Heart disease is a strange animal indeed. Our very first symptoms can range from mild shortness of breath on exertion to sudden death – and almost every possible symptom in between. My own were those of the textbook Hollywood Heart Attack (crushing central chest pain, nausea, sweating, and pain down my left arm) – yet I was sent home by Emergency Department staff with a misdiagnosis of indigestion – feeling very, very embarrassed for having made such a fuss over nothing. It took two weeks to be finally correctly diagnosed with myocardial infarction (heart attack) caused by a 95% blockage of my Left Anterior Descending Coronary artery. And it took several more months – and another trip back to hospital – to figure out what was causing ongoing distressing symptoms that were ultimately diagnosed as Inoperable Coronary Microvascular Disease (MVD) or dysfunction of the smaller coronary arteries.
But MVD is very tricky to diagnose because most standard coronary artery disease diagnostic tests – the kind that work so well at identifying big fat blockages in our larger arteries – may not be capable of catching it.
The characteristics of MVD include:
- A build-up of plaque that spreads evenly throughout the walls of the small arteries. So while there may be no obvious blockages, blood flow to the heart is still reduced. (MVD is also called Non-Obstructive Coronary Artery Disease).
- Vessels that don’t expand or dilate properly during physical or emotional stress.
- Vessels that spasm (contract) abnormally.
Treatment goals for MVD are three-fold: stop it from getting worse, improve quality of life by relieving symptoms, and prevent a heart attack.
Standard invasive treatments for coronary heart disease – like angioplasty, stenting and bypass surgery – are not used to treat coronary MVD. Instead, treatment focuses on reducing risk through managing underlying conditions.
Unlike coronary artery disease in which angina symptoms are often brought on during exertion, symptoms of MVD are often first noticed during routine daily activities and times of mental stress.
A questionnaire called the Duke Activity Status Index may be useful. Developed by Duke University cardiologist Dr. Mark A. Hlatky (and published in the American Journal of Cardiology), this questionnaire can measure our functional capacity by correlating simple daily activities with peak oxygen uptake required to complete these activities. It offers information about how well blood is flowing through our coronary arteries, and also helps doctors select appropriate next steps.
Duke Activity Status Index
|Can you take care of yourself (eating, dressing, bathing, etc.)?||0.8|
|Can you walk around your house?||0.5|
|Can you walk a block or two on level ground?||0.8|
|Can you climb a flight of stairs or walk up a hill?||1.6|
|Can you run a short distance?||2.3|
|Can you do light work around the house (washing dishes, etc.)?||0.8|
|Can you do moderate work around the house (sweeping, carrying groceries, etc.)?||1.0|
|Can you do heavy work around the house (scrubbing floors, moving heavy furniture, etc.)?||2.3|
|Can you do yard work (raking leaves, pushing a mower, etc.)?||1.3|
|Can you have sexual relations?||1.5|
|Can you participate in moderate recreational activities (golf, dancing, etc.)?||1.7|
|Can you participate in strenuous sports (swimming, singles tennis, skiing, etc.)?||2.1|
|Circle the points for a question only if you can answer “Yes, with no difficulty”. Add up the circled points. The lower the score, the greater the risk. Total scores of 4.7 or below are considered higher risk.|
If I had been administered this Duke Activity Status Index at the beginning of my earliest symptoms, my score would have been relatively respectable at 6.8 points. In between debilitating bouts of these increasingly frightening cardiac symptoms, I spent two full weeks taking care of my daily needs (eating, dressing, bathing). I could walk around the house. I could cook meals and do the dishes afterwards. I could drive. I could go to work, attend meetings, make decisions, complete deadline projects, participate in important phone calls. I could even get on a plane and fly across the country to Ottawa for my mother’s 80th birthday weekend. By then, I was definitely having a profoundly more difficult time each passing day in keeping up the pretense that everything was “Fine, just fine!” while popping antacids for my “acid reflux” diagnosis, trying to cope with increasingly frequent attacks of cardiac symptoms, closer and closer together.
I was in fact experiencing what Irish researchers have described as the “slow onset myocardial infarction“, a reality that their studies identified in over 60% of heart attack survivors. Unlike that high-drama Hollywood Heart Attack we often imagine, people suffering slow-onset symptoms can wait dangerously longer than they should (believing symptoms to be “nothing serious” because they don’t match their expectations of what a “real” heart attack looks like). In fast-onset heart attacks, however, patients do seek emergency help faster because severe symptoms convince them that “this IS serious!”
But after I somehow survived that cross-country return flight home to the West Coast from Ottawa and returned once again to that Emergency Department, my Activity Status score would have been a dangerous 2.9 on the Duke scale.
A great deal remains to be learned about MVD, especially in women.
There are some basic strategies that you can use to help arrive at an accurate diagnosis and the best possible medical care.
For example, because the Duke Scale looks at physical tasks only instead of emotional stressors, it can miss the considerable link between psychosocial triggers that can make MVD symptoms far worse.
Cardiologist Dr. Puja K. Mehta, director of the Non-Invasive Vascular Function Research Lab at the Barbra Streisand Women’s Heart Center in Los Angeles, explains:
“We know that women who have chest pain and reduced oxygen to the heart – in the absence of ‘male-pattern’ obstructive coronary artery disease – may experience microvascular dysfunction during times of emotional distress even though their heart rates stay relatively low.
“More specifically, we hypothesize that emotional stress may trigger microvascular dysfunction and lead to heart attacks and other cardiac problems in women.”
Listen to your body and believe in your instincts. If you feel strongly that something is wrong but your doctor can’t find a problem, get a second opinion. Find a specialist who is familiar with Coronary Microvascular Disease. Ask questions. If you don’t fully understand the answers, ask more questions until you do.
Meanwhile, here are some other diagnostic tests for identifying coronary microvascular disease according to the useful medical site, Second Opinion:
- Adenosine Coronary Flow Reserve and Acetylcholine Endothelial Function Test with Cardiac Magnetic Resonance Imaging (MRI)
This is a pharmacological stress test. During the two-step test, the drug adenosine, which causes the small vessels of the heart to dilate, is injected into one of the coronary arteries and the amount of blood flow is measured. Next, the drug acetylcholine, which causes dilation in the large arteries, is injected and the amount of blood flow is again measured. The superior resolution of magnetic resonance imaging is used to get images of the beating heart and to look at its structure and function. MRIs can show poor blood supply to the innermost areas of the heart and can detect changes in the small coronary blood vessels. If either test shows decreased blood flow to the heart muscle, a diagnosis of microvascular disease can be made.
- Dipyridamole Positron Emission Tomography (PET)
This cardiac PET scan also shows how much blood flow the heart receives at rest and under stress. During the first stage, fluorodeoxyglucose is administered while the patient is at rest. The images that are produced from this first PET scan are checked with a second PET scan after the patient is administered dipyridamole, a drug that produces an effect in the body similar to the effects of strenuous exercise.
Doppler Wire Coronary Angiogram
The most definitive test for microvascular disease is a special type of coronary angiogram used to measure coronary artery flow reserve or coronary reactivity. It involves threading an ultra-thin wire with blood-flow sensors at the tip deep into a coronary artery (called cardiac catheterization). Blood flow in the artery is then measured before and after injections of one or more medications to cause the microvessels to dilate. The smaller the change in pressure and flow, the stiffer the vessels. This test is done only at a small number of cardiac centres. Cardiac catheterization procedures are invasive and expensive, but the risks of doing them have to be weighed against the risks of not being accurately diagnosed.
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