CT Coronary Angiography - A new tool for the diagnosis of heart disease


Multi slice CT Coronary Angiography with 64-slice technology is emerging as the most reliable non-invasive modality for evaluation of heart disease. Impressive image quality and non-invasive nature of Multi Slice Computed Tomography(MSCT) angiography makes it a powerful tool in evaluation of heart disease. CT Angiography (CTA) is an examination that uses x-rays to visualize blood flow in coronary arteries which supply blood to the heart. CT combines the use of x-rays with computerized analysis of the images. Beams of x-rays are passed from a rotating device through the heart from several different angles to create cross-sectional images, which then are assembled by computer into a three-dimensional picture of the heart. When a cardiologist needs to diagnose disease in heart arteries( coronary artery disease),i.e If EKG's, stress tests or other indicators have revealed a potential cardiac problem, the next step is for the cardiologist to get a close-up look at the arteries in the heart, to see where there might be blockages.In this case, cardiac cathetrization with conventional coronary angiography is the best tool. during which a physician inserts a catheter into the circulatory system, advances it to the heart and injects dye into the coronary arteries.Because the X-ray is a "shadow" image that is two-dimensional, the cardiologist has to interpret a number of different "camera angles" that were shot to determine the presence and shape of any obstructions to the blood flow. But a much better diagnostic option would be a detailed 3D virtual model of the patient's heart -- so that the cardiologist could rotate, zoom and move through the heart's anatomy at any angle at will, as if it were a video game. And without impacting on the patient! MSCT angiogram overcomes these limitations In less than 30 minutes, without the invasiveness of a cardiac catheterization, a patient can have an MSCT done to determine if there are any arterial blockages that require an intervention, such as an angioplasty or stent. The only immediate impact on the patient is an IV injection with iodine-containing contrast and possibly a beta-blocker to slow the heart beat (the equivalent of saying "cheese" and holding still for the photographer).

Speed and sensitivity of 64 slice CT, now gives physicians a new way to view the heart and surrounding structures. Coronary CT angiography captures thousands of images of a beating heart in mere seconds. The 64 slice CT captures images of anatomy as thin as a credit card. 3-dimensional reconstructed images are then formatted, allowing physicians and their patients to easily review and understand findings of the CT scan. Patients undergo CT angiography without being admitted to a hospital. The ability of this technology to non-invasively image the coronary artery lumen and wall constitutes an attractive addition to currently available diagnostic tools such as nuclear perfusion imaging or conventional selective coronary angiography, for patients with known or suspected CAD.

MSCT provides a less invasive and less expensive method of ruling out the need for additional intervention if no blockages are detected. If significant blockages are found, then the patient is referred to a cardiac catheterization with a probable angioplasty or stent.An interesting feature of CT Angigraphy scans comes into play if some disease is found . Physicians have reported that when patients see such a clear and understandable picture of their heart, they are much more motivated to make lifestyle and other changes to lower their risk factors.Drug therapy is very useful in these patients to help prevent progression of blockages and heart attacks.As MultiSlice CT becomes more widespread, it is likely that several of heart related tests will become less and less used.

A growing number of studies have suggested that 64 slice coronary CT angiography is highly accurate for the exclusion of significant coronary artery stenosis with negative predictive values of 98%-100% in comparison with invasive selective coronary angiography. This means that when the study is reported to be normal, it will be normal. This makes it a more accurate test than stress-testing(TMT), stress-echocardiography, stress-thallium and stress-perfusion MRI. More importantly, the heart does not have to be stressed to get this information. Early stages of coronary atherosclerosis can be detected before the development of coronary arterial narrowing. Methods of characterizing the type of plaque in the arteries has been refined, so that "vulnerable" plaques that are more likely to rupture can be pinpointed for treatment, reducing the risk of heart attack. Right now, MSCT provides a significant "next step" to patients whose stress tests have proven inconclusive, and who may have a good chance of being "screened out" for coronary artery disease.


Which group of patients require it?