冠状动脉钙化的研究进展

冠状动脉钙化（CAC）是动脉粥样硬化的特异性标志,也是粥样斑块负荷程度的标志。冠脉钙化程度与冠脉管腔狭窄程度存在一定相关性,冠脉钙化对心血管疾病的发病率和死亡率具有独立影响。随着各种无创心血管检查技术的进步,冠状动脉钙化的检测和度量更为精确可靠,因此,对冠状动脉钙化的研究有利于早期针对亚临床动脉粥样硬化的干预。     

Coronary artery calcium and its relationship to coronary artery disease

Electron-beam computed tomography (EBCT) and the recent generation of multi-slice computed tomography scanners (MSCT) permit high-resolution imaging of the beating heart and the coronary arteries. The visualization of coronary calcium offers the opportunity to non-invasively obtain direct information on coronary anatomy and plaque burden. For clinical purposes, coronary calcium represents the presence of arteriosclerotic plaques. Coronary calcium is deposited in an actively regulated process related to lipid content of and apoptosis within coronary plaques. The amount of coronary calcium is related to the extent of coronary plaque disease, which has substantial diagnostic and prognostic implications. Visualization of coronary calcium by cardiac CT allows to non-invasively detect and localize coronary plaques and describe their distribution in the coronary tree. Approximately 50% to 70% of all plaques are calcified. Calcium cannot be used to reliably identify plaques at risk for developing complications such as rupture or erosion with ensuing thrombus formation. However, data are accumulating that indicate that calcium is an indicator of coronary arteriosclerotic disease activity. A scan negative for coronary calcium has a high negative predictive value indicating absence of stenotic coronary artery disease and an excellent short- to mid-term prognosis. Studies using serial CT scans indicate that the annual progression of coronary calcium varies between 30% to 50% in symptomatic or high-risk individuals and 0% to 20% in patients treated effectively with lipid-lowering medication. An increased rate of progression of coronary calcium seems to indicate a substantially increased risk for adverse cardiac events.     

Incident coronary artery calcium among postmenopausal women

Recent studies have shown that individuals with 0 coronary artery calcium (CAC) scores have very low risk of coronary heart disease. In the Healthy Women Study, we evaluated development of new CAC among postmenopausal women (n = 272) over a 6-year period, age 62 at the 1st and 68 at the 3rd electron beam tomography (EBT) examination. At the 1st EBT, 155 of 272 (57%) women had 0 CAC. By the 3rd, 56 (36%) of these women had developed new CAC, including 38 with ≥5 Agatston units. There was practically no regression from having CAC at the 1st EBT to no CAC at the 3rd EBT. The risk of developing new CAC over 6 years among women with 0 CAC on their 1st EBT was strongly and significantly related to presence of both aortic calcium and carotid plaque at the time of 1st EBT. Baseline premenopausal risk factors, age 47, apolipoprotein B, body mass index (BMI) and triglycerides, were significant predictors of incident CAC as were the changes in BMI and low density lipoprotein cholesterol between premenopause and the 1st post exam, age 53. Risk factors measured premenopause and change in risk factors from premenopause to the 1st post exam and the extent of subclinical disease in other vascular beds are primary determinants of the risk of developing incident CAC in women over a 6-year period.     

Epidemiologic guidance with coronary artery calcium scoring

The importance of screening for subclinical coronary artery disease is reinforced by the detection gap existing between the currently used risk stratification tools and the persistently elevated rates of cardiovascular disease in Western countries. Medicare data clearly indicate the extremely high cost of caring for patients with end-stage diseases, and early detection may curb some of these expenses. Coronary artery calcium screening has become a widely used tool to estimate risk in a variety of categories in the general population and is discussed in this review.     

Coronary artery calcium and cardiovascular risk in diabetes

Measurement of coronary artery calcium score (CACS) by electron beam tomography has been shown to a powerful predictor of coronary heart disease events in asymptomatic non-diabetic subjects. In type 2 diabetes, measurement of CACS was found to be a powerful predictor of cardiovascular events which could enhance prediction provided by established risk models. 23% of type 2 diabetic subjects with low CACS were found to be at low risk for cardiovascular events. Moreover mortality was similar for type 2 diabetic and non-diabetic subjects with undetectable coronary artery calcification. Conversely type 2 diabetic subjects with high CACS were identified who were at high cardiovascular risk. Thus not all those with type 2 diabetes are at similar cardiovascular risk. Measurement of CACS enables cardiovascular risk in type 2 diabetes to be stratified so that the level of preventive therapy could be reduced in some and intensified in others. Although prospective data for the power of CACS to predict CHD events in type 1 diabetes are lacking, measurement of CACS could help in deciding on preventive therapy in type 1 diabetes.     

Coronary artery calcium testing: dos and don'ts

Measurement of traditional risk factors remains the foundation of current clinical practice guidelines when screening for coronary heart disease (CHD) risk. However, many adults who experience CHD events are not identified as higher risk based on their traditional risk factors. Observational data show that the coronary artery calcium (CAC) score improves risk prediction, even after taking into account traditional risk factors. The authors have outlined several principles of CAC testing into a list of dos and don'ts to help maximize its potential benefit while minimizing potential harm.     

Coronary artery calcium score:Re-evaluation of its predictive value for coronary artery disease

Coronary artery disease is the leading cause of death in advanced countries and its prevalence is increasing among the developing countries.Cardiac computed tomography(CT) has been increasingly used in the diagnosis of coronary artery disease due to its rapid improvements in multislice CT scanners over the last decade,and this less-invasive technique has become a potentially effective alternative to invasive coronary angiography.Quantifying the amount of coronary artery calcium with cardiac CT has been widely accepted as a reliable non-invasive technique for predicting risk of future cardiovascular events.However,the main question that remains uncertain is whether routine,widespread coronary artery calcium scoring in an individual patient will result in an overall improvement in quality of care and clinical outcomes.In this commentary,we discuss a current issue of the clinical value of coronary artery calcium scoring with regard to its value of predicting adverse cardiac events.We also discuss the applications of coronary artery calcium scores in patients with different risk groups.     

冠状动脉钙化与急性心肌梗死的关系简

目的 探讨冠状动脉钙化与急性心肌梗死之间的关系.方法 22 537例患者中,男13 204例,女9 333例,年龄（58.53±9.48）岁,共有急性心肌梗死患者2 254例.依据冠状动脉造影术中能否发现冠状动脉钙化分为钙化组（A组）和无钙化组（B组）,统计两组间心肌梗死发病率的区别,并探讨其原因.结果 钙化组心肌梗死患病率明显高于无钙化组,差异有统计意义（18.16％vs.8.84％,P＜0.001）;钙化组较无钙化组男性多见（62.46％ vs.58.04％,P＜0.001）、年龄偏大[（64.61±7.92）岁vs.（57.67±9.37）岁,P＜0.001];糖尿病（25.64％ vs.15.28％,P＜0.001）、原发性高血压（高血压）发病率高（74.00％vs.57.13％,P＜0.001）;易发生血管病变（93.70％ vs.7.32％,P＜0.001）,且以多支血管病变为主.即使在心肌梗死患者中,钙化组血管病变的发生率及多支血管病变所占比例也超过非钙化组,差异有统计意义（99.61％vs.94.32％,P＜0.05;91.18％ vs.66.23％,P＜0.05）.两组均以ST段抬高型急性心肌梗死为主,两组心肌梗死部位比较,差异无统计学意义（P＞0.05）.结论 冠状动脉钙化患者,男性多见、年龄偏大;糖尿病、高血压发病率高;易发生血管病变,容易导致心肌梗死.     

Renal artery calcium is independently associated with hypertension.

OBJECTIVES: We tested the hypothesis that renal artery calcium (RAC), a marker of atherosclerotic plaque burden, is also significantly associated with higher blood pressure levels and a diagnosis of hypertension. BACKGROUND: In the nonrenal systemic vasculature, atherosclerotic plaque burden has been shown to be significantly associated with hypertension. METHODS: A total of 1,435 consecutive patients were evaluated at a university-affiliated disease prevention center for the extent of calcified atherosclerosis in the systemic vasculature. RESULTS: The overall prevalence of calcium in either renal artery was 17.1%, with men having a significantly higher prevalence (19.0%, 153 of 804) than women (14.7%, 93 of 631) (p = 0.03). After adjustment for age and gender, subjects with a RAC score >0 had a significantly higher prevalence of hypertension (41.2 vs. 29.5, p < 0.01). In a logistic model that adjusted for age, gender, body mass index, percent body fat, diabetes, smoking, dyslipidemia, and the extent of calcified atherosclerosis in the nonrenal vasculature, those with any RAC had a significantly higher odds ratio (1.61, p = 0.01) for hypertension than those with no RAC. CONCLUSIONS: The results of this study suggest that the presence of RAC is associated with higher odds for prevalent hypertension, independent of CVD risk factors and the extent of calcified atherosclerosis in the nonrenal vasculature.     

The prevalence of coronary artery calcium among diabetic individuals without known coronary artery disease

OBJECTIVES: We sought to examine the age and gender distribution of coronary artery calcium (CAC) by diabetes status in a large cohort of asymptomatic individuals. BACKGROUND: Among individuals with diabetes, coronary artery disease (CAD) is a major cause of morbidity and mortality. Electron-beam tomography (EBT) quantifies CAC, a marker for atherosclerosis. METHODS: Screening for CAC by EBT was performed in 30,904 asymptomatic individuals stratified by their self-reported diabetes status, gender, and age. The distribution of CAC across the strata and the association between diabetes and CAC were examined. RESULTS: Compared with nondiabetic individuals (n = 29,829), those with diabetes (n = 1,075) had higher median CAC scores across all but two age groups (women 40 to 44 years old and men and women > or =70 years old). Overall, the likelihood of having a CAC score in the highest age/gender quartile was 70% greater for diabetic individuals than for their nondiabetic counterparts. CONCLUSIONS: Younger diabetic individuals appear to have calcified plaque burden comparable to that of older individuals without diabetes. These findings call for future research to determine if EBT-CAC screening has an incremental value over the current CAD risk assessment of individuals with diabetes.     

Diagnostic and prognostic value of coronary artery calcium screening

PURPOSE OF REVIEW: Algorithms and equations to calculate risk of cardiovascular events, though very useful as an in-office tool to conduct a preliminary assessment demonstrate a limited ability to predict risk in the individual patient. This has favored the development of several imaging modalities for subclinical atherosclerosis such as imaging of coronary calcium by computed tomography. RECENT FINDINGS: Arterial wall calcification is intimately associated with atherosclerosis development and is therefore an optimal marker of the presence of disease. The paradigm underlying the use of imaging technologies to identify subclinical disease is that the quantification of plaque burden may provide a better risk stratification approach for the individual patient than the currently available tools. SUMMARY: The most recent evidence supports this approach as will be discussed in the current review.