Wednesday, May 25, 2011

UPDATE ON CCTA ( Coronary Computerised Tomography Angiogram )

This issue of CT angio for screening people for coronary artery disease has been debated for many, many years now. I remember when Dr Beh ( Bangsar Heart Scan ) first bought the EBCT scan ( the earliest single electronic beam scan ) it raised a hue and cry from the cardiac community. Actually, Dr Beh got the idea in the 90's from a visit that the Ministry of Health did to Australia, at that time,. I was told in confidence that the DG of Health then, was very impressed that one can visualise your coronary artery ( virtual angiogram ), without invading the body. When Dr Beh heard the idea, he negotiated with a company called Imatron then, to secure a sole rights to 5 machines, hoping to put up machines all over the country and make plenty of money. Well when his machine came up, the President of the National Heart Association Malaysia at that time, this was in the 90's, wrote a letter to the papers saying that there is no basis for such scans. From then on ( ask Dr Beh over tea, if you care ), the controversy raged on. Later on the 16 slice MSCT ( multi-slice CT scan ) came, and then the 64 slice MSCT. As God would have it, the same president, who wrote to tell the public that there was no good medical evidence for the CCTA, now invest in a 64 slice MSCT machine in town.
And the controversy rages on.
In the May 23rd issue of Arch of Int Medicine, there is an article by Dr John McEvoy of John Hopkins, Baltimore, studying the usefulness of CCTA in assymptomatic, low risk individuals.
The paper is entitled, "Impact of coronary computed tomographic angiography results on patient and physician behavior in a low risk population". They studied 2,000 assymptomatic subjects in the low and intermediate coronary risk group, and followed them up for 18 months. We cannot call them patients as they are not sick. They are like the people walking around the shopping complexes, and bus terminals. The kind, that may be tempted to do a CCTA just for the fun of it, because it is paid by insurance.
Well, what Dr McEvoy found out ( and the study was carried out in South Korea ), was that after 18 months, those with positive CCTA, only one had an event, and that non-fatal too. He concluded that "Weighing the totality of the evidence, we felt that, given the radiation dose, given the contrast, and given the increase in revascularizations and stress tests incurring extra costs, [CCTA screening] seems to be a strategy that is not optimal in patients without symptoms at low to intermediate risk for heart disease,"
In John Hopkins, USA, they use the CCTA in the Emergency department to exclude CAD, not to diagnose it.
Anyway, I am told that there are now 500 slice CCTA scans ( Toshiba ) available. This will be able to scan the whole heart in one heart beat, thereby limiting radiation and the need to beta-block the heart. It is also better for patients with atrial Fibrillation, who need to be scanned. This scan is not yet available in Malaysia. In Malaysia, we have various kinds of scans that uses the helical slice principle and some ( to increase their scan rate ) uses the dual source principle, saying that they are 64 slice with 32 anodes. It is not quite the same.
Anyway, the long and short is, if you are well, and wishes a cardiac check-up, good old cheap stress ECG, may still be the best, all things considered. Know your risk profile. Nice enticing, seductive pictures, does not mean that what you see if what you have.
I am sure that more will be known in the future. After twenty years, we are where we were before.

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