Computerized tomography, also known as CT scan, is a diagnostic modality capable of taking images of blood vessels, bones, internal organs and structures.
Yale Medicine cardiac imagers are specially trained to interpret cardiac CT scans to help diagnose a range of cardiovascular conditions such as coronary artery disease. It's a life-threatening condition caused by a buildup of fat, cholesterol, calcium and other substances in the arteries, which supply blood to the heart.
"At Yale Medicine, we are committed to providing the highest-quality equipment and the highest quality of care," says Hamid Mojibian, MD, director of cardiac CT/MRI Imaging at Yale Medicine's Department of Radiology & Biomedical Imaging. He and a team of radiologists and cardiologists perform many cardiovascular magnetic resonance imaging (MRI) and CT studies, including scans for diagnosis of coronary artery disease.
What types of people may be helped by having a CT scan for coronary artery disease?
A CT can view internal chest structures like bones, lungs and pulmonary arteries. Additionally, it is ideal to help identify whether a patient’s chest pain is a signal of a coronary event or the result of another affliction that can be even more dangerous than coronary artery disease.
This makes CT especially well-suited for those with a low to medium risk for coronary artery disease or patients with atypical symptoms.
“There are many ways to evaluate patients with suspected coronary artery disease,” Dr. Mojibian says. “A CT scan is one of the least invasive, and we typically perform it on younger patients who may be experiencing some chest pain but with only a few known risk factors for coronary artery disease."
Dr. Mojibian says CT is probably the only imaging method to reliably exclude coronary artery disease when other imaging modalities are either invasive, cannot detect early coronary artery disease or don’t have the capability of characterizing an atherosclerotic lesion.
Patients whose profile suggests a greater likelihood of having an acute coronary artery event, those experiencing chest pain with elevated enzymes would typically be sent for an angiogram. It involves a higher dose of radiation and the invasive use of a catheter, but can be diagnostic and treat the condition in a very fast fashion.
How does CT for coronary artery disease work?
The CT scanner sends X-rays through the patient’s body, which are captured by electronic X-ray detectors in the scanner. The detectors process the data from the X-rays to create cross-sectional images of the body, which are reassembled into detailed, multidimensional images of the body.
“To get the clearest possible pictures, Yale Medicine synchronizes image acquisition through the CT scanner with an electrocardiogram, both are being performed simultaneously,” Dr. Mojibian says.
He adds, "By following the EKG, we know when the patient’s heart is most still, which is the opportune moment to take images with the CT scanner. We can also, if it’s appropriate, get images of the heart going through an entire cardiac cycle, so we have a better understanding of how it’s functioning.”
What can a person undergoing the procedure expect?
Most CT scans are painless procedures that take about 10 minutes. The patient’s heart rate is checked first to make sure it’s ideally less than 65 beats per minute. Anything above 65 beats per minute will make it difficult for the CT to capture images.
If the patient’s heart rate is too high, a beta blocker might be administered to slow it down. Once the patient’s heart rate is beating at 65 beats per minute or less, nitroglycerin is given beneath the tongue, which helps to dilate the arteries. Images are acquired during injection of intravenous contrast.
During image acquisition, the patient’s body will be moved inside the scanner. The head and neck usually remain outside of the scanner.
All studies are supervised by a clinician, and a radiologist and cardiologist will interpret the results, most likely on the same day. Next, findings are entered into the patient’s electronic medical records, so the physician can review them.
How is Yale Medicine’s approach to CT imaging for coronary artery disease unique?
“We’ve always ensured that we have the highest-quality equipment at Yale Medicine,” Dr. Mojibian says. “We have a ‘dual source’ scanner—the most advanced on the market. This new scanner can get clear imaging no matter what a patient’s heart rate is, so waiting for that crucial drop to 65 or fewer beats per minute is not necessary with this scanner."
In addition to having the highest-quality equipment, Yale Medicine is committed to providing the highest quality of care. Two specialists, a cardiologist and a radiologist, examine and interpret every scanned image to ensure an accurate diagnosis.
“When a cardiologist refers a patient for a CT scan for coronary artery, steps are taken to ensure that the scan is the most appropriate test for that patient," Dr. Mojibian says.
For example, he describes a patient who had been referred for a CT scan due to some problems with kidney function. “When something like that arises, we consult with the referring physician,” he says. “In this case because people with impaired kidney function are at greater risk of kidney toxicity from the use of contrast dye, a CT scan was not appropriate."