Specific patterns of calcifications, namely shell like and diffuse were shown to be more associated with severe stenosis rather than a nodular pattern ( 9). The radiation dose is low, with a typical effective dose of 70% in at least one coronary artery with high sensitivity and specificity ( 8). CAC is typically scanned in a prospectively ECG-triggered mode with 2.5-3.0 mm thick axial images. The mass score has also been advocated, with less inter-scanner variability, however limited outcome data is available with this measure, so it is rarely used. In contrast to the Agatston score, the calcium volume score (CVS) represents an actual volume of CAC and reduces variability between scans ( 5) opposed to the increase in Agatston score which might just represent an increase in plaque attenuation rather than size over time. Because of the stepwise nature of the density factor, changes in the Agatston score might not accurately capture changes in coronary calcium. The Agatston score is calculated by multiplying the lesion area (mm 2) by a density factor (between 1 and 4) ( 4). Baseline CAC has been quantified by several methods. However, MDCT have the advantage of higher spatial resolution and image quality especially with recent scanner generations, but optimally should be done with heart rate control to limit motion artifacts from high heart rates.ĬAC is defined as a hyper-attenuating lesion >130 Hounsfield units with an area of ≥3 pixels. Electron beam computed tomography allowed faster imaging with higher temporal resolution. Formerly, electron beam computed tomography (EBCT) and more recently multidetector computed tomography (MDCT) have been used for this evaluation. Two modes of cardiac CT are used for CAC quantification. In this paper we will review some of the established technical facts and clinical applications of CAC Scoring together with some of the controversial issues and limitations that might need better understanding and further studies to be better clarified.Ĭalcium scoring imaging modalities and scoring techniques Hence, it was important to look for other imaging modalities as calcium artery calcium (CAC) score to properly assess the cardiovascular risk. The main limitation of FRS, is that it does not incorporate family history and many components of metabolic syndrome. The Framingham risk score (FRS) is probably the most extensively adopted ( 3). Multiple scoring systems have been developed to predict the risk of coronary events in patients who do not have a history of cardiovascular diseases. There is a clinical dilemma, in that almost half of acute coronary events occur in previously asymptomatic patients ( 1), and nearly 70% of acute coronary events result from coronary lesions that are not flow-limiting before the event ( 2). Accepted for publication Jun 11, 2012.Ītherosclerotic cardiovascular disease is number one cause of death in the world, accounting for nearly one-third of all deaths worldwide. Keywords: Coronary artery calcium coronary artery disease calcium score cardiovascular risk Accordingly, more studies need to be conducted to further help understand the ideal way to utilize this imaging tool and decreasing downstream utilization. However, statin did not consistently prove beneficial in slowing the CAC progression rate, but did reduce CV events significantly in patients with increased CAC. Studies also demonstrated that risk assessment using CAC was motivational to patients leading to better adherence to their preventive practices as well as medications. Unanswered questions include the concept of CAC progression that need to be standardized with respect to technique, interpretation and subsequent management strategies. Having a zero calcium score is currently used in United Kingdom practice guidelines (NICE) as a gatekeeper for any further investigations in patients presenting to the emergency department (ED) with chest pain. Higher risk groups like patients with diabetes, a higher prevalence of CAC has been shown to impart a high short term risk of CV events, while those with zero calcium score had excellent event-free survival, similar to non-diabetic patients. Furthermore, it significantly reclassifies moderate risk patients into lower or higher risk categories. It has been shown to have a superior role predicting future cardiac events and survival rates when combined with other traditional risk factor scoring systems as Framingham risk score (FRS). Abstract: Coronary artery calcification (CAC) is a widely used imaging modality for cardiovascular risk assessment in moderate risk patients.
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