stress test

A cardiac stress test deliberately makes the heart work harder and watches for signs that its blood supply cannot keep up. The idea is simple: a coronary narrowing may pass unnoticed at rest, because flow is still adequate when demand is low, but reveals itself when the heart is pushed and the constricted artery can no longer deliver enough blood. Stress unmasks what rest can hide.

The stress can be physical or chemical. Exercise on a treadmill or bicycle raises heart rate and demand naturally and is preferred when a patient can exert. For those who cannot, drugs substitute: dobutamine speeds and strengthens the heart, while vasodilators such as adenosine or regadenoson widen normal arteries so a diseased vessel stands out by comparison. During the stress, the heart is monitored — by ECG alone, or with imaging layered on top, such as echocardiography or nuclear perfusion scanning, which see the consequences of inadequate flow directly.

A stress test assesses the functional significance of coronary disease — whether a narrowing actually limits flow under load — rather than simply picturing the arteries. It is most useful in patients at intermediate risk. Like any test it can mislead: false positives and false negatives occur, and a normal result lowers but does not abolish risk. The choice of stressor and imaging is tailored to the individual patient.