Angry Doctor

Tuesday, July 17, 2007

A little learning...

The title of this letter to the ST Forum today caught angry doc's attention the moment he opened the webpage:

Check your heart condition - go for a CT scan

THE Sunday Times on July 15 reported yet another case in which a healthy soldier collapsed and died of a heart attack during a taekwondo exercise.

I am saddened by all these good men and women, some relatively young, who left their loved ones all of a sudden without a chance to even say goodbye.

We have read enough cases to know this silent killer does not respect age, gender or fitness level. Some of these individuals have even gone through very recent health checks like treadmill stress and blood tests and they were certified a clean bill of health by their doctors. Some don't even have any complaints of any chest pains or tightness whatsoever before the heart attack.

Here is my personal view of this matter from a layman's perspective which, I hope, would trigger readers to think carefully of what they know, rightly or wrongly, about this deadly killer disease.

Here are some common myths that I often hear people bringing up in the course of discussing this topic on heart attack:

'My cholesterol level and treadmill stress test results are OK - my heart condition therefore should be OK.'

There is no direct correlation of cholesterol readings to plaque forming and clotting properties in our blood. Plaque forming in the inner walls of our blood vessels may rupture over time and cause blood clots to form at the site and if the clot is large enough to block the flow of oxygen-rich blood to the heart muscles, the heart muscles may die and be replaced by scarred tissues. Other non-clotting related causes like spasms causing blood vessel constriction leading to a heart attack is not discussed here.

The exercise stress test - also called a stress test, exercise electrocardiogram, treadmill test, graded exercise test or stress ECG - is a test used to provide information about how the heart responds to exertion. It usually involves walking on a treadmill or pedalling a stationary bike at increasing levels of difficulty, while your electrocardiogram, heart rate and blood pressure are monitored.

This test is able to detect a heart condition 15-75 per cent of the time, depending on many factors and may not be able to accurately diagnose a problem below 50 per cent blockage in your arteries. So that may explain why some people still suffer from a heart attack soon after passing a treadmill stress test.

I learnt of a local marathon runner having a mild heart attack and yet passed the treadmill stress test three times via three different cardiologists.

The treadmill stress test may not be stressful enough for some fitness fanatics to show up any signs of the heart under stress during standard physical exertion tests. I was told that eventually this person went through an angiogram and finally found two out of three arteries with more than 90 per cent blockage. He underwent a heart bypass and lives to tell the story.

Moral of the story is that if you are super fit, you may not have a standard stress test to tell you that you may have a heart condition.

Most doctors usually will not recommend further examination if one passes the treadmill stress test. If abnormal stress signs of the heart are found, the doctor would normally recommend an angiogram to be performed.

Angiogram is a gold standard test used for some time already to determine whether one has a blockage or not. Angiogram is an invasive test where a thin catheter with a scope is threaded into your body to look at the problematic region and is able to provide only a two-dimensional view of the state of blockage in your blood vessel. It has a 10 per cent risk where it could puncture your blood vein or artery along the way to the site and some people actually died from it.

'I am physically fit and health conscious - I run 5 miles daily and exercise regularly.'

I strongly believe that if one who is very active in sports and yet does not know whether one has plaque forming in his/her blood vessels (some as microscopic as less than 1 mm in cross sectional diameter), one has a higher propensity of succumbing to a heart failure compared with one who is less active.

One may be able to run five miles a day effortlessly when one is 18 years old but when one is older... 35 or 50 years old, more effort may be required as fitness level degrades over time.

As you age and when you are not as fit or are unwell, your heart actually pumps faster with the same degree of physical exertion. With the plaque building up and the tendency of the plaque rupturing getting higher each day, the risk of a heart attack increases over time. I believe the same can be said in the case of a stroke affecting the blood flow to the brain through the left and right carotid arteries.

If you are active into sports or into strenuous exercises and especially if you have a family history of heart attacks or stroke, stop what you are doing immediately and ask yourself: 'Do I have plaques forming in my blood vessels today? How do I find out if a treadmill test is not accurate enough and angiogram is risky?'

Fortunately, there is a non-invasive imaging technology today called the CT scan. It is able to radioactively scan your heart with a three-dimensional computerised view of your heart and surrounding veins and arteries and also able to perform a cross-sectional analysis to show levels of calcium blockage in any part of the veins and arteries. The technology is getting better each day in terms of imaging resolution and lower radiation dosage.

Some people are concerned that the high level of radiation may shorten one's life - effective radiation dose of 2mSv which is about the same as an average person receiving from background radiation in eight months.

But think again, isn't it better to know beforehand that you do not have blocked veins and arteries that may potentially cause you to suffer a heart attack and after which, if you survive, may require you to undergo all kinds of invasive tests and surgeries? The benefit of accurate diagnosis far outweighs the risk.

My wise doctor told me it is a no-brainer for people of a certain age (>40) and those with a family history of heart attacks or strokes not to use this technology that is available today. It costs about $1,100 per scan and getting cheaper, no fasting required, requires one injection of contrast and 30 minutes of your time to go through this relatively simple examination. The doctor will go through the results and you will also be given a computer disk with your heart images to take home.

I personally went though a comprehensive insurance health screening recently which included a treadmill stress test and immediately after the test, which I passed, I paid for an additional CT heart scan and an ultra-sound test on my carotid arteries. I passed all the tests.

For those who have been spending $100-$300 on a treadmill stress test, my advice is to save the money to do a CT heart scan instead. You may want to know that you can also use your CPF Medisave savings to subsidise the CT heart scan up to $1,100 limit.

Do yourself and your loved ones a favour, get a CT scan of your heart today. Keep fit and eat healthily... but check your heart condition first.

Quek Kwang Seng

Mr Quek put a lot of facts and figures in his letter, but the issue is really more complex that that.

A multislice CT angiography may have high sensitivity and specificity, but the positive predictive value and negative predictive value will vary according to the population being examined; and it is here that Mr Quek's line of argument unravels.

Mr Quek had begun his letter looking at 'yet another case' of a healthy person who suffered a sudden cardiac death, but he also acknowledges that the advice from his wise doctor applies to "people of a certain age (>40) and those with a family history of heart attacks or strokes".

If we screened only people with risk factors, we will not reduce the number of sudden cardiac deaths in 'healthy' people. If we screened all 'healthy' people, the cost will be enormous, in the region of a $1 billion or more given our population, while the number of deaths we stand to prevent will be small.

And that is not all.

Coronary artery disease (CAD) is a progressive disease: just because you have a clear CT angio today does not mean that you will not develop a problem later on. At the same time, persons with 'positive' scans but are otherwise asymptomatic may not benefit from intervention in the form angioplasty. The cost is therefore not $1,100 for a lifetime, but $1,100 every few years or so. Is it more effective to screen and treat risk factors for CAD with that money, or is it more cost-effective to detect the disease when it is already established? Certainly that is something we need to study.

A multislice CT angiography is good at picking up (or excluding) coronary artery calcification and plaque burden, but CAD consitutes only about 80% of sudden cardiac death cases; the other 20% of cases are attributed to (among other things) electrophysiological abnormalities, which may not be detected with a multislice CT.

There are other issues in Mr Quek letter that need to addressed, and no doubt angry doc's readers can find a few themselves. angry doc suspetcs that right now, someone from the Heart Centre or Heart Institute is drafting a reponse to the ST Forum to forestall an influx of healthy people flocking to their clinics to ask for the miracle heart scan. Doctors will need to spend a lot of time over the next few weeks explaining to patients why they do not need that special scan.

angry doc believes Mr Quek wrote his letter with his heart in the right place, but a little learning can mean a lot of work for doctors...



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