Health Tips

No medical test is 100% predictive. The stress test - while still a tried-and-true way to screen for heart problems - is far from foolproof, and it shouldn't be viewed as providing the final word on your risk for having a heart attack.
The typical stress test involves walking on a treadmill while an electrocardiogram machine measures the electrical activity of the heart as it contracts and relaxes. The graphical pattern of the electrocardiogram (ECG) reveals clues that blood flow through the coronary arteries supplying the heart muscle may not be providing the oxygen and the energy the muscle needs when it is working hard.
Atherosclerosis - the condition that narrows the coronary and other arteries in the body and therefore slows blood flow - is the result of plaques in the walls of the arteries. Each plaque is a swollen, fat-filled little pouch with a fibrous cap that holds the contents in.Some plaques are small and therefore don't obstruct the flow of blood very much, making it possible for some people to "pass" a stress test with no problems. However, the fibrous caps on plaques aren't always sturdy. If a fragile fibrous cap ruptures, pouring fat into the middle of the artery just above the plaque, a clot forms and blocks blood flow, potentially causing a heart attack. Plaques can rupture at any time, even a few days after someone has taken a stress test.
Doctors are still working on tests that will spot fragile, or "vulnerable" plaques and on treatments to make plaques less likely to rupture.