Cardiac stress test
Encyclopedia
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
).
(or ECG).
People who cannot use their legs may exercise with a bicycle-like crank that you can turn with your arms.http://www.livestrong.com/article/373962-treadmill-stress-test-exercises/
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.
. The echocardiography is performed both before and after the exercise so that structural differences can be compared.
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.
(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.
Examples of anatomical methods include:
Examples of physiological methods include:
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.
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.
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 test has relatively high rates of false positives and false negatives compared with other clinical tests.
Cardiac arrest
Harvard Step Test
Metabolic equivalent
Robert A. Bruce
Medicine
Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....
and cardiology
Cardiology
Cardiology is a medical specialty dealing with disorders of the heart . The field includes diagnosis and treatment of congenital heart defects, coronary artery disease, heart failure, valvular heart disease and electrophysiology...
to measure the heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
's ability to respond to external stress
Stress (biology)
Stress is a term in psychology and biology, borrowed from physics and engineering and first used in the biological context in the 1930s, which has in more recent decades become commonly used in popular parlance...
in a controlled clinical environment.
The stress
Stress (biology)
Stress is a term in psychology and biology, borrowed from physics and engineering and first used in the biological context in the 1930s, which has in more recent decades become commonly used in popular parlance...
response is induced by exercise or drug
Drug
A drug, broadly speaking, is any substance that, when absorbed into the body of a living organism, alters normal bodily function. There is no single, precise definition, as there are different meanings in drug control law, government regulations, medicine, and colloquial usage.In pharmacology, a...
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
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
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
Myocardial infarction
Myocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...
).
Cardiac stress test
The cardiac stress test is done with heart stimulation, either by exercise on a treadmill, pedalling a stationary exercise bicycle ergometerhttp://www.nlm.nih.gov/medlineplus/ency/article/003878.htm or with intravenous pharmacological stimulation, with the patient connected to an electrocardiogramElectrocardiogram
Electrocardiography is a transthoracic interpretation of the electrical activity of the heart over a period of time, as detected by electrodes attached to the outer surface of the skin and recorded by a device external to the body...
(or ECG).
People who cannot use their legs may exercise with a bicycle-like crank that you can turn with your arms.http://www.livestrong.com/article/373962-treadmill-stress-test-exercises/
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
Blood pressure
Blood pressure is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. When used without further specification, "blood pressure" usually refers to the arterial pressure of the systemic circulation. During each heartbeat, BP varies...
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.
Stress echocardiography
A stress test may be accompanied by echocardiographyEchocardiography
An echocardiogram, often referred to in the medical community as a cardiac ECHO or simply an ECHO, is a sonogram of the heart . Also known as a cardiac ultrasound, it uses standard ultrasound techniques to image two-dimensional slices of the heart...
. The echocardiography is performed both before and after the exercise so that structural differences can be compared.
Nuclear stress test
Typically, a radiotracer (Tc-99 sestamibiSestamibi
Technetium sestamibi is a pharmaceutical agent used in nuclear medicine imaging. The drug is a coordination complex of the radioisotope technetium-99m with the ligand methoxyisobutylisonitrile . The generic drug became available late September 2008...
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.
Function
- Perfusion stress test (or sestamibi) is appropriate for select patients, especially those with an abnormal resting electrocardiogram.
- Intracoronary ultrasound or angiogram can provide more information at the risk of complications associated with cardiac catheterization.
Diagnostic value
The common approach for stress testing by American College of Cardiology and American Heart Association indicates the following:- Treadmill test: sensitivity 67%, specificity 70%
- Nuclear test: sensitivity 81%, specificity 85-95%
(Sensitivity
Sensitivity and specificity
Sensitivity and specificity are statistical measures of the performance of a binary classification test, also known in statistics as classification function. Sensitivity measures the proportion of actual positives which are correctly identified as such Sensitivity and specificity are statistical...
is the percentage of sick people who are correctly identified as having the condition. Specificity
Sensitivity and specificity
Sensitivity and specificity are statistical measures of the performance of a binary classification test, also known in statistics as classification function. Sensitivity measures the proportion of actual positives which are correctly identified as such Sensitivity and specificity are statistical...
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
Atherosclerosis
Atherosclerosis is a condition in which an artery wall thickens as a result of the accumulation of fatty materials such as cholesterol...
, 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
Ischemia
In medicine, ischemia is a restriction in blood supply, generally due to factors in the blood vessels, with resultant damage or dysfunction of tissue. It may also be spelled ischaemia or ischæmia...
and lumen
Lumen (anatomy)
A lumen in biology is the inside space of a tubular structure, such as an artery or intestine...
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.
Examples of anatomical methods include:
- CT coronary calcium score
- Intima-media thickness (IMT)Intima-media thicknessIntima-media thickness , also called intimal medial thickness, is a measurement of the thickness of artery walls, usually by external ultrasound, occasionally by internal, invasive ultrasound catheters, see IVUS, to both detect the presence and to track the progression of atherosclerotic disease in...
- Intravascular ultrasound (IVUS)
Examples of physiological methods include:
- LipoproteinLipoproteinA lipoprotein is a biochemical assembly that contains both proteins and lipids water-bound to the proteins. Many enzymes, transporters, structural proteins, antigens, adhesins, and toxins are lipoproteins...
analysis - HbA1c
- Hs-CRP
- HomocysteineHomocysteineHomocysteine is a non-protein amino acid with the formula HSCH2CH2CHCO2H. It is a homologue of the amino acid cysteine, differing by an additional methylene group. It is biosynthesized from methionine by the removal of its terminal Cε methyl group...
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
Absolute contraindications to cardiac stress test include:- Acute myocardial infarction within 48 hours
- Unstable angina not yet stabilized with medical therapy
- Uncontrolled cardiac arrhythmia, which may have significant hemodynamic responses (e.g. ventricular tachycardia)
- Severe symptomatic aortic stenosis, aortic dissection, pulmonary embolism, and pericarditis
- Multivessel coronary artery diseases that have a high risk of producing an acute myocardial infarction
Adverse effects
Side effects from cardiac stress testing may include- Palpitations, chest pain, MI, shortness of breath, headache, nausea or fatigue.
- Adenosine and dipyridamole can cause mild hypotension.
- As the tracers used for this test are carcinogenic, frequent use of these tests carries a small risk of cancer.
Pharmacological agents
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
Hypertension
Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...
or left bundle branch block
Bundle branch block
A bundle branch block refers to a defect of the heart's electrical conduction system.-Anatomy and physiology:The heart's electrical activity begins in the sinoatrial node , which is situated on the upper right atrium. The impulse travels next through the left and right atria and summates at the...
. However, a exercise stress test may provide more information about exercise tolerance than a pharmacologic stress test.
Commonly used agents include:
- Vasodilators acting as adenosine receptorAdenosine receptorThe adenosine receptors are a class of purinergic receptors, G protein-coupled receptors with adenosine as endogenous ligand.-Pharmacology:...
agonists, such as Adenosine itself, and DipyridamoleDipyridamoleDipyridamole is a drug that inhibits thrombus formation when given chronically and causes vasodilation when given at high doses over a short time.-Mechanism and effects:...
(brand name "Persantine"), which acts indirectly at the receptor. - RegadenosonRegadenosonRegadenoson is an A2A adenosine receptor agonist that is a coronary vasodilator. It produces maximal hyperemia quickly and maintains it for an optimal duration that is practical for radionuclide myocardial perfusion imaging....
(brand name "Lexiscan"), which acts specifically at the Adenosine A2A receptorAdenosine A2A receptorThe adenosine A2A receptor, also known as ADORA2A, is an adenosine receptor, but also denotes the human gene encoding it.-Structure:This protein is a member of the G protein-coupled receptor family which possess seven transmembrane alpha helices...
, thus affecting the heart more than the lung. - DobutamineDobutamineDobutamine is a sympathomimetic drug used in the treatment of heart failure and cardiogenic shock. Its primary mechanism is direct stimulation of β1 receptors of the sympathetic nervous system. Dobutamine was developed by a laboratory led by Drs...
. The effects of beta-agonists such as dobutamine can be reversed by administering beta-blockers such as propranolol.
Lexiscan (Regadenoson) or Dobutamine is often used in patients with severe reactive airway disease
Reactive airway disease
Reactive airway disease is a general term for conditions involving wheezing and allergic reactions.In time it has evolved to be mistakenly used as a synonym for asthma...
(Asthma
Asthma
Asthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...
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
Aminophylline
Aminophylline is a bronchodilator. It is a compound of the bronchodilator theophylline with ethylenediamine in 2:1 ratio. The ethylenediamine improves solubility, and the aminophylline is usually found as a dihydrate-Properties:...
may be used to attenuate severe and/or persistent adverse reactions to Adenosine and Lexiscan.
Limitations
The stress test does not detect:- Atheroma
- Vulnerable plaques
The test has relatively high rates of false positives and false negatives compared with other clinical tests.
Results
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.- Increased spatial resolution allows a more sensitive detection of ischemia.
- Stress testing, even if made in time, is not able to guarantee the prevention of symptoms, fainting, or death. Stress testing, although more effective than a resting ECG at detecting heart function, is only able to detect certain cardiac properties.
- The detection of high-grade coronary artery stenosis by a cardiac stress test was the key to recognizing people who have heart attacks since 1980. From 1960 to 1990, despite the success of stress testing to identify many who were at high risk of heart attack, the inability of this test correctly identify many others is discussed in medical circles but unexplained.
- High degrees of coronary artery stenosis, which are detected by stress testing methods are often, though not always, responsible for recurrent symptoms of angina.
- Unstable atheroma produces "vulnerable plaques" hidden within the walls of coronary arteries which go undetected by this test.
- Limitation in blood flow to the left ventricle can lead to recurrent angina pectoris.
See also
CardiacCardiac arrest
Cardiac arrest
Cardiac arrest, is the cessation of normal circulation of the blood due to failure of the heart to contract effectively...
Harvard Step Test
Harvard Step Test
The Harvard Step Test is a type of cardiac stress test for detecting and/or diagnosing cardiovascular disease.It also is a good measurement of fitness, and your ability to recover after a strenuous exercise. The more quickly your heart rate returns to resting, the better shape you are in.It is a...
Metabolic equivalent
Metabolic equivalent
The metabolic equivalent of task , or simply metabolic equivalent, is a physiological concept expressing the energy cost of physical activities as multiples of resting metabolic rate and is defined as the ratio of metabolic rate during a specific physical activity to a reference rate of...
Robert A. Bruce
Robert A. Bruce
Robert Arthur Bruce was an internationally recognized cardiologist and a professor at the University of Washington...
Further reading
- Sabatine, Marc (February 15, 2000). Pocket Medicine. Lippincott Williams & Wilkins. pp. 256 pages.
- Master AM, Oppenheimer ET (1929). "A simple exercise tolerance test for circulatory efficiency with standard tables for normal individuals". Am J Med Sci . . Retrieved , retrieved on 6 August 2010.
- Gibbons, R.; Balady, G.; Timothybricker, J.; Chaitman, B.; Fletcher, G.; Froelicher, V.; Mark, D.; McCallister, B. et al. (2002). "ACC/AHA 2002 guideline update for exercise testing: summary articleA report of the American college of cardiology/American heart association task force on practice guidelines ". Journal of the American College of Cardiology , - retrieved on 6 August 2010
- E. Boden, William; Robert A. O'Rourke, Koon K. Teo, Pamela M. Hartigan, David J. Maron, M.D., William J. Kostuk, M.D., Merril Knudtson, M.D. et al. (2007). "Optimal Medical Therapy with or without PCI for Stable Coronary Disease: the COURAGE trial". New England Journal of Medicine - consulted in 12th of april 2010.
- Medline Plus ,Exercise Stress Test - Retrieved on 26 January 2010
- Harvard Health Publications,Preparation for an Exercise Stress - Retrieved on 26 January 2010
- Exercise Stress ,Cool down properly - Retrieved on 2010-01-26
- Cardiac Stress,Expect after the test - Retrieved on 2010-01-26
- Circulation, Fletcher et al. AHA Exercise Standards for Testing.
- National Guideline Clearinghouse. Cardiac Stress Test Supplement. ,2003,
- Michael Jerosch-Herold; Seethamraju, RT; Swingen, CM; Wilke, NM; Stillman, AE (2004). "Analysis of myocardial perfusion MRI". Journal of MRI.
- Thomson LE; Kim, RJ; Judd, RM ,2004, "Magnetic resonance imaging for the assessment of myocardial viability". Journal of MRI.
- A. de González (2004). "Risk of cancer from diagnostic X-rays: estimates for the UK and 14 other countries". The Lancet
- Morin; Gerber, TC; McCollough, CH ,2003, "Radiation Dose in Computed Tomography of the Heart".Circulation.
External links
- medline plus
- Harvard Health Publication
- medicine.net
- cardiacstress.net
- American journal of medical sciences
- New england journal of medicine
- Stress Test Info from the American Heart Association
- Nuclear stress test at NIH MedLine
- Stress test FAQ's
- Adenosine Nuclear Stress Test
- Dobutamine Nuclear Stress Test