was obtained through June 2014 [16]. For the present analysis, all 66,363 individuals from the CAC Consortium were included.…”

“…In each center, data on self-reported cardiovascular risk factors, treatment use, and laboratory test results were collected as part of the routine clinical visit associated with the referral for CAC testing and/or from a semi-structured in-person interview. Details on the definitions used for each cardiovascular risk factor [16][17][18] are summarized in the Supplementary Methods.…”

“…Mortality was assessed via linkage of patient records with the Social Security Administration Death Master File using a previously validated algorithm [16]. Death certificates were obtained from the National Death Index, and the underlying cause of death was categorized into common causes of death using the International Classification of Diseases, versions 9 and 10 codes as previously described [16].…”

“…Given the complicated association of CAC with risk of multiple diseases, we sought to conduct a competing risk analysis studying zero and minimal CAC within the CAC Consortium, a large cohort with long follow-up for cause-specific death [16]. Such data may be important for estimating prognosis and informing preventive strategies among individuals at the low end of the risk spectrum.…”