CT Coronary Angiogram

A coronary angiogram performed using a CT scan machine instead of cardiac catheterization is called a CT coronary angiogram. It is also called MSCT (multi-slice CT) or MDCT (multi-detector CT).

The dye or contrast agent is injected through a short cannula inserted into a vein instead of directly into the coronary arteries. Thus the test can be done as an outpatient. As the dye travels through the coronary arteries, the CT scanner moves rapidly around the patient’s chest, taking many X-ray pictures of the heart in a very short time. The computer then uses a software to reconstruct a 3-dimensional image of the heart and its arteries.

In order to get a clear picture of the heart arteries, the heart rate must not be too fast (heart rate of 60 bpm is ideal) and the patient should be able to hold his breath for a few seconds to minimize blurring of the pictures due to movement of the diaphragm. An irregular heart rhythm caused by atrial fibrillation or ectopics may also render the test inaccurate. If the heart rate is too fast, medication to slow the heart rate is administered before the test.

The test can be used to study calcified or hard plaques as well as soft or non-calcified plaques. An estimate of percentage of narrowing of each vessel can be made with this scan, although it is by no means the gold standard.