CT-based Coronary Angiography is a new, non-invasive alternative for some patients, made possible by the development of high-speed multi-detector CT scanners. The CT scanner acquires imaging data extremely rapidly, which allows selective imaging of the heart in a specific phase of the cardiac cycle while a bolus of contrast agent passes through the arteries. Cardiac gating and short breath-holds ensure that the images are free from motion artifacts. After the data is processed, images can be viewed as cross-sections of the heart, 3-D reconstructions of the heart and coronary arteries, and 3-D reconstructions that appear as planar images along the length of the arteries.
Clinical studies have shown that Coronary CTA is reliable for the non-invasive assessment of stenoses in the proximal and mid regions of the coronary arteries, where the majority of stenoses are found. Clinical studies have shown that both, the sensitivity and specificity, for the detection of clinically significant stenoses are about 90%.
Coronary CTA has some advantages over catheterbbased angiography and these may provide the impetus to establish this procedure as a screening tool:
- Coronary CTA can image blood vessel walls and the anatomy of the heart and can, therefore, be used to assess the pericardium, cardiac chamber size and shape, and to detect ventricular aneurysms.
- Coronary CTA can be used to map the pulmonary veins prior to pulmonary vein ablation for atrial fibrillation or biventricular pacemaker placement.
- Both calcified and non-calcified atherosclerotic plaques can be seen in coronary CTA images and, therefore, it is possible to assess a patient's total calcified and non-calcified plaque burden as high, medium or low. However, it is not yet possible to reliably distinguish between lipid-rich and fibrous plaques, and predict which lesions are more likely to rupture and cause an acute cardiac event.