This is a story worth listening to, more so if you have undergone a stress test on the treadmill to check your heart condition and have got a negative result. Senior cardiologist Dr. Balbir Singh of the Apollo Hospitals in New Delhi narrates, “This is about my professor at All India Institute of Medical Sciences. Some years ago, on feeling somewhat uncomfortable, the professor, a cardiologist, went for a stress test. Much to his relief, it turned out to be negative. But just two weeks after the test, he suffered a heart attack.”
Dr. Singh’s rationale is, “It ran in his family. So even if a stress test shows negative, you need to look at the symptoms too, such as your cholesterol level, your lifestyle, etc. and also whether there is a heart condition in the family.”
But five years after the American Heart Association established that stress tests may fail to identify irregularities of the heart in patients, and cardiologists worldwide are convinced the technique has serious limitations, few people here are aware of the limits of the test. Almost always, a negative stress test frees a patient of any fear of cardiac problems, and a positive result invariably triggers panic.
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But Dr. Singh highlights, “A stress test can have false positive or false negative results.” He elaborates on when to worry: “A patient need not worry much about a negative stress test result only if he/she is asymptomatic — that is, if he/she shows no possible symptoms of a heart condition. But if they do, or have already had a heart attack, a negative stress test doesn’t mean they are safe. They still need to do an angiogram.”
This is particularly important in the case of women. “Many women, even after the ECG shows irregularities of the heart or otherwise, show negative during a stress test for non-specific causes. It is better to go for a stress echo.” During stress echo, a small prop is put on the patient while he/she runs on the treadmill to reap accurate results.
If an asymptomatic person shows the stress test as positive, he/she should ideally go for a stress echo or a stress thallin test before undergoing an angiogram straightaway to establish his/her heart condition. A stress thallin is a more expensive proposition but is far more accurate than a common stress test, as it uses radio-nuclear material.
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For the layman, Dr. Singh explains how a stress test works. “A stress test puts the heart to stress as you start running on the treadmill. During the test, both blood pressure and heart rate go up, thus facilitating blood flow to the heart. But if there is an arterial blockage, then the blood flow will be less. But mind you, it picks up a blockage only if it is 75 per cent blocked.” However, an angiogram shows up even 55 per cent blockage of the artery.
If the stress test is not always accurate, why do doctors then ask patients to undergo one? He responds, “Like an ECG, it has its importance, particularly in asymptomatic persons. Also, since Indians are more prone to heart disease, we don’t recommend bypass surgery if the blockage is below 75 per cent.”
While a stress echo takes about an hour and costs Rs.4,000, a stress thallin test takes about five to six hours and is priced at Rs.8,000.