Is fast CT imaging as accurate as invasive heart blockage tests?
A study spanning 8 countries, 16 hospitals, and 381 patients has concluded that a superfast computer tomography scanner is just as accurate as more invasive tests like cardiac catheterization and angiography in diagnosing coronary blockages. The study, co-authored by Johns Hopkins University School of Medicine professors Joao A.C. Lima and Richard George, and cardiologist Carlos E. Rochitte of the Heart Institute (InCor), University of São Paulo Medical School, in Brazil, compared a 320-detector CT with conventional tests like single-photon emission computed tomography (SPECT) and invasive angiography.
The 320-detector CT was used in two different types of tests labeled as CTA and CTP; the A stands for angiography and the P for perfusion, respectively. The former test consisted of scanning the vessel anatomy of the patient to see if there were blockages. In the latter a vessel-dilating, blood flow-increasing was administered to the patients to recreate the circumstances of stress tests; other than that both tests were identical and done with the same machine. The researchers were not only able to detect blockages, but also determine whether they were serious enough to decrease circulation to the heart.
Currently, patients experiencing chest pain but with no evidence of heart attack –according to an EKG or otherwise- are either tested with SPECT or referred to a cardiac catheterization lab for an angiography. SPECT is a non-invasive but inconclusive imaging stress test; as a result many people are subjected to an arterial blockage-opening procedure known as angioplasty, even though they don’t really need one. On the other hand, angiography is an invasive diagnosis test that employs special dyes and X-rays, among other things. In 30% of the cases, all angiography does is show that there are no blockages, or too few to warrant surgical intervention.
The researchers found that 91% of the instances in which the CT scan ruled out blockages, the corresponding patients wouldn’t have needed stenting, bypass, or any other type of invasive surgical procedure. In addition to avoiding invasive treatment, they could have also avoided invasive testing, given that the 320-detector CT scan had the same level of effectiveness in establishing who should be eligible for revascularization and who shouldn’t, with only one revolution around the body. An added benefit is that both CTA and CTP tests generate less radiation between the two than the 64-detector CT scanner used in angiogram and nuclear medicine stress tests.
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