CT Coronary Angiography

An advancement in computerized tomography (CT Scan), allows cardiologists to see the coronary arteries directly without invasive procedures. In the past, a cardiac cath was the only way to see the coronary arteries directly and definitively exclude blockage. A cardiac cath requires the insertion of a catheter into the femoral artery, which is then moved up into the heart to directly visualize the coronary arteries and exclude blockage. With multislice CT technology the same arteries can be visualized without the insertion of a catheter.

With CT coronary angiography the images are obtained over a ten to twenty second period. Contrast is injected through an IV in the arm immediately before the pictures are taken. No catheter, no incision, and no arterial puncture are required.

CT scans should not be confused with MRI. MRI is magnetic resonance imaging and requires a larger tube shaped machine. MRI machines often produce a loud banging noise and are difficult for claustrophobic patients. The multisclice CT scan is opened and the problems associated with placing a patient in a confined space are not present. The multislice CT scans use x-rays which do not interfere with pacemakers like the magnetic fields created by MRI.

Multislice CT scanning is an excellent tool for patients with previous coronary artery bypass grafting. The scans can be used to definitively determine if the surgically placed grafts are still open without subjecting patients to an invasive procedure. CT coronary angiography is also extremely useful for patients with equivocal stress tests who do not want to be subjected to an invasive procedure. In the past patients with marginally abnormal stress tests have gone for cardiac caths to exclude coronary artery disease. CT coronary angiography now offers an alternative method allowing patients to avoid invasive procedures solely for diagnostic purposes. Additionally CT coronary angiography is the modality of choice for identifying coronary anomalies. A coronary anomaly is a variation in the usual anatomy of the arteries which supply the blood to the muscle in the heart. People are born with these anatomical variations, which may or may not cause a problem depending on the particular type of defect.

CT coronary angiography does have some limitations just like any imaging modality or medical procedure. If the heart rate is too fast it is difficult to image the coronary arteries with multislice CT. Patients are given beta blockers prior to the scan in order to lower the heart rate below 70 beats per minute so that better images can be obtained. CT coronary angiography also requires the patient to hold their breath for about 15 seconds and to remain absolutely still during the 15 second period the scan is done. If patients can not hold still or breathe during the scan it markedly reduces the image quality. It is also important to keep in mind that CT coronary angiography is a diagnostic procedure only. If interventional therapy such as stent placement is required then traditional invasive techniques need to be used.