Introduction:

CT coronary angiography is a modern form of non-invasive angiography that takes X-ray pictures of cross-sections of the heart (like slices of bread) very quickly. These images are re-assembled by the computer to produce a detailed picture of the heart. It is 'non-invasive' because the body is not physically entered, except for a drip (small plastic tube) inserted into an arm vein to give the contrast (dye). CT angiography can give information about narrowings, fat deposits and calcium in the arteries of the heart, about heart muscle function, about heart valves, and about the pericardial sac that encloses the heart.

How is CT angiography different from conventional coronary angiography?

Conventional coronary angiography is carried out by inserting a small tube ('catheter') into an artery in the groin or wrist, and passing it to the heart. The tip of the catheter rests in the coronary artery to be imaged, and the contrast (dye) is injected directly into the artery while an x-ray 'movie' of the heart is taken. The contrast is seen on the 'movie' outlining the inside of the artery.

Conventional coronary angiography has the disadvantage of being invasive, which introduces some risks that CT angiography does not have. Both CT and conventional angiography use contrast agents (dyes) and these have some risk of allergy. Both tests also use x-rays with a consequent small risk related to the radiation exposure. CT angiography is very good at ruling out coronary disease and is better at showing the extent of plaque but conventional angiography is better at showing the severity of narrowings especially when the arteries contain a lot of calcium. Treatment of narrowings (angioplasty or PCI) may be possible at the same time as conventional angiography, but not with CT angiography.

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