Cardiac computed tomography

Cardiac CT is a frequently performed modality for the evaluation of coronary artery disease. Commonly used techniques include coronary CT angiography and calcium scoring.

A beta blocker and nitrate are usually given beforehand. The beta blocker reduces the heart rate to the ideal 60 bpm, while the nitrate dilates the coronary arteries, improving visualisation.

Cardiac CT can be “coupled” to an ECG so that it only takes pictures during the same part of the cardiac cycle. This reduces noise made from movement of the heart.

Coronary CT angiography

Coronary CT angiography is a non-invasive alternative to invasive coronary angiography, used for the diagnosis of coronary artery disease in those at low or intermediate pretest probability. Those with high pretest probability proceed directly to invasive coronary angiography, as this allows for percutaneous coronary intervention of any stenoses in the same setting. Coronary CT angiography is ECG-coupled.

Calcium scoring

Calcium scoring refers to using non-contrast CT to evaluate the amount of calcium in the coronary artery walls, giving a coronary artery calcium (CAC) score. Calcium scoring can be performed during the non-contrast phase of coronary CT angiography or separately. The score is called Agatston score.

Calcium scoring is used in those with intermediate pretest probability for coronary artery disease. It gives a score which represent different severity of coronary artery disease:

Agatston score	Coronary artery disease severity
0	No coronary artery disease
1-10	Minimal
11-100	Mild
101-400	Moderate
>400	Severe