Isac Thomas

The evolving view of coronary artery calcium and cardiovascular disease risk

Calcification of the coronary artery is a complex pathophysiologic process that is intimately associated with atherosclerosis. Extensive investigation has demonstrated the value of identifying and quantifying coronary artery calcium (CAC) in atherosclerotic cardiovascular disease (CVD) prognostication. However, over the last several years, an increasing body of evidence has suggested that CAC has underappreciated aspects that modulate, and at times attenuate, future CVD risk. The most commonly used measure of CAC, the Agatston unit, effectively models both higher density and higher area of CAC as risk factors for future CVD events. Recent findings from the Multi‐Ethnic Study of Atherosclerosis (MESA) have challenged this assumption, demonstrating that higher density of CAC is protective for coronary heart disease and CVD events. Statins may be associated with an increase in CAC, an unexpected finding given their clear benefits in the prevention and treatment of CVD. Studies utilizing intracoronary ultrasound and coronary computed tomography angiography have demonstrated that calcified atherosclerotic plaque—as compared with noncalcified or sparsely calcified plaque—is associated with fewer CVD events. These studies lend support to the often‐asserted (but as yet unvalidated) view that calcification may play a role in plaque stabilization. Furthermore, vascular calcification, though a surrogate for atherosclerotic plaque burden, may also possess identifiable aspects that can refine CVD risk assessment.

Greater Volume but not Higher Density of Abdominal Aortic Calcium Is Associated With Increased Cardiovascular Disease Risk: MESA (Multi-Ethnic Study of Atherosclerosis).

Background—Abdominal aortic calcium (AAC) and coronary artery calcium (CAC) independently and similarly predict cardiovascular disease (CVD) events. The standard AAC and CAC score, the Agatston method, upweights for greater calcium density, thereby modeling higher calcium density as a CVD hazard. Methods and Results—Computed tomography scans were used to measure AAC and CAC volume and density in a multiethnic cohort of community-dwelling individuals, and Cox proportional hazard was used to determine their independent association with incident coronary heart disease (CHD, defined as myocardial infarction, resuscitated cardiac arrest, or CHD death), cardiovascular disease (CVD, defined as CHD plus stroke and stroke death), and all-cause mortality. In 997 participants with Agatston AAC and CAC scores >0, the mean age was 66±9 years, and 58% were men. During an average follow-up of 9 years, there were 77 CHD, 118 CVD, and 169 all-cause mortality events. In mutually adjusted models, additionally adjusted for CVD risk factors, an increase in ln(AAC volume) per standard deviation was significantly associated with increased all-cause mortality (hazard ratio=1.20; 95% confidence interval, 1.08–1.33; P<0.01) and an increased ln(CAC volume) per standard deviation was significantly associated with CHD (hazard ratio=1.17; 95% confidence interval, 1.04–1.59; P=0.02) and CVD (hazard ratio=1.20; 95% confidence interval, 1.05–1.36; P<0.01). In contrast, both AAC and CAC density were not significantly associated with CVD events. Conclusions—The Agatston method of upweighting calcium scores for greater density may be inappropriate for CVD risk prediction in both the abdominal aorta and coronary arteries.

Association of cardiovascular disease risk factors with coronary artery calcium volume versus density

Objectives Recently, the density score of coronary artery calcium (CAC) has been shown to be associated with a lower risk of cardiovascular disease (CVD) events at any level of CAC volume. Whether risk factors for CAC volume and CAC density are similar or distinct is unknown. We sought to evaluate the associations of CVD risk factors with CAC volume and CAC density scores. Methods Baseline measurements from 6814 participants free of clinical CVD were collected for the Multi-Ethnic Study of Atherosclerosis. Participants with detectable CAC (n=3398) were evaluated for this study. Multivariable linear regression models were used to evaluate independent associations of CVD risk factors with CAC volume and CAC density scores. Results Whereas most CVD risk factors were associated with higher CAC volume scores, many risk factors were associated with lower CAC density scores. For example, diabetes was associated with a higher natural logarithm (ln) transformed CAC volume score (standardised β=0.44 (95% CI 0.31 to 0.58) ln-units) but a lower CAC density score (β=−0.07 (−0.12 to −0.02) density units). Chinese, African-American and Hispanic race/ethnicity were each associated with lower ln CAC volume scores (β=−0.62 (−0.83to −0.41), −0.52 (−0.64 to −0.39) and −0.40 (−0.55 to −0.26) ln-units, respectively) and higher CAC density scores (β= 0.41 (0.34 to 0.47), 0.18 (0.12 to 0.23) and 0.21 (0.15 to 0.26) density units, respectively) relative to non-Hispanic White. Conclusions In a cohort free of clinical CVD, CVD risk factors are differentially associated with CAC volume and density scores, with many CVD risk factors inversely associated with the CAC density score after controlling for the CAC volume score. These findings suggest complex associations between CVD risk factors and these components of CAC.

Alcohol Consumption and Cardiac Disease: Where Are We Now?

I n this issue of the Journal, Whitman et al. (1) evaluated a statewide database of ambulatory surgery, emergency, or inpatient care visits. Their exposure variable was a diagnosis of alcohol abuse, and they found that each of their 3 outcome variables, atrial fibrillation (AF), myocardial infarction (MI), and congestive heart failure (CHF), was significantly increased in alcohol abusers. The data indicate that alcohol abuse is a powerful cardiac risk factor, one of the strongest for AF and at least equivalent to established risk factors for MI and CHF. The authors are to be commended for carefully differentiating between the relative risk and absolute risk of alcohol abuse—both individually and in combination with other risk factors—as such differences have clinical implications.

Density of calcium in the ascending thoracic aorta and risk of incident cardiovascular disease events

BACKGROUND AND AIMS The volume and density of coronary artery calcium (CAC) both independently predict cardiovascular disease (CVD) beyond standard risk factors, with CAC density inversely associated with incident CVD after accounting for CAC volume. We tested the hypothesis that ascending thoracic aorta calcium (ATAC) volume and density predict incident CVD events independently of CAC. METHODS The Multi-Ethnic Study of Atherosclerosis (MESA) is a prospective cohort study of participants without clinical CVD at baseline. ATAC and CAC were measured from baseline cardiac computed tomography (CT). Cox regression models were used to estimate the associations of ATAC volume and density with incident coronary heart disease (CHD) events and CVD events, after adjustment for standard CVD risk factors and CAC volume and density. RESULTS Among 6811 participants, 234 (3.4%) had prevalent ATAC and 3395 (49.8%) had prevalent CAC. Over 10.3 years, 355 CHD and 562 CVD events occurred. One-standard deviation higher ATAC density was associated with a lower risk of CHD (HR 0.48 [95% CI 0.29-0.79], p<0.01) and CVD (HR 0.56 [0.37-0.84], p<0.01) after full adjustment. ATAC volume was not associated with outcomes after full adjustment. CONCLUSIONS ATAC was uncommon in a cohort free of clinical CVD at baseline. However, ATAC density was inversely associated with incident CHD and CVD after adjustment for CVD risk factors and CAC volume and density.

Progression of calcium density in the ascending thoracic aorta is inversely associated with incident cardiovascular disease events.

Aims Little is known regarding the risk of atherosclerotic cardiovascular disease (ASCVD) conferred by changes in the volume and density of ascending thoracic aorta calcium (ATAC) over time. We evaluated changes in ATAC volume and density scores and incident ASCVD events. Methods and results The Multi-Ethnic Study of Atherosclerosis is a prospective cohort study of individuals without baseline clinical ASCVD. Ascending thoracic aorta calcium was measured from baseline and follow-up (mean interval 2.4 years) cardiac computed tomography (CT). Cox proportional hazard regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) per standard deviation for events after the follow-up exam adjusted for ASCVD risk factors, baseline ATAC and coronary artery calcium (CAC) volume and density, and changes in CAC volume and density. Among 5887 participants, 296 (5.0%) had detectable ATAC at baseline, follow-up, or both exams. A total of 403 events occurred over 9.5 years. An increase in ATAC volume was associated with coronary heart disease (CHD) (HR 1.90, 95% CI 1.14-3.16), ASCVD (HR 1.93, 95% CI 1.26-2.94), and ischaemic stroke (HR 2.14, CI 1.21-3.78). An increase in ATAC density was inversely associated with CHD (HR 0.29, 95% CI 0.14-0.60) and ASCVD (HR 0.42, 95% CI 0.23-0.76), but not stroke (HR 0.61, CI 0.23-1.61). Conclusion Ascending thoracic aorta calcium is uncommon on serial cardiac CT. However, changes in ATAC volume and density are both associated with incident ASCVD events, but in opposite directions. Serial assessments in those with baseline ATAC may provide insight into an individuals trajectory of ASCVD risk.

Thoracic Aorta Calcification and Noncardiovascular Disease–Related Mortality: The Multi-Ethnic Study of Atherosclerosis

Objective— Arterial calcification is highly correlated with underlying atherosclerosis. Arterial calcification of the thoracic aorta is evident in many older individuals at high susceptibility to aging-related diseases and non-cardiovascular disease (CVD)–related mortality. In this study, we evaluated the association of thoracic aorta calcification (TAC) with non-CVD morbidity and mortality. Approach and Results— We analyzed data from participants in the Multi-Ethnic Study of Atherosclerosis, a prospective cohort study of subclinical atherosclerosis, in which participants underwent cardiac computed tomography at baseline and were followed longitudinally for incident CVD events and non-CVD events. Using modified proportional hazards models accounting for the competing risk of CVD death and controlling for demographics, CVD risk factors, coronary artery calcium, and CVD events, we evaluated whether TAC was independently associated with non-CVD morbidity and mortality. Among 6765 participants (mean age, 62 years), 704 non-CVD deaths occurred for a median follow-up of 12.2 years. Compared with no TAC, the highest tertile of TAC volume was associated with a higher risk of non-CVD mortality (hazard ratio, 1.56; 95% confidence interval, 1.23–1.97), as well as several non-CVD diagnoses, including hip fracture (2.14; 1.03–4.46), chronic obstructive pulmonary disease (2.06; 1.29–3.29), and pneumonia (1.79; 1.30–2.45), with magnitudes of association that were larger than for those of coronary artery calcium. Conclusions— TAC is associated with non-CVD morbidity and non-CVD mortality, potentially through a pathway that is unrelated to atherosclerosis. TAC may be a general marker of biological aging and an indicator of increased risk of non-CVD and death.

Greater Volume but not Higher Density of Abdominal Aortic Calcium Is Associated With Increased Cardiovascular Disease RiskCLINICAL PERSPECTIVE

Background—Abdominal aortic calcium (AAC) and coronary artery calcium (CAC) independently and similarly predict cardiovascular disease (CVD) events. The standard AAC and CAC score, the Agatston method, upweights for greater calcium density, thereby modeling higher calcium density as a CVD hazard. Methods and Results—Computed tomography scans were used to measure AAC and CAC volume and density in a multiethnic cohort of community-dwelling individuals, and Cox proportional hazard was used to determine their independent association with incident coronary heart disease (CHD, defined as myocardial infarction, resuscitated cardiac arrest, or CHD death), cardiovascular disease (CVD, defined as CHD plus stroke and stroke death), and all-cause mortality. In 997 participants with Agatston AAC and CAC scores >0, the mean age was 66±9 years, and 58% were men. During an average follow-up of 9 years, there were 77 CHD, 118 CVD, and 169 all-cause mortality events. In mutually adjusted models, additionally adjusted for CVD risk factors, an increase in ln(AAC volume) per standard deviation was significantly associated with increased all-cause mortality (hazard ratio=1.20; 95% confidence interval, 1.08–1.33; P<0.01) and an increased ln(CAC volume) per standard deviation was significantly associated with CHD (hazard ratio=1.17; 95% confidence interval, 1.04–1.59; P=0.02) and CVD (hazard ratio=1.20; 95% confidence interval, 1.05–1.36; P<0.01). In contrast, both AAC and CAC density were not significantly associated with CVD events. Conclusions—The Agatston method of upweighting calcium scores for greater density may be inappropriate for CVD risk prediction in both the abdominal aorta and coronary arteries.

Greater Volume but not Higher Density of Abdominal Aortic Calcium Is Associated With Increased Cardiovascular Disease RiskCLINICAL PERSPECTIVE: MESA (Multi-Ethnic Study of Atherosclerosis)

Background—Abdominal aortic calcium (AAC) and coronary artery calcium (CAC) independently and similarly predict cardiovascular disease (CVD) events. The standard AAC and CAC score, the Agatston method, upweights for greater calcium density, thereby modeling higher calcium density as a CVD hazard. Methods and Results—Computed tomography scans were used to measure AAC and CAC volume and density in a multiethnic cohort of community-dwelling individuals, and Cox proportional hazard was used to determine their independent association with incident coronary heart disease (CHD, defined as myocardial infarction, resuscitated cardiac arrest, or CHD death), cardiovascular disease (CVD, defined as CHD plus stroke and stroke death), and all-cause mortality. In 997 participants with Agatston AAC and CAC scores >0, the mean age was 66±9 years, and 58% were men. During an average follow-up of 9 years, there were 77 CHD, 118 CVD, and 169 all-cause mortality events. In mutually adjusted models, additionally adjusted for CVD risk factors, an increase in ln(AAC volume) per standard deviation was significantly associated with increased all-cause mortality (hazard ratio=1.20; 95% confidence interval, 1.08–1.33; P<0.01) and an increased ln(CAC volume) per standard deviation was significantly associated with CHD (hazard ratio=1.17; 95% confidence interval, 1.04–1.59; P=0.02) and CVD (hazard ratio=1.20; 95% confidence interval, 1.05–1.36; P<0.01). In contrast, both AAC and CAC density were not significantly associated with CVD events. Conclusions—The Agatston method of upweighting calcium scores for greater density may be inappropriate for CVD risk prediction in both the abdominal aorta and coronary arteries.