A marker of coronary atherosclerosis and can be used to predict cardiovascular disease events.
A coronary artery calcium (CAC) scan is an excellent noninvasive test to diagnose cardiovascular disease and predict its long-term outcome.
Subclinical atherosclerosis, is identified by the presence of coronary artery calcification and progresses over time and can predict the development of coronary heart disease events.
Marker of subclinical coronary artery disease and a noninvasive measure of the calcified component of atherosclerotic plaque of the coronary vessels.
A direct measure of the burden of coronary artery disease.
Coronary artery calcification scan represents noninvasive virtual coronary biopsy to identify vulnerable patients for coronary artery disease.
The major use of coronary calcium scoring is the guide the decision to initiate statin therapy for primary prevention of atherosclerotic disease.
Guidelines suggest starting statin therapy when the 10 year risk for atherosclerotic disease events is 7.5% or greater.
Statin therapy is not recommended for patients at low risk, while intermediate risk patients are potential candidates.
Coronary artery calcium testing may not require a physician order, is non invasive, and the dose of radiation is relatively low similar mammography, high likelihood of improved risk assessment, has excellent predictive value for atherosclerotic cardiovascular disease and mortality and clinical medical intervention.
Coronary artery calcifications are almost always found within atherosclerotic plaques therefore a positive coronary artery calcification score directly identifies the presence of coronary artery disease.
Coronary artery calcification scoring is not helpful in screening patients at either very low or high risk for coronary artery disease.
Coronary artery calcium scores of greater than 100 indicate a 10 year risk of greater than 7 1/2%, which justifies aspirin use for primary prevention to reduce first heart attacks in middle-aged man.
Calcium artery calcium scans in middle-aged adults have a relatively low positive yield: approximately 20-25% of non-diabetic individuals age 30-45 years have detectable coronary calcifications.
Screening of symptomatic patients with known coronary artery disease is not helpful.
A calcium score from 1-19 in an asymptomatic patient doubles the patient’s risk of a cardiovascular event.
Risk rises rapidly with each decile, reaching nine fold when the score of greater than 100.
A CAC score of 100 or higher is associated with a favorable risk benefit estimation for aspirin used.
Whereas a CAC score of zero is estimated to confirm net harm from aspirin.
The degree of overall and abdominal obesity, as reflected by increased BMI and waist circumference are important risk factors for the presence of progression of coronary artery calcifications.
In a study of 10,037 symptomatic patients undergoing CT coronary angiography showed the absence of coronary artery calcification did not ruled out the presence of obstructive coronary artery disease, nor did coronary artery scoring and prognostic information provided by risk factors and severity of coronary artery disease (Villines TC et al).The
Risk ratio for a myocardial infarction arrhythmia cardiovascular death in patients with a coronary artery calcification score above the group median is 4.2.
The negative predictive value of a coronary artery calcium (CAC) score of 0 can be as high as 99% and is associated with a 0.1% annual risk of cariovascular events and a 99.4% survival for 10 years (Haberle R, Sarwar A, Budoff MJ).
The absence of calcium does not necessarily mean absence of unstable plaque: Sometimes prior to calcification plaques may cause rupture and acute atherosclerotic disease events.
Linear relationship between the extent of calcification and all-cause mortality.
In general, the absence of coronary calcium signifies a low risk state that is a tenure risk of less than 5%.
Coronary calcification indicates an advanced state of vascular disease.
Coronary artery calcification testing in high-risk elderly individuals as demonstrated approximately 1/3 of zero artery calcium scores (Silverman MG).
Coronary artery CT with lesions of greater than 130 Hounsfield units indicate coronary artery calcification.
CAC score below 100 indicates low risk disease and a score of 300 indicates high risk for coronary disease.
A coronary calcium score of 1-99 Agatston units falls in the borderline-low intermediate risk zones.
MESA Study found coronary calcium scores in the range of 100-299 Agatston units project tenure risk for atherosclerotic disease events of approximately 15%.
In patients with a 300 to a greater Agatston coronary calcium score, the patient is considered high risk and a candidate for high intensity intensity statin therapy with a 10 year risk for atherosclerotic disease of 20% or greater.
Agatston scoring is the most used technique to quantify such calcifications seen on CT and is derived from examining 3 mm thick axial tomograms, identifying coronary artery plaques with calcium, and multiplying the plaque area by a weighting factor, which is determined by the maximum calcium lesion density (Agatson AS).
Educational levels inversely associated with prevalence in early middle age with high risk for individuals with less than a high school education.
In patients with a zero calcium score, only 6.5% have detectable non-calcified plaque by 64-slice computed tomographic coronary angiography.
The Screening for Heart Attack Prevention and Education (SHAPE) guidelines recommend screening of all asymptomatic men 45-75 years of age and asymptomatic women 55-75 years of age except in those defined as very low risk.
Screening with CT scan delivers an effective dose from a single screening from 0.8-10.5 mSv, with median and mean values of 2.3 and 3.1 mSv, respectively (Kim).
For a single CT screening and a median dose of radiation of 2.3 mSv for a 40 year old, it is estimated to result in a lifetime excess cancer risk of 9 and 28 cancers per 100,000 persons for men and women, respectively.
With modern computerized tomography radiation exposure is less than 1 mSv similar to the background radiation of living in Denver for three months.
For a single CT screening for coronary artery calcification for an 80 year old it is associated with a risk of 3 and 6 for men and women per 100,000 persons (Kim).
It is not yet known if screening for CAC will improve cardiovascular outcomes.
CAC has low specificity and has an overall diagnostic accuracy for coronary artery disease of 70%, and is therefore an inadequate single assessment for diagnosing coronary artery disease (O’Rourke R).
In a Framingham study of asymptomatic patients with intermediate risk of major cardiovascular events: the risk of coronary heart disease death or myocardial infarction with a coronary artery calcification score of 0-99 was 0.4% , with a score of 100-399 was 1.3%% and with a score of 400 or greater was 2.4% (Greenland P).
Coronary artery calcium score predicts risk of cardiovascular disease in all ethnic groups.
In a study of 20,000 patient-years indicated that all patients with a Agatson score greater than 100 had a relative risk increase of 9.2 for nonfatal myocardial infarction or death , and those with a score higher than 400 had a relative risk increase of 26.2 (Arad Y).
Agatson score of 0.1-99, 100-399 and 400 or higher, correlated with total cardiovascular events with rates of 0.54%, 1%, 5.5%, and 14%, respectively(Arad Y).
The CAC scan is the best test for classifying intermediate risk patients into appropriate treatment groups.
The CAC score Is a helpful tool to direct statin treatment of coronary atherosclerosis.
The rate of annualized increase in coronary artery calcifications is higher for patients with chronic kidney disease and those on dialysis, than for the general cardiovascular disease population in which renal disease is not present.
Review of 10 trials, the annual rate of coronary artery calcification increase was 17.2%, and this was mildly higher for patients with chronic kidney disease in those receiving dialysis, yet no reproducible treatment effect was noted on the calcification rate (McCullogh PA).
Potential harm of this testing includes radiation exposure, unnecessary interventions, insurability, and alterations in the quality of life with labeling a patient at higher risk, medicalization of asymptomatic individuals and cost.
MESA study of 6814 patients asymptomatic patients with CRP 2 mg/L or more, CRP did not predict coronary events, but CAC stores of more than 100, were strongly predictive of both coronary heart disease, and overal CV events (Blaha MJ et al).