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Dr. Graham Wong, VGH,Cardiologist, Vancouver, BC attended medical school and completed his internal medicine residency at the University of British Columbia, then completed his fellowship training in cardiology at McGill University.Dr. Graham Wong, Cardiologist, Vancouver, BC pursued a two-year research fellowship at the Brigham and Women’s Hospital with the TIMI Group, with a focus on clinical trials of acute coronary syndromes and completed his MPH at the Harvard School of Public Health.
Dr. Graham Wong, Cardiologist, Vancouver, BC is also board certified by the Society of Cardiovascular Computed Tomography. Dr. Graham Wong, Cardiologist, Vancouver, BC is currently the Clinical Director of the Coronary Care Unit at Vancouver General Hospital and is a Clinical Associate Professor of Medicine at UBC.
Dr. Graham Wong, VGH,Cardiologist, Vancouver, BC is the Medical Co-Director of the Regional STEMI Planning Committee for the Vancouver Coastal Health Authority on Acute Coronary Care. Dr. Graham Wong, Cardiologist, Vancouver, BC is also involved in medical education and sits on the Postgraduate Committee for the UBC Cardiology training program and is an examiner for the Royal College of Physicians and Surgeons of Canada. Dr. Graham Wong, Cardiologist, Vancouver, BC current research interests include risk stratification for acute coronary syndromes and appropriate use of cardiac CT angiography.
Dr. Graham Wong, Cardiologist, Vancouver, BC MD MPH FRCPC FACC Director, Coronary Care Unit Vancouver General Hospital Regional Medical Lead, Acute Cardiac Care Vancouver Coastal Health Authority/Providence Health Care Clinical Associate Professor of Medicine University of British Columbia
Dr. Graham Wong, MD, MPH, FRCPC, FACC, Cardiologist, discusses how atrial fibrillation is linked to stroke and why it’s so important for patients to be compliant when taking blood thinners.
Atrial fibrillation is the most common rhythm problem in the world. It can affect anybody, although it does tend to cluster in people who are a little bit older and those with high blood pressure.
The symptoms of atrial fibrillation speak to the irregular electrical stimulation of the heart, as opposed to a single dominant electrical signal, and so patients can feel an irregular heartbeat subjectively felt as palpitations.
Because the electrical instability of atrial fibrillation causes the heart to beat irregularly the blood flow in that heart becomes irregular, and the current thinking is that the irregular flow of blood in a heart under the control of atrial fibrillation can form little eddy currents and the blood can become static.
And when blood becomes static and becomes sluggish it can form little blood clots, and if those blood clots then leave the heart and lodge up in the brain, that can cause the most dreaded complication of atrial fibrillation, which is stroke.
The risk of stroke with atrial fibrillation is not the same for any individual. And the more we understand atrial fibrillation, the more we realize that it’s not the atrial fibrillation itself that causes the stroke, it’s the company in which it keeps.
And so when we are faced with a patient with atrial fibrillation, what we try to do is estimate the risk of a stroke by looking for the other risk factors that we know that when they coexist with stroke, will increase to a point where we would need to consider starting patients on blood thinners.
Some of these risk factors that will increase your risk of stroke in the company of atrial fibrillation include increasing age, female gender, high blood pressure – treated or otherwise, diabetes – treated or otherwise, congestive heart failure – otherwise known as water on the lungs, and the presence of a prior stroke.
What clinicians do is they add up these risk factors in an ordinal fashion. And if you have more than one risk factor, we believe that your perceived risk of stroke is high enough that we would normally recommend blood thinners to minimize or reduce that risk.
The risk of stroke is in no way related to whether or not patients feel their atrial fibrillation or are asymptomatic, and up to 30% of patients with atrial fibrillation have no idea that their rhythm is irregular. And so the absence of symptoms in no way protects you from the risk of a stroke.
Your doctor may suggest several choices for blood thinners depending on your perceived risk of stroke. These would include aspirin, Warfarin or some of the newer agents which we call the direct-acting or novel anticoagulants.
For several decades Warfarin was the gold standard in terms of our choice of blood thinner. It’s been shown to be highly effective at reducing the risk of stroke, and reasonably safe. The problem with Warfarin is it’s a very unreliable drug insofar that it binds to all sorts of proteins and other materials in the body, and needs to be monitored and regulated quite closely.
So patients on Warfarin need to go for regular blood tests and their doses need to be increased or decreased depending on the level of Warfarin. In addition, Warfarin is influenced by other drugs, food and drink, and so it’s very difficult to maintain a therapeutic dose of Warfarin, and patients find that going to the lab is often very inconveniencing for them.
Recently, a newer class of blood-thinning drugs has been introduced that have found to be superior to Warfarin, unlike Warfarin do not interfere with food or drink, can be taken once or sometimes twice a day, and do not require monitoring and can be taken on a fixed dosing schedule.
These drugs have much less risk of bleeding in the head, and either an equivalent or lower risk of total bleeding with at least an equivalent reduction in stroke compared to Warfarin, and are now considered the preferred agents for blood thinning amongst patients with atrial fibrillation.
It’s very important that if patients are prescribed blood thinners for the purposes of reducing stroke, that they must take their medications as scheduled and as recommended by their doctors. Missing even one or two doses could put you at risk for a stroke, because these blood thinners need to be at a certain level in your body for them to be effective.
There are things you can do to minimize the chance you will develop atrial fibrillation by adopting healthier lifestyle choices. We know that one of the biggest predictors of atrial fibrillation is high blood pressure, and so anything you can do to reduce your blood pressure, either with pharmacological or non-pharmalogical interventions, can potentially reduce your risk of developing atrial fibrillation as a consequence.
If you have any additional questions regarding atrial fibrillation and stroke prevention, I would strongly urge you to speak to your family physician, stroke neurologist or local internist or cardiologist.
Presenter: Dr. Graham Wong, Cardiologist, Vancouver, BC
Local Practitioners: Cardiologist
Dr. Graham Wong, MD, MPH, FRCPC, FACC, Acute Cardiac Care, Cardiologist, talks what a stress test is and how it can help diagnose cardiac conditions.
A stress test is one of the most commonly used cardiovascular diagnostic tests. There are many reasons why people would reach for a stress test, and why a stress test is useful. At its heart, a stress test is an assessment of someone’s physiological or aerobic reserve, and a fairly good assessment of a person’s hemodynamic and circulatory response to exercise.
Using this test we can assess someone’s fitness level, and whether or not there are any limiting sub-systems in the heart—whether it’s the electrical system or the arterial system that might limit someone’s ability to exercise.
On a treadmill examination, where you’re able to accurately assess one’s blood pressure, one’s heart rate, and in this way we can understand your blood pressure and heart rate response to exercise, and we can very objectively assess how much aerobic work you’re performing with a series of very graded algorithms.
The most common algorithm that’s used on a treadmill is something called the BRUCE protocol. At its heart, a treadmill examination is an electrical test that looks at changes in an electrical signal—the electric cardiogram, and to determine if there are any changes that would reflect problems with the electrical sub-system, or more commonly, indirect signs that can suggest there’s something wrong with the circulatory system.
Please note that the treadmill examination is limited to our ability to look at the electrical sub-system of the heart as well as the onset of any clinical symptoms that might be reproduced with exercise, such as chest pain or shortness of breath. Although a treadmill test is—at its very nature—an electrical test, the most commonly-used reason for a treadmill is to sort of infer the health of the circulatory system, to look for problems with plugged arteries or atherosclerosis.
But please note that the treadmill examination actually does not allow us to look at the arteries themselves, what we are trying to do is infer a problem with the arteries, if there are abnormalities in the treadmill test, by looking at changes in the ECG with exercise, that may come about as a result of impaired blood flow from a blocked artery.
Because of this limitation, treadmill examinations can be wrong, and there is up to a one-third chance of what we call a false positive, and so what people need to understand that not everyone should get a treadmill examination, and that the selection of patients for treadmill examination is very important, in order to make sure that the answers that we get and the accuracy of the treadmill is as good as we can make it.
Another less common, but very important indication for using the treadmill examination would be to understand the hemodynamic response of patients with valve problems, to understand whether or not the valve has degraded or deteriorated to the point where it impairs aerobic function and physiological function, and that would give some evidence potentially that a patient is at the point where a valve needs to be replaced.
So if you have any further questions about treadmill testing, I would invite you to speak to your family physician, or your specialist who performs treadmills.
Presenter: Dr. Graham Wong, Cardiologist, Vancouver, BC
Local Practitioners: Cardiologist