Patients at low risk of heart disease are having their heart examined between beats, utilising new cardiac computed tomography (CT) scanning as an alternative to conventional angiogram scans. The CT is used to assess the risk of coronary heart disease in patients presenting with niggling chest pain, where an echocardiogram (ECG) and blood results are normal.
The cardiac CT scan measures the extent of calcification of the heart valves and vessels, as well as examining the vessels for narrowing or "stenosis". It takes a snapshot in one pass or revolution, at the point between beats.
Epworth Radiologist, Dr Greg Compton, says this new way of looking at the heart helps doctors rule in or out coronary heart disease when a patient is experiencing chest pain.
“We are also seeing it used for pre-operative assessment of patients with known coronary disease, or to look for congenital heart issues that are sometimes missed using an echocardiogram,” Greg says.
By taking the image between heartbeats, doctors can prevent the beating heart interfering with the image quality. It also decreases the exposure to radiation.
While only taking a few moments, involves taking a beta blocker the night before to help make the heart rate more predictable during the scan.
“We want to get the heart rate down to less than 65 beats per minute (BPM). Where patients have a resting heart rate of less than 65 BPM, we still administer the beta blocker to ensure we can predict the best time to take the image. In effect we want to control both the rate and the rhythm,” he says.
On the day of the procedure, the patient needs to fast for a period of 4–6 hours before the scan. Once at the hospital, an intravenous drip will be placed in the hand or forearm, into which the contrast dye is injected. The contrast dye is needed to view the inside of the vessels.
With all this preparation, the scan is ready to be taken. “Once we have the patient in the correct position and the machine is going, it only takes a moment for the scan itself,” Greg says. After the scan, the results are analysed the same day.
“We are looking at the calcification to see whether it is more, less or average when compared with age and sex-matched data.
“With the contrast dye, we are looking at the blood vessels in a similar way to an angiogram, but a lot less invasively. We classify the patient’s risk as severe, moderate, mild or minimal. Those in the severe or moderate categories may progress to the catheter lab for an angiogram and potential stenting, whereas those in the mild or minimal categories can be managed conservatively,” Greg says.
The method is only considered where patients are at low risk of coronary heart disease, such as those patients who are under 55 years of age and non-smokers.
Greg says that cardiac CT is becoming increasingly popular as more GPs and cardiologists become aware of the benefits of the cardiac CT scans.
Epworth Medical Imaging offers 7-day service with radiologists, nurses and specialist imaging staff appointed to streamline patient care. Go to www.epworthmedicalimaging.com.au for more information.