Dr Chow Hui Jeremy
It is hardly an overstatement that many people consider coronary artery disease (CAD) one of the major threats to global health. The condition – a narrowing of the arteries due to fatty plaque that may cause a heart attack – was responsible for 7.4 million deaths in 2012 alone, according to the Worldwide Health Organization.
CAD is a chronic ailment that develops over several years or even decades, so early diagnosis is crucial to stop its progression and avoid heart failure.
If you think you are at risk of heart disease, arrange for a heart screening with a specialist.
"Coronary angiography is the gold standard for diagnosing coronary artery disease because it is a diagnostic tool with a therapeutic option," says Dr Jeremy Chow, cardiologist at Gleneagles Hospital.
According to Dr Chow, most physicians now perform this procedure through the radial artery – a small artery in the wrist – where a small catheter, typically 2mm in diameter, is placed in the artery and fed along the artery path to the heart. "Once it is inside the heart, we are able to locate the 2 main arteries – the left and right coronary arteries – and engage them using the catheter and inject dye," he says.
X-ray images are subsequently taken to monitor how the dye moves through the artery and locate any blockage in blood flow.
Dr Chow explains that when a blockage is found, doctors can introduce other equipment into the artery, such as balloons, stents or wires, to clear the obstruction and prevent a future cardiac arrest.
A coronary computed tomography angiogram (CCTA) is a less invasive test to diagnose CAD because it only involves an intravenous injection of a contrast dye in the vein and can usually be done in around one hour.
During a CCTA, the contrast dye is followed through a CT scan to search for any blockage in the arteries without the need for a catheter.
Dr Chow says that the accuracy rate of a CCTA is 99%. Therefore, when the machine does not detect any blockages, there is no need to proceed with further evaluation.
However, a CCTA is less reliable when it comes to detecting serious obstruction, with its accuracy rate ranging from 70 – 80%, says Dr Chow. This means that someone who starts off with a CCTA may end up needing a coronary angiography as well to obtain a clearer picture of the blood vessels.
In addition, a CCTA needs a slow resting heart rate – normally between 60 and 75 beats per minute – in order to acquire clear images.
"If your heart rate is very fast, you may end up having to do the CT scan a couple of times, which means your amount of exposure to radiation may be a little bit higher," says Dr Chow. "A coronary angiography doesn't have that limitation, however, so you can do it with any heart rate."
Individuals with a family history of heart disease or at least 2 risk factors for artery blockages, such as smoking, high cholesterol levels, diabetes, or hypertension, are encouraged to go for screening.
Patients in the at-risk group are required to undergo a stress test first, says Dr Chow. This involves an electrocardiography machine that monitors their heart function while they exercise on a treadmill. If the results from the stress test are abnormal, patients may need a follow-up coronary angiography or CCTA.
To arrange for a heart screening, make an appointment with a specialist.