Cardiac stress tests

Cardiac stress test
Intervention
A male patient walks on a stress test treadmill to have his heart's function checked.
ICD-9-CM	89.4
MeSH	D025401
MedlinePlus	003878
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A cardiac stress test (or cardiac diagnostic test) is a cardiological test that measures a heart's ability to respond to external stress in a controlled clinical environment. The stress response is induced by exercise or by drug stimulation.

Cardiac stress tests compare the coronary circulation while the patient is at rest with the same patient's circulation during maximum physical exertion, showing any abnormal blood flow to the myocardium (heart muscle tissue). The results can be interpreted as a reflection on the general physical condition of the test patient. This test can be used to diagnose coronary artery disease (also known as ischemic heart disease) and assess patient prognosis after a myocardial infarction (heart attack).

The cardiac stress test is done with heart stimulation, either by exercise on a treadmill, pedalling 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 mechanical 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.

A resting echocardiogram is obtained prior to stress. The images obtained are similar to the ones obtained during a full surface echocardiogram, commonly referred to as transthoracic echocardiogram. The patient is subjected to stress in the form of exercise or chemically (usually dobutamine). After the target heart rate is achieved, 'stress' echocardiogram images are obtained. The two echocardiogram images are then compared to assess for any abnormalities in wall motion of the heart. This is used to detect obstructive coronary artery disease.