How is CT performed for cardiac assessment?

Updated: Nov 20, 2018
  • Author: Richard S Krause, MD; Chief Editor: Barry E Brenner, MD, PhD, FACEP  more...
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Answer

Calcium deposits are commonly found in atherosclerotic coronary plaques. The total amount of coronary calcium is predictive of future cardiac events. Cardiac computed tomography (CCT) scanning can measure the density and extent of calcifications in coronary artery walls. The technique of CCT was established with electron beam scanners, but it has been refined and made more widely available with the introduction of multidetector scanners. The technique relies on electrocardiographic (ECG) "gating" to compensate for cardiac motion. No contrast is used. The coronary lumen itself is not visualized. A related technique is cardiac CT angiography (CCTA). CCTA uses intravenous (IV) contrast material to provide direct visualization of the coronary lumen. Gating is also used to decrease motion artifact. CCTA has been shown to have good correlation with the criterion standard of conventional coronary angiography.

CCTA techniques are under rapid development. A low and regular heart rate (typically sinus rhythm) is necessary for optimal imaging, and it is often necessary to administer beta-blockers to achieve an adequately low heart rate (approximately 60-65 bpm or less). Studies have shown that if a patient's heart rate can be brought below 60 bpm, only about 3% of coronary segments will be unevaluable by the CCTA, while at 61-65 bpm, over 21% are unevaluable. Obtaining optimal images with the least radiation exposure depends on control of the heart rate. [26]

Test interpretation requires special training and is usually performed by a radiologist or cardiologist.


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