CT Coronary Angiography to Detect Coronary Artery Disease: low dose radiation in high risk individuals

Coronary atherosclerosis is a frequently encountered chronic disease of the arteries of the heart with very high mortality rates worldwide. It occurs predominantly in individuals with acquired risk factors and a genetic predisposition. Progression of atherosclerosis develops from early asymptomatic stages to advanced stages that may cause cardiac symptoms already starting in the 2nd or 3rd decades in life. In the last one and a half decades Computed Tomography Coronary Angiography (CTCA) has emerged as modality for imaging of the coronary arteries of the heart. A non-enhanced scan shows the total amount of coronary calcium; while a contrast-enhanced CT coronary angiography permits evaluation of narrowing of the vessel lumen as well as detection of both calcified and non-calcified atherosclerotic plaques. Radiation exposure for the patient is inherent to CT technique and the related risk of cancer is of major concern. The average radiation dose of a CTCA has decreased over the years from 20-30 mSv to <3 mSv which is below the dose of nuclear cardiac imaging techniques or conventional invasive coronary angiography Several studies acknowledge the high diagnostic accuracy of CTCA compared to the gold standard invasive coronary angiography. CTCA reliably detects, and especially rules out significant stenosis in stable patients with a low or intermediate pre-test probability of having coronary artery disease (CAD). Besides these direct diagnostic purposes, CTCA has incremental prognostic value over traditional risk factors (i.e. hypertension, diabetes mellitus, smoking, cholesterol blood values etc.) to predict adverse cardiac events in symptomatic patients. Nevertheless clinical guidelines only recommend CTCA as first choice diagnostic modality in a limited number of specified symptomatic patients. Further lowering of radiation dose and improvement of the diagnostic performance of CTCA will probably expand the number of appropriate indications for CTCA. This might even include screening of high risk individuals when supported by extended research in the future.

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