Taking pictures of the heart is an important part of diagnosing coronary artery disease (CAD) and predicting heart attacks. CTA (computed tomographic angiography) is a relatively new technology that visualizes heart muscle and coronary arteries.
CTA technology is also called high resolution CT, multi-slice CT, and 64 slice CT.
Is CTA Accurate?
Few studies have been done comparing CTA results to invasive coronary angiography, the gold standard, in the same patient. It appears that CTA is accurate about 90% of the time.
Does CTA Predict Heart Attacks?
The more abnormal blood vessels found on CTA, the more likely you are to have a heart attack. In the future, CTA may be combined with nuclear imaging for even more accurate diagnosis and prognosis. These two modalities provide images of both the coronary arteries and blood flow to the heart muscle.
Is CTA Safe?
CTA uses contrast material (dye) injected through an IV (intravenous line). IV contrast can cause allergic reactions and kidney damage which can lead to dialysis. If you have a known allergy to contrast dye or chronic kidney problems, carefully discuss your specific risks with your doctor prior to obtaining a CTA.
The CTA protocol often requires a slow heart rate. The medication used to slow the heart can be problematic in those with asthma or slow heart rates at baseline.
Imaging the heart with CTA includes significant radiation exposure. It is not clear whether there is an increased risk of cancer from this radiation.
Finally, an abnormal CTA scan usually leads to further testing with invasive coronary angiography; a procedure that also uses IV contrast dye and radiation. The risk is thus doubled in those with an abnormal CTA.
Who Should Have a CTA?
It’s not clear who can benefit most from a CTA. One study showed that those who present to an emergency room with symptoms of a heart attack can be evaluated more quickly if a CTA is done.
CTA provides significant information on all the structures in the chest, not just the heart. The lungs, blood vessels, and heart muscle are all imaged. Lung abnormalities as well as vascular issues such as aneurysms can be diagnosed. A unique benefit of CTA is its ability to detect if coronary arteries take an abnormal path through the heart muscle (congenital anomalies).
Discuss with your doctor the risk of IV contrast dye and radiation involved in the CTA procedure. As noted above, an abnormal CTA often leads to invasive angiography and even more dye and radiation. Your doctor may recommend you proceed directly to the invasive procedure despite the slightly higher risk of using catheters to access the heart.
As CTA technology evolves, the amount of IV contrast dye and radiation will likely decrease. CTA can potentially become the ideal noninvasive test for detecting CAD.
Source:
Pundziute G, Schuif JD, Jukema JW, et al. Prognostic value of multislice computed tomography coronary angiography in patients with known or suspected coronary artery disease. J Am Coll Cardiol 2007;49:2070-1.