| Cardiac stress test | |
|---|---|
| Intervention | |
A male patient walks on a stress test treadmill to have his heart's function checked |
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| ICD-9-CM | 89.4 |
| MeSH | D025401 |
Cardiac stress test (or Cardiac diagnostic test) is a test used in medicine and cardiology to measure the heart's ability to respond to external stress in a controlled clinical environment.
The stress response is induced by exercise or drug stimulation. Cardiac stress tests compare the coronary circulation while the patient is at rest with the same patient's circulation observed during maximum physical exertion, showing any abnormal blood flow to the heart's muscle tissue (the myocardium). The results can be interpreted as a reflection on the general physical condition of the test patient. This test can be used to diagnose ischemic heart disease, and for patient prognosis after a heart attack (myocardial infarction).
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The cardiac stress test is done with heart stimulation, either by exercise on a treadmill, pedalling a stationary exercise bicycle ergometer[1] or with intravenous pharmacological stimulation, with the patient connected to an electrocardiogram (or ECG).
People who cannot use their legs may exercise with a bicycle-like crank that you can turn with your arms.[2]
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 be accompanied by echocardiography.[1] The echocardiography is performed both before and after the exercise so that structural differences can be compared.
Typically, a radiotracer (Tc-99 sestamibi or Tl-201) may be injected during the test. After a suitable waiting period to ensure proper distribution of the radiotracer, photos are taken with a gamma camera to capture images of the blood flow. Photos taken before and after exercise are examined to assess the state of the coronary arteries of the patient.
Showing the relative amounts of radioisotope within the heart muscle, the nuclear stress tests more accurately identify regional areas of reduced blood flow.
Stress and potential cardiac damage from exercise during the test is a problem in patients with ECG abnormalities at rest or in patients with severe motor disability. Pharmacological stimulation from vasodilators such as dipyridamole or adenosine, or positive chronotropic agents such as dobutamine can be used. Testing personnel can include a cardiac radiologist, a nuclear medicine physician, a cardiologist, and/or a nurse.
The American Heart Association recommends ECG treadmill testing as the first choice for patients with medium risk of coronary heart disease according to risk factors of smoking, family history of coronary artery stenosis, hypertension, diabetes and high cholesterol.
The common approach for stress testing by American College of Cardiology and American Heart Association indicates the following: [2]
(Sensitivity is the percentage of sick people who are correctly identified as having the condition. Specificity indicates the percentage of healthy people who are correctly identified as not having the condition.)
The value of stress tests has always been recognized as limited in assessing heart disease such as atherosclerosis, a condition which mainly produces wall thickening and enlargement of the arteries. This is because the stress test compares the patient's coronary flow status before and after exercise and is suitable to detecting specific areas of ischemia and lumen narrowing, not a generalized arterial thickening.
According to American Heart Association data, about 65% of men and 47% of women have as their first symptom of cardiovascular disease a heart attack or sudden cardiac arrest. Stress tests, carried out shortly before these events, are not relevant to the prediction of infarction in the majority of individuals tested. Over the past two decades, better methods have been developed to identify atherosclerotic disease before it becomes symptomatic.
These detection methods have included either anatomical or physiological.
The anatomic methods directly measure some aspects of the actual process of atherosclerosis itself and therefore offer the possibility of early diagnosis, but are often more expensive and may be invasive (in the case of IVUS, for example). The physiological methods are often less expensive and more secure, but are not able to quantify the current status of the disease or directly track progression.
Absolute contraindications to cardiac stress test include:
Side effects from cardiac stress testing may include
The choice of pharmacologic stress agents used in the test depends on factors such as potential drug interactions with other treatments and concomitant diseases.
Pharmacologic agents such as Adenosine, Lexiscan (Regadenoson), or dipyridamole is generally used when a patient cannot achieve adequate work level with treadmill exercise, or has poorly controlled hypertension or left bundle branch block. However, a exercise stress test may provide more information about exercise tolerance than a pharmacologic stress test.[3]
Commonly used agents include:
Lexiscan (Regadenoson) or Dobutamine is often used in patients with severe reactive airway disease (Asthma or COPD) as adenosine and dipyridamole can cause acute exacerbation of these conditions. If the patient's Asthma is treated with an inhaler then it should be used as a pre-treatment prior to the injection of the pharmacologic stress agent. In addition, if the patient is actively wheezing then the physician should determine the benefits versus the risk to the patient of performing a stress test especially outside of a hospital setting.
Aminophylline may be used to attenuate severe and/or persistent adverse reactions to Adenosine and Lexiscan.
The stress test does not detect:
The test has relatively high rates of false positives and false negatives compared with other clinical tests.
Once the stress test is completed, the patient generally is advised to not suddenly stop activity, but to slowly decrease the intensity of the exercise over the course of several minutes.
Cardiac
Cardiac arrest
Harvard Step Test
Metabolic equivalent
Robert A. Bruce