HOSPITAL'S HEART SCAN IS PARTICULARLY VALUABLE FOR SOME PATIENTS
The report by Mary Ann Benitez (South China Morning Post, December 5) on Matilda Hospital's Electron Beam Tomography (EBT) heart scan has created negative views in the public eye.
As a doctor with no personal relationship with Matilda Hospital or with doctors practising there, I feel readers may have been misled about the value and use of the EBT scan.
Your report stated that one 50-year-old company executive underwent the scan and was diagnosed with 'left main artery' disease, but subsequently underwent an invasive angiogram which revealed everything was normal.
It is important to understand that the EBT quantifies the amount of calcium that is in the coronary artery and is not aimed at providing information about the degree of narrowing of the coronary arteries. The greater the calcium score, the greater the 'atheroma burden' for that vessel.
A coronary angiogram, on the other hand, provides precise information about patency (that is, unobstructed) of coronary arteries.
In patients with cardiac chest pain, a coronary angiogram is useful to determine how much narrowing there is and whether angioplasty or bypass surgery is indicated. On the other hand, an EBT scan is useful in individuals with high risk (such as diabetic patients) who have no symptoms, as it may serve as a guide to aggressiveness of therapy.
An EBT scan may show a very high calcium score and angiography may show complete patency in that very segment of artery. Yet a completely patent coronary artery does not mean that the vessel is normal or healthy. This is because the vessel may not be able to enlarge to allow greater blood flow under conditions which increase the heart muscle demand for oxygen (such as exercise). Therefore, an EBT scan provides information totally different from that of an angiogram and is particularly valuable for patients who have risk factors for coronary heart disease and yet have no symptoms (chest pain or angina). The presence of a moderate to high calcium score indicates the need for more aggressive control of coronary risk factors (such as diabetes and high cholesterol). The EBT scan result may even make the difference in patients who have difficulties in giving up smoking as these people can clearly visualise that their coronary vessels are diseased (and of course these vessels can still be completely patent if they chose to do an angiogram).
At present, the EBT scans are widely used in the US and their use is increasing in the UK mainly in medical research. Indeed, Hong Kong is indebted to Matilda Hospital which has set up the first EBT scan for at-risk people.
As a diabetologist, I treat many diabetic patients who have no cardiac symptoms but have multiple risk factors. Some of these patients warrant an EBT scan as the result may help to determine the aggressiveness of therapy.
There is a clear role for the use of an EBT scan in the management of high-risk asymptomatic individuals.
The non-invasive nature of the EBT scan makes it particularly attractive.
Dr NORMAN CHAN
Chief Medical Officer
Qualigenics
Centre for Diabetes and
Endocrine Disorders
Prince of Wales Hospital Campus
Mary Ann Benitez replies: In a story on November 26, not referred to by Dr Chan, we reported that: 'The accuracy of a hi-tech heart scan at the exclusive Matilda Hospital is being questioned by the Hong Kong College of Cardiology after several patients were told they had heart disease but were subsequently found to be healthy.
'Doctors not associated with Matilda estimate dozens might have been sent into a panic after receiving reports of high calcium scores and heart disease.'
The company executive also underwent a further test at Matilda, using the same machine, before he was diagnosed with a 'left main artery' problem.
He spent $18,000 on the tests at Matilda and about a further $20,000 for tests at Adventist Hospital, to make sure that he was disease-free.
