April 2006, Lifestyle Magazine
My Heart Will Go On
by Tan Shee Lah
You dutifully go for your medical check-up every year? So did many of the not-old people who had sudden, fatal heart attacks. The routine medical check-up is likely to only pick up serious blockages in your heart arteries, but like cardiologist, Dr Michael Lim says, even a non-critical blockage can be potentially life threatening.
"The laymen's belief is that heart attacks only occur if the heart arteries gradually get narrower and eventually become significantly blocked. This is a common myth," warns Dr Michael Lim, Past President of the Singapore Cardiac Society, current President of the Asia Pacific Society of Cardiology and Advisory Board Member, World Heart Federation.
Not so serious, but enough to kill
"In fact, if your arteries get blocked gradually over many years, quite often, you don't get a heart attack unless you do something unusually strenuous. Most attacks occur suddenly. Don't be complacent if your treadmill test results look normal. If the results are abnormal or if you have typical chest pains, the narrowing in the heart artery is usually more than 70% of the vessel diameter."
In Singapore, every five days or so, a person in his 20s or 30s suddenly collapses and dies. Dr Lim says in most of these cases, the cause is heart disease. Yet, the victims had no history of heart disease, and their deaths came as a complete shock to family and friends who all remember them as perfectly healthy.
"This is because, two-thirds of heart attacks occur in patients with only 40-60% narrowing of their heart arteries. They will not feel chest pain, and a treadmill test may not detect any problem. very often, these people appear fit and might be joggers or cross-country runners. Their arterial narrowing is not severe enough to cause symptoms, but they are at risk of suffering a fatal heart attack.
"The routine tests used by doctors are picking up many people with more than 70% blockage, but this probably just the tip of the iceberg. There is a large cohort at risk of a heart attack without knowing it.
"A heart attack typically happens like this: Imagine turning on a tap and putting your finger to partially block the water flow. The water will gush out at a very high pressure and speed. By the same principle, if a segment of your artery is narrowed, at that narrowed part, the blood flows at high pressure and speed, adding a lot of stress to the lining of the wall. One day, when you are engaged in vigorous activity, the pressure increases, possibly severely enough to cause a tear in the wall lining ("plague rupture") exposing the cholesterol contents to the blood triggering a reaction. The body forms a clot to seal the tear, and the blood clot blocks the flow across the narrowed part o the artery, causing a heart attack in 10-15 minutes.
Are you at risk?
You won't know unless you undergo very thorough tests. But, you might save your life by heeding Dr Michael Lim's advice.
1. If you have not been exercising regularly, see your doctor before starting on a fitness programme or signing up for a marathon. This applies to any age. Get assessed as to whether you are at risk.
2. if you have multiple risk factors - the most important being high cholesterol levels; if you are diabetic, have high blood pressure; are a smoker, or have a strong family history of heart disease, ask your family doctor for a thorough screening.
3. Be aware that most heart attack patients do not get any warning sings. The key thin is prevention. Make lifestyle changes. Watch your diet, stop smoking, do moderate exercise.
The good news
With early detection, medical advances and a disciplined lifestyle, Dr Lim is optimistic about improvement in life span and quality of life. The trend now is to pick up disease early and manage it just by lifestyle changes and medication. There will be less need for surgical procedures and hospitalization. "It's possible for most people to live beyond 80, even to over 90. So, don't damage your knees. You can exercise that will affect your mobility in old age.
"The process of clogging of arteries can start as early your teens, but the good news is that heart attack and stroke are still highly preventable. Don't wait till your problem needs major treatment. Even if your arteries have narrowed, your risk of heart attack or stroke can be significantly reduced and the narrowing may even be partially reversible. For those at risk of a heart attack, because of strong family history, multiple risk factors or symptoms, there are highly accurate non-invasive tests which their family doctors can recommend. The good part of this is that patients will not be under- or over-treated. There's no guessing. We know for sure if there is a problem, and if there is a problem, we will be able to know the extent."
Stroke - High cholesterol and fats in the blood, high blood pressure and smoking can lead to atherosclerosis (thickening of arteries). A rupture of the thickened inner lining of an artery can provoke the formation of a blood clot, which in turn may break off and block blood supply to the brain.
Which test?
We won't consider the resting electrocardiogram (ECG) as a sensitive screening tool as it will only pick up patients who have had a heart attack but will not help us pick up most of those with disease but no damage to the heart muscles. Examples of other available tests (cost applies for private patients):
Treadmill, 60-70% accurate, $120 - $200
The patient walks on a treadmill while blood pressure and ECG (electrocardiogram) are monitored. The heart's response to exercise is evaluated to help detection of coronary blockages and heart rhythm abnormalities.
Dr Lim says, the layperson tends to settle for a treadmill test because it's common and cheap. "But be aware that if your treadmill test result is negative, it doesn't mean you are not at risk of getting a heart attack. It just tells you that you don't have a serious (above 70%) blockage. But your arteries might be 40-60% blocked, so don't think you are absolutely fit. Your family doctor will advise you whether you require further evaluation."
Nuclear Myocardial Perfusion, over 80% accurate, may be recommended after a treadmill test detects abnormality, $450 - $600
This imaging test is to check how well blood flows to the muscle. The patient is made to exercise on a treadmill or bicycle. When the patient reaches his maximum level of exercise, a small amount of radioactive substance called thallium is injected into the bloodstream. Special photos taken will show the flow of blood (mixed with thallium) into the heart. After a couple of hours rest, another series of pictures are taken. If blood flow is normal during rest but not during exercise, it may indicate a blockage in one or more coronary arteries. If the test is abnormal during both rest and exercise, the problem is worse, and if no thallium is seen in some part of the heart muscle, this part is dead from a prior heart attack.
Invasive Coronary Angiogram, close to 100% accuracy depending on experience of operator; currently used as the gold standard, $2500 - $3200
An x-ray of the heart is taken to see if arteries are narrowed or blocked. A catheter (thin, hollow plastic tube) is threaded through the aorta (largest artery in your body) until it reaches the coronary arteries. A special contrast dye is injected and x-rays are taken of the blood vessels as the dye moves through them.
Apart from diseased arteries, an angiogram can also detect heart problems like aneurysm (abnormal ballooning of the heart wall), heart arrhythmia (irregular heart beat) and birth defects like a hole in the heart. Obviously, an uncomfortable and inconvenient procedure.
Angina is the chest pain or discomfort caused by a lack of oxygen to the heart muscle, due to a narrowing of the coronary arteries. The pain may be brought on by exertion or emotional upset, and usually disappears with rest and medication. The episode does not cause permanent damage to the heart, but in some cases, can lead to a heart attack.
CT Coronary Angiogram using a Multidetector Computed Tomography Scanner (MDCT), accuracy depends on the experience of the centre, accuracy can be as high as 90-99% with an experienced operator, $1000 - S$1300
From four-slice detectors to 64-slice simultaneous detectors, CT scanning has come a long way. While older scanners only created good images int he axial plane, like a standard loaf of bread, the newest version can 'slice' the patient in any plane (front to back), side to side or anything in between. Plus, the data can be used to create 3D images of the internal organs. Excellent for advanced cardiovascular imaging plus scanning time is fast (seconds).
A heart attack occurs when a narrowed coronary artery is blocked by a blood clot, stopping blood from reaching some parts of the heart. This can severely damage the affected heart muscle and if blood flow is not restored quickly, that part of the heart muscle dies.
Dr Michael Lim is of the opinion that MDCT scanning for the middle-aged who are at risk for heart disease may be potentially beneficial because "it's non-invasive, a convenient outpatient test, and in experienced hands, gives accuracy comparable to invasive Coronary Angiography technology has made it possible to see arteries in virtually any plane, and it has made a difference to the way we manage heart disease."
"In our management strategy, our main focus is on prevention. For most of the patients who are detected with narrowing of their heart arteries as a result of accumulation of cholesterol, in the first three months, we use a combination of lifestyle changes and medication to drop their LDL levels to below 70 mg/dl. By maintaining this level, by and large, we have successfully lowered the risk of a heart attack. Many of our patients who originally would have been considered for bypass surgery or a stent did not require a procedure after aggressive preventive treatment." For more serious blockages which do not respond to preventive treatment, Dr Lim uses the stent (scaffolding-like support in the weakened artery) or recommends bypass surgery. Dr Lim advises patients to check with their family doctors as to what tests are appropriate for them.
Picture of health
"We have one of the largest experience in the world with CT Coronary Angiography using MDCT technology, putting us ahead of even top centres in the U.S. and Europe," Dr Lim says. "The new CT machines are so advanced that the key limiting factor in accuracy is no longer that of the limitation of the technology of the machines. The level of accuracy depends more on the way you scan and process information, and the experience of the medical staff."
He feels it saves people money in the long run. "If the scan doesn't show anything significant, you probably don't need another one for five years. In our practice, we have replaced invasive angiograms with CT coronary angiograms. Invasive coronary angiograms are more costly, and riskier as a tube is put into the body and the heart arteries are opened. Once diagnosed, a patient can start on lifestyle changes and get their medication from their family doctors or regular polyclinic doctors. You incur a cost for the certainty of diagnosis, but beyond that, the cost of maintaining your health is minimal."
A picture does put reality in front of you. "When you tell people you have to change your lifestyle, they can't be bothered. But when they are able to see with their own eyes that the problem is real and happening to them, then it makes a big difference."
Contrary view But as with everything in medicine, there is always more than one school of thought. While CT coronary angiogram is gradually gaining acceptance as a preferred diagnostic test of choice for diseased heart arteries in many centers around the world, some Singapore cardiologists are wary about recommending CT coronary angiogram as the radiation and the dye used is similar to that of an invasive coronary angiography, like invasive coronary angiography, requires the use of x-rays and injection of contrast dye to obtain pictures of the heart arteries. Hence, as generally agreed by all cardiologists, you should seek the opinion of your family doctor. However, do read up and ask around.
Dr Michael Lim is Senior Consultant Cardiologist and Medical Director of the Singapore Heart, Stroke & Cancer Centre, Ngee Ann City, tel: 6881 8811.
Medical Milestones for Singapore, Heart, Stroke & Cancer Centre
1995 - Dr Michael Lim, the first doctor in Asia to perform carotid artery stenting
2004 - Reference Centre in the Asia-Pacific region for MDCT technology for Philips Medical Systems
2006 - The first centre in an Asia-Pacific country to have a scientific paper demonstrating comparable accuracy of CT coronary angiogram with invasive coronary angiogram published in a major medical journal. |
