Electron-beam computed tomography screening for asymptomatic coronary artery disease

Genetics of Subclinical Coronary Atherosclerosis

Purpose of Review

This review highlights recent findings regarding genetics of coronary artery calcification (CAC), a marker of subclinical atherosclerosis burden, that is a precursor of clinical coronary artery disease.

Recent findings

CAC quantity is heritable. Genome wide association studies of common single nucleotide polymorphisms have identified genomic regions explaining ~2.4% of CAC heritability. Low frequency and rare variants explain additional variation in CAC. Evidence suggests that there may be different genetic etiologies for variation in CAC progression than for cross-sectional measures of CAC. Studies integrating multiple -omics data are providing new insights into the pathobiology of subclinical coronary atherosclerosis.

Summary

The future is promising for innovative studies utilizing whole genome sequencing data as well as other -omics such as epigenomic modifications of genes and gene expression. These studies may provide multiple sources of data pointing to the same gene or pathway, thus providing greater confidence in findings.

Early subclinical coronary artery calcification in young adults who were pediatric kidney transplant recipients

Coronary artery disease (CAD) is the leading cause of death in adults after successful kidney transplantation. Children who have undergone successful kidney transplantation are entering young adulthood; however, the prevalence and extent of CAD in this population is unknown. We conducted a pilot study in young adults with stable allograft function, who received kidney transplants as children to measure coronary artery calcification (CAC), a marker of coronary artery atherosclerosis and CAD. We evaluated 19 young adults after successful pediatric kidney transplantation for known CAD risk factors; these patients underwent noninvasive imaging with electron-beam computed tomography (EBCT) for measurement of CAC. Prevalence and quantity of CAC were then compared to asymptomatic individuals from the community. All patients had multiple risk factors for CAD. Mean age at evaluation was 32 years (range: 21-48 years). CAC is uncommon in individuals in the community in this age range; however, nearly half of our patients had CAC detected with the quantity of CAC comparable to asymptomatic individuals from the community 10-40 years older. These data suggest young adults who received pediatric kidney transplants are at increased risk for developing early CAC and need close monitoring to detect early CAD so as to prevent premature cardiac morbidity and mortality.

Age-dependent associations between blood pressure and coronary artery calcification in asymptomatic adults

OBJECTIVE

The age-dependent roles of the components of blood pressure (BP) in the development of coronary artery calcification (CAC) are poorly understood.

DESIGN

We examined systolic (SBP), diastolic (DBP), mean arterial pressure (MAP) and pulse pressure (PP) as predictors of CAC in 830 asymptomatic, non-diabetic participants in a community-based study who were aged > or = 30 years and free of antihypertensive therapy or known cardiovascular disease.

METHODS

CAC was measured with electron beam computed tomography. Tobit regression was used in two age groups (< 50 years and > or = 50 years) to evaluate the relationship of BP components with presence and quantity of CAC, adjusting for traditional coronary artery disease (CAD) risk factors.

RESULTS

Among those aged < 50 years, CAC was positively associated with SBP, DBP and MAP, considering each pressure individually and DBP was the strongest predictor (P = 0.0088). Among those aged > or = 50 years, CAC was positively associated with SBP (P = 0.0257) and PP (P = 0.0028), considered individually. When SBP and DBP were in the same model, presence and CAC quantity were positively associated with SBP (P = 0.0024) and negatively with DBP (P = 0.0401), favoring PP as the best predictor of CAC.

CONCLUSIONS

SBP, DBP and PP have age-dependent roles in the prediction of CAC similar to their roles in prediction of future CAD events. These observations provide new evidence supporting the measurement of CAC as a surrogate of target organ disease and subsequently, as a predictor of increased risk of future CAD events.