Why the latest Heart Scans are popular..but not foolproof

With rapidly-advancing medical technology and ready sources of info from the Internet, more and more people are over-eager to submit to CT angiograms(CTA),  also known as multi-slice CT of the heart(MSCT). The popular perception is that such scans will be able to diagnose heart disease and help to prevent heart attacks.

The popularity of CTA is largely due to the fact they are non-invasive and the machines are located in non-hospital settings like shopping-malls and office complexes. All a patient needs to do is to lie down, take and hold a deep breath, have a dye injected into a vein in the arm and the whole procedure can be over in a matter of less than 15 minutes. Soon, the patient is presented with colour copies of  very graphic 3-D images of his heart, showing where there are blockages in the coronary arteries, if present.

To a certain extent, commercialism have crept in to boost the popularity of these scans. Many of these machines are physician-owned  and consequently there may be over-utilisation in order to recoup the USD 1 million cost as quickly as possible.(It will take something like 3000 scans to pay off the machine cost)

CTA of the HeartThe CTA shows details of blockages of the heart arteries in fine detail.(courtesy of Dr Harvey Hecht)

What is not generally known is that CTAs use radiation to capture the images. A single heart-scan can expose you to as much as 21 millisieverts of radiation —  equal to about 1,050 conventional chest X-rays!

Apart from this, the accuracy of these scans are both machine-dependent as well as operator-dependent. There is a learning curve for any new technology and experience is still being acquired to obtain the best interpretation.

Perhaps the most important factor that needs to be appreciated is that the chances of getting a total blockage (and a heart attack) is not always dependent on the severity of the blockage. This has been proven often as the most minor of blockages can lead to a total blockage in a matter of seconds, following a plaque rupture. So, even a CTA with minor blockages can be as disastrous as one with several severe blockages.

The dilemma facing healthcare providers recently received good coverage from the New York Times.

Even doctors are debating as to who should have one done. Therefore, it is important to appreciate that, while new technology will bring benefits, it must not be used indiscrimately.

It can then become a tool of questionable value that is used by impatient patients.

6 responses

  1. Interesting…are you saying one should beware of CT angiograms as they are rather harmful due to radiation?

  2. Hi Doc,

    I find this approach to the ‘wonders’ of technology refreshing. I have a healthy doubt of doktors and dukuns and am appalled that many doktors nowadays are just drug-pushers. When I went to my first school (Sekolah Melayu) it was near the TB ward of our GH. Sometimes when I strayed beyond my remit and travelled to the confines of the hospital, I’d see the patients being pushed out to enjoy the morning sun. Now we read that Vitamin D is the source of life and that everyone should expose themselves more to the sun, better than swallowing Vitamin D which can lead to toxicity. Er, ahem, what about all that mercury in the vaccines? Power to your elbow doc (or whatever you use to diagnose patients). Good blog.

  3. Yes, there was a time when we would make patients get a bit of fresh air and sunshine, but both are a rarity nowadays with the environmental pollution that is omnipresent.
    Vitamin D..that sounds a good entry for the next blog entry 🙂 Thanks for your comments

  4. Victor,
    As in any medical procedure, one has to weigh the risks and benefits.
    You would go for it if the benefits outweigh the risks.
    One of the main intentions of my blog entry is to empower the consumer to be aware of the risks before undertaking any procedure.

  5. Doc,
    Looks like what you’re saying is right. My doc just showed me this link and it says that this CT heart test should NOT be used as a routine screening test.


  6. Thanks for the info. Despite the shortcomings of the MSCT, I’d much rather have it done rather than the more invasive but slightly riskier coronary angiogram which would reveal the same amount of information as the MSCT itself. Similar with the MSCT, the angio too cannot truly determine which ‘minor blockages’ are likely to rupture & cause a total blockage in the matter of seconds. The fact is that a non-invasive alternative is now available for patients with lower IHD risks to find out whether any blockages are present. With regards to radiation, the angio itself involves exposing the patient to a large amount of radiation as well although it is correct that the amount of radiation is greater in the MSCT (quoted to be twice the amount of received during conventional angio). Keep up the good work & keep the info coming, doc.

    Doctor2008 replies: To set the record straight,most cardiologists would hesitate to say that the MSCT heart-scan would reveal the same info as an angiogram, particularly when there are heavy calcium deposits, which gives rise to a ‘flaring effect’ which prevents an accurate picture of the extent of the blockage.
    That is why the angiogram still remains the ‘gold standard’ for defining blockages.
    The heartscan has its uses but nowhere is it recommended as a medical check-up for heart disease in asymptomatic, otherwise well individuals who have a low risk of heart disease. Even so, there are many private centres offering this scan as part of an executive screening package.this is not justified, in my opinion.
    There is an excellent article on who needs heartscans at http://www.mayoclinic.com/health/heart-disease/HB00015.
    Thanks for your contribution. 🙂

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