Myths and Facts About Cardiovascular Disease and Health - Part 1
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Preventing or predicting heart disease is dependent on a number of factors, including nutrition and exercise. Heart health screenings are another important factor in diagnosing risk factors for heart disease.
Unfortunately, patients often experience uncertainty or anxiety about heart disease screenings. Many times, anxiety or fear about a particular medical screening is simply the result of misinformation or believing a myth about the test in question. Medical myths can arise when patients don’t understand what a particular test can and can’t tell and what the procedure involves.
In honor of American Heart Month, Cooper Clinic Director of Clinical Research, Nina Radford, MD, dispels two common myths in cardiovascular disease risk prevention in this two-part series.
Myth #1: A normal stress test is a bulletproof vest.
In a person without a history of cardiovascular disease, a treadmill stress test may be performed for a number of reasons, including:
To assess the presence of coronary artery disease (coronary artery blockages)
To determine functional capacity
To evaluate exercise related symptoms or to create an exercise prescription
In broad terms, the rationale of the exercise stress test is to increase the work of the cardiovascular system and evaluate whether the cardiovascular system responds normally. A number of parameters are evaluated in terms of classifying a treadmill stress test as normal:
Changes on the EKG
Worrisome exercise-related symptoms
Heart rate response at peak exercise and following the first minute of recovery
Blood pressure response during exercise and the development of heart rhythm abnormalities
If all of these parameters are normal in an individual, then the risk of that patient suffering a cardiac event in the next five to 10 years is low compared to someone with abnormal results. However, it is important to remember that a low-risk result of a normal treadmill test is never a no-risk result.
Why? First and foremost, the treadmill stress test is not a perfect risk prediction tool. The “sensitivity” of the test (having a positive or abnormal test in the setting of serious blockages) is not 100 percent accurate, but closer to 70 percent. It is possible that there could be a significant blockage that is not detected by the test. Perhaps the blockage is in a small artery, or other heart arteries adapted to provide flow to the compromised area of blood flow.
The “gold standard” for detecting blockages is “ST segment” change on the EKG. However, some studies suggest that low exercise capacity or poor heart recovery after exercise may be more important markers of significant coronary disease than changes on the EKG. This can be a tough measurement to sort out.
Is someone’s function capacity low because they are couch potatoes or because they have blockages? Sometimes they just need to start a gradual exercise program and see if there functional capacity improves in order to sort this out.
Another critical factor is that a treadmill stress test will only detect the presence of a significant coronary blockage that is limiting blood flow during exercise (so called obstructive blockage of about 70 percent or more). An individual could have five 30 to 40 percent coronary blockages and still return normal results from a treadmill stress test.
If a patient’s risk factors are not well controlled, one of those non-obstructive blockages could rupture and cause a heart attack. Let’s take “Uncle Joe” for example. The results of his stress test were completely normal, yet a week after his test, Uncle Joe suffered a heart attack. His heart attack was the result of plaque that ruptured, the cause of which might have been because his risk factors were not under good control, he experienced a very stressful event or he was not exercising regularly and then went out and shoveled three feet of snow out of his driveway.
The bottom line is that when when assessing a patient’s cardiac risk, the treadmill stress test results are only a piece of the puzzle. The results must be factored in with family history, risk factor assessment, clinical history and a physical examination to determine the patient’s risk of a coronary event such as a heart attack.
If your doctor has ordered a treadmill stress test, talk to him/her what the test entails, what it can tell you and what its limitations are. Without that information, you may be susceptible to believing myths about the treadmill stress test. Once you know the facts you can put the information from those test into perspective. Stay tuned for Dr. Radford's Myth Busters: Cardiovascular Disease - Part 2.
Article provided by Cooper Aerobics Marketing and Communications.