Coronary Computed Tomographic Angiography (Coronary CTA) is a new, noninvasive imaging test that is specifically designed for the coronary arteries.
Coronary CTA is a cardiac gated volumetric contrast-enhanced CT angiogram yielding two dimensional and three dimensional pictures of the coronary arteries with the heart motion “frozen” in diastole. Whereas conventional (EKG, serum cardiac enzymes, and stress perfusion) noninvasive procedures detect only significant flow-limiting stenoses, coronary CTA is a CT scan that provides anatomic images of not only the vessel lumen, but more importantly the vessel wall. The wall of the artery is the affected end-organ in atherosclerosis. Lumen narrowing (stenosis) is the end result of the disease but the majority of fatal and debilitating MIs are due to non-flow limiting stenoses.
Coronary CTA is the only noninvasive or invasive test that can detect, quantify, and characterize atherosclerotic plaque from its early stages of fatty streak, to lipid core, to fibrosis, and eventually to calcification. Even the gold standard of invasive catheter angiography only measures the vessel lumen and gives limited information about the nature of the actual disease process occurring in the vessel wall.
Coronary CTA can identify atherosclerotic plaque at risk of rupture, including the potential to cause myocardial infarction in the prestenotic stage that would not be detected by EKG or stress perfusion.
Large studies comparing coronary CTA to the gold standard of coronary catheterization have shown excellent correlation with sensitivities greater than 90%, and negative predictive values of as high as 99%. With proper patient selection, coronary CTA is an excellent alternative to catheterization and stress test. Coronary CTA actually yields more information about early atherosclerosis than conventional invasive and noninvasive means.
The desired heart rate is less than 70 BPM with a stable cardiac rhythm. Patients with heart rates consistently higher than 70 BPM, despite beta blocker therapy or irregular cardiac rhythm, would be considered poor candidates for this test. Excessive coronary calcification limits the ability to characterize the vessel wall & vessel lumen. Patients with large body habitus would be considered less than ideal candidates given reduced signal-to-noise ratio. Patients w/ acute coronary syndrome should be treated by conventional emergent means and would not be considered candidates for coronary CTA at this time.
The Radiologist at Advanced Imaging will provide prescriptions for 100 mg of oral Metoprolol to be taken one hour prior to the examination. Oral anxiolytics are prescribed by the patient’s physician for the procedure if indicated. Anxiety can cause an elevated or irregular heart rhythm.