Cardiac Stress Test or CPX test is a cardiological test that measures the heart’s ability to respond to external stress in a controlled clinical environment. The stress response is induced by exercise or by drug stimulation.

The stress test is done with heart stimulation, either by exercise on a treadmill, pedaling a stationary exercise bicycle ergometer, or with intravenous pharmacological stimulation, with the patient connected to an electrocardiogram (ECG). People who cannot use their legs may exercise with a bicycle- like crank that they turn with their arms.

The level of stress is progressively increased by adjusting the difficulty (steepness of the slope) and speed. The test administrator or attending physician examines the symptoms and blood pressure response. With use of ECG, the test is most commonly called a cardiac stress test but is known by other names, such as exercise testing, stress testing treadmills, exercise tolerance test, stress test or stress test ECG.

A stress test may also use an echocardiogram (ultrasonic imaging of the heart) or a nuclear stress test ( In which a radioisotope is injected into the bloodstream).

A stress test may be accompanied by echocardiography. The echocardiography is performed both before and after the exercise so that structural differences can be compared.