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Safety Risk of Multislice CT Angiogram Compared to Cardiac Catheterization

May 9, 2006 -- Two articles in the recent Journal of the American College of Cardiology, published online on April 17, address the debate of how non-invasive MultiSlice Computed Tomography (MSCT) imaging compares to standard angiography (cardiac catheterization) on the issue of safety.

One of the few drawbacks of MSCT has been the higher dose of radiation involved. This is discussed in article 1 below in a study done at the Bristol Heart Institute in the U.K., showing that the radiation dose "was significantly higher" for MSCT. The concern, of course, is that higher radiation doses have been shown to increase the incidence of cancer later on. This finding has been questioned by at least one researcher who commented that the amount of radiation used in the U.K. study was more than usual, and that newer methods, such as ECG gating, have reduced that amount by almost half. (ECG gating synchronizes the X-ray emitter to the patient's heartbeat, so that the only one part of the heartbeat cycle gets the full radiation dose).

However, radiation dose is not the whole safety story. Article 2, "Risk Has Its Reward", was written by researchers at New York's famed Memorial Sloan Kettering Cancer Center, and their interpretation is that MSCT is safer when taking into account the "overall risk" of both procedures. The risk of radiation-related cancer fatality over a partient's lifetime for standard angiography is 2 in 10,000; for MSCT it's 7 in 10,000 (again, this higher figure is disputed by many imaging specialists).

But the non-radiation risk of mortality in angiography is an additional 11 in 10,000, so (2 + 11 = 13) the actual "overall risk" for standard angiography is 13 in 10,000 -- almost double that of MSCT. If one uses the lower estimates of radiation for MSCT, then the safety factor is two, three or more in favor of CT angiography. Additionally this study did not take into account the various major and minor complications experienced with the more invasive cardiac catheterization angiography (around 2-3%) that can occur (access site complications, nerve trauma, hematoma, pseudoaneurysm, etc.).

The study concludes:

"For an equivalent clinical diagnostic efficacy of MSCT angiography and CCA [Conventional Coronary Angiography] (2533), MSCT angiography emerges as the safer of these two alternatives, despite its higher radiation dose."