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“Noninvasive CT scans cannot replace imaging of coronary artery blockages by conventional invasive angiography”, according to the New England Journal of Medicine.

The CT imaging techniques have developed very fast and during recent years the use of CT to image coronary arteries has been quickly growing. But according to a new study published in the New England Journal of Medicine -“noninvasive CT scans cannot replace imaging of coronary artery blockages by conventional invasive angiography”

Although it was initially hoped that this noninvasive test could even replace invasive coronary angiography, it has been clear of years that this is not the case. Accordingly ESC imaging, experts have recommended CT angiography to be at the best in excluding coronary artery disease in the patients with low to moderate pre-test possibility of disease. The strength of CT angiography in the previous studies was the very high negative predictive value i.e. when the result of test is negative the important coronary artery disease is very unlikely.

The study conducted by JM Miller and colleagues is the first multicentre trial for 64-slice CT angiography and demonstrated good accuracy but the negative predictive value was somewhat lower (83%). This raises questions whether the technique is indeed very precise in excluding coronary artery stenoses when applied in clinical routine and in multiple sites.

Another issue discussed was the radiation risks of the CT scans. It is clear that all necessary actions are needed to minimize the risks of imaging, including radiation risks. The radiation doses by CT were 2-3 fold higher than in invasive angiography, but still in moderate level in the discussed study. However, with the current generation of CT scanners, which were not widely available at the time the study was started, the radiation dose is ranging from 3 to 7 mSv, which is actually less than with invasive angiography. Newer techniques are looking at lowering the radiation dose even further.

While CT can diagnose coronary stenosis, functional ischemia testing is needed to assess whether coronary stenoses are hemodynamically significant. This can be done by cardiac nuclear imaging, stress echocardiography, magnetic resonance imaging or invasive flow measurements. Using CT, now also noninvasive imaging of coronary anatomy is possible and it is very likely that this information will be combined with functional imaging findings making finally comprehensive noninvasive evaluation possible.

Source: European Society of Cardiology Press Office.