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Calcium Scoring Adds Little Prognostic Value To Ct Angiography

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Coronary artery calcium (CAC) scoring may no longer be needed for predicting major adverse cardiac events (MACEs) when a 64-section CT angiography is performed, researchers say.

Cardiac imagingLed by Dr. Hyuk-Jae Chang, of the Division of Cardiology Yonsei University College of Medicine in Seoul, the researchers evaluated the prognostic value of CT angiography alone and with coronary artery calcium scoring for predicting major adverse cardiac events (MACEs) including cardiac death or non-fatal myocardial infarction in patients with low risk of coronary artery disease (CAD). The study was published Jan. 28 online ahead of print publication in the journal Radiology.

Coronary CT angiography is better than CAC scoring in predicting MACEs in low-risk patients suspected of having CAD,” the researchers wrote. “Furthermore, the current standard multisection CT protocol (coronary CT angiography combined with CAC scoring) has no incremental prognostic value compared with coronary CT angiography alone.”

The amount of calcium inside the walls of coronary arteries is a good predictor of future cardiovascular events. The score is derived as a compilation of the size and brightness of all the calcium deposits seen within coronary arteries. A normal CAC score is 0, meaning no calcium is seen, and ranges to over 400. Scores over 80 are associated with an increased likelihood of coronary disease, regardless of classic risk factors.

Current guidelines state that the CAC test is of limited value in people at low risk of CAD events; however, for individuals at intermediate CAD risk, coronary calcium scoring is considered to provide incremental risk prediction that can help guide therapy. Currently, performing both CAC scoring and coronary CT angiography in combination is the conventional protocol for diagnostic evaluation of CAD. This study adds to the evidence that CAC may be of little value in predicting outcomes for these patients. Given recent concerns about radiation exposure associated with cardiovascular imaging, eliminating CAC would help reduce radiation exposure.

The reported study involved 4,338 patients at a single institution who underwent 64-section CT for evaluation of suspected CAD, using both CAC scoring and CT angiography. The tests were performed concurrently using standard scanning protocols. Patients were over 30 years old and the average age was 60. None had prior documented CAD. A total of 359 patients who had elective revascularization within 60 days of the CT scan were excluded from the analysis.

Patients were followed for more than two years using phone interviews recording major adverse cardiac events, including cardiac deaths or non-fatal myocardial infarctions. The data was analyzed using multivariable Cox proportional hazards models to predict MACEs. Risk-adjusted models incorporated traditional risk factors for CAC scoring and coronary CT angiography. CAC data and coronary CT angiograms were evaluated by using a Wizard workstation by Siemens Medical Solutions.

The researchers divided CAC scores into five groups, those with a score of 0, 1-10, 11-100, 101-400 and over 400. CT scan results were categorized into one, two and three-vessel disease, defined as greater than 50 percent stenosis.

During the average follow-up of 828 days (27.6 months), there were 105 major adverse coronary events, for a 3 percent event rate. The presence of obstructive CAD at coronary CT angiography was independently predictive of MACE, and the prognostic value increased according to the number of vessels with stenosis.

Using a receiver operating characteristic curve (ROC) analysis, the researchers found coronary CT angiography was superior to CAC scoring as shown by a significantly greater area under the ROC curve (AUC) (0.892 vs 0.810, P < .001).  By contrast, no significant incremental value for the addition of CAC scoring to coronary CT angiography was found. (AUC = 0.892 for coronary CT angiography alone vs 0.902 with addition of CAC scoring, P = .198).

“In the multisection CT era, coronary CT angiography is better than coronary artery calcium scoring in predicting major adverse coronary events in low-risk patients suspected of having coronary artery disease,” the researchers conclude. “Furthermore, the current standard multisection CT protocol (coronary CT angiography combined with CAC scoring) has no incremental prognostic value over coronary CT angiography alone in such individuals. Therefore, in terms of prognosis, coronary artery calcium scoring may no longer need to be incorporated into the cardiac CT protocol in this population, considering the radiation exposure.”

By: Michael O'Leary, contributing editor Health Imaging Hub


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