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Several examples of the beneficial uses in diagnosis and treatment of cardiac patients are mentioned. However, keep in mind that the current list is only a brief summary and in real life the use of the ECG is broader. First, the ECG is an important tool in diagnosing and managing acute myocardial infarction. In patients with chest pain that is suspect for myocardial ischemia, the characteristic ST-segment changes (elevations or depressions) are one of the important corner stones of diagnosis and subsequent treatment. In addition, rapid resolution of the ECG changes of myocardial infarction after reperfusion therapy has prognostic value and identifies patients with reperfused coronary arteries. | Several examples of the beneficial uses in diagnosis and treatment of cardiac patients are mentioned. However, keep in mind that the current list is only a brief summary and in real life the use of the ECG is broader. First, the ECG is an important tool in diagnosing and managing acute myocardial infarction. In patients with chest pain that is suspect for myocardial ischemia, the characteristic ST-segment changes (elevations or depressions) are one of the important corner stones of diagnosis and subsequent treatment. In addition, rapid resolution of the ECG changes of myocardial infarction after reperfusion therapy has prognostic value and identifies patients with reperfused coronary arteries. | ||
In the diagnosis of the cause for severe rhythm disturbances, cardiac shock or after cardiac arrest the ECG is also of great importance for rapidly assessing possible underlying (cardiac) causes. Metabolic disturbances or medication induced arrhythmias can induce characteristic changes of the QT time, QRS and ST morphology. The diagnosis based on the ECG observations can be life-saving in emergency situations with patients in shock or after a cardiac arrest. | In the diagnosis of the cause for severe rhythm disturbances, cardiac shock or after cardiac arrest the ECG is also of great importance for rapidly assessing possible underlying (cardiac) causes. Metabolic disturbances or medication induced arrhythmias can induce characteristic changes of the QT time, QRS and ST morphology. The diagnosis based on the ECG observations can be life-saving in emergency situations with patients in shock or after a cardiac arrest. | ||
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Echocardiography is based on the use of ultrasound directed at the heart to create images of cardiac anatomy and display them in real time on a digital screen. The transthoracic echocardiography is obtained by placing a transducer in various positions on the anterior chest The processing of the ultrasound waves creates cross-sectional images of the heart and great vessels in a variety of standard planes. In general, echocardiography is a sensitive and non-invasive tool for detecting anatomic abnormalities of the heart and great vessels. | Echocardiography is based on the use of ultrasound directed at the heart to create images of cardiac anatomy and display them in real time on a digital screen. The transthoracic echocardiography is obtained by placing a transducer in various positions on the anterior chest The processing of the ultrasound waves creates cross-sectional images of the heart and great vessels in a variety of standard planes. In general, echocardiography is a sensitive and non-invasive tool for detecting anatomic abnormalities of the heart and great vessels. | ||
[[Image:Heart_lpla_echocardiography_diagram.jpg|300px|thumb|right|'''Figure 3.''' Transthoracic echocardiography. Heart normal LPLA left parasternal long axis echocardiography view.]] | |||
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The two-dimensional echocardiographic imaging technique is used to investigate the heart in multiple planes in order to asses the existence of (dys)function and structural abnormalities of cardiac chambers and valves throughout the cardiac cycle. Both the cross sectional and longitudinal views are used to look for the presence of any anatomical or functional abnormalities with most of the structures of the heart. [''Figure 4 & 5''] | The two-dimensional echocardiographic imaging technique is used to investigate the heart in multiple planes in order to asses the existence of (dys)function and structural abnormalities of cardiac chambers and valves throughout the cardiac cycle. Both the cross sectional and longitudinal views are used to look for the presence of any anatomical or functional abnormalities with most of the structures of the heart. [''Figure 4 & 5''] | ||
[[Image:Apical_4_chamber_view.gif|300px|left|thumb|'''Figure 4.''' Apical four chamber view by two dimensional echocardiography. ]] | |||
[[Image:LeftVentricleShortAxis.gif|300px|right|thumb|'''Figure 5.''' Short axis view of left ventricle by two dimensional echocardiography. ]] | |||
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In addition, in the cross sectional planes ventricular wall motion and left ventricular wall thickening during systole (an important measure of myocardial viability) can be investigated. The systematically assessment of cross sectional segment can also be used to estimate left ventricular volumes and ejection fraction. [''Figure 6''] | In addition, in the cross sectional planes ventricular wall motion and left ventricular wall thickening during systole (an important measure of myocardial viability) can be investigated. The systematically assessment of cross sectional segment can also be used to estimate left ventricular volumes and ejection fraction. [''Figure 6''] | ||
[[Image:Heart_short_axis_myocardial_segments.svg|300px|right|thumb|'''Figure 6.''' Heart short axis with myocardial segments. ]] | |||
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Although the two-dimensional imaging technique gives superior view of the important structures of the heart, the analog echocardiographic display referred to as M-mode, motion-mode, or time-motion mode, is still in use for the high resolution axial and temporal imaging. The analog technique is preferred to measure the size of structures in its axial direction, and its high sampling rate allows for the resolution of complex cardiac motion patterns. [''Figure 7''] | Although the two-dimensional imaging technique gives superior view of the important structures of the heart, the analog echocardiographic display referred to as M-mode, motion-mode, or time-motion mode, is still in use for the high resolution axial and temporal imaging. The analog technique is preferred to measure the size of structures in its axial direction, and its high sampling rate allows for the resolution of complex cardiac motion patterns. [''Figure 7''] | ||
[[Image:PLAX_Mmode.jpg|300px|right|thumb|'''Figure 7.''' Echocardiogram in the parasternal long-axis view, showing a measurement of the heart's left ventricle in M-mode. ]] | |||
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Doppler ultrasound is a technique of combined with the traditional ultrasound technique. The Doppler technique assesses changes in frequency of the reflected ultrasound compared with the transmitted ultrasound. The difference is used to be translated in a picture of the flow velocity. The continuous-wave Doppler mode is used to quantitate the exact velocity of the flow and estimate the pressure gradient when high velocities are suspected. The technique creates a graphic representation of the flow velocity in echotransducers’ beam in a time continuous wave. The technique is hampered by the fact that anatomical structures can make disturb the beam and subsequently the flow velocity measurement. When there is ambiguity about the source of the high velocity, pulsed-wave Doppler could be a more useful tool. This technique is range-gated in order to make it possible to investigate specific areas along the beam (sample volumes). Another technique widely integrated in echocardiography is the colour Doppler. The colour Doppler technique projects in coloured images informative for the direction of flow, the velocity, and the presence or absence of turbulent flow. The flow velocity colour images are in real-time combined with the two-dimensional structural imaging to investigate blood flow in the heart and great vessels. The colour Doppler image technique is in particular of use in detecting regurgitant blood flows across cardiac valves or to visualise any abnormal communications in the heart. [''Figure 8''] | Doppler ultrasound is a technique of combined with the traditional ultrasound technique. The Doppler technique assesses changes in frequency of the reflected ultrasound compared with the transmitted ultrasound. The difference is used to be translated in a picture of the flow velocity. The continuous-wave Doppler mode is used to quantitate the exact velocity of the flow and estimate the pressure gradient when high velocities are suspected. The technique creates a graphic representation of the flow velocity in echotransducers’ beam in a time continuous wave. The technique is hampered by the fact that anatomical structures can make disturb the beam and subsequently the flow velocity measurement. When there is ambiguity about the source of the high velocity, pulsed-wave Doppler could be a more useful tool. This technique is range-gated in order to make it possible to investigate specific areas along the beam (sample volumes). Another technique widely integrated in echocardiography is the colour Doppler. The colour Doppler technique projects in coloured images informative for the direction of flow, the velocity, and the presence or absence of turbulent flow. The flow velocity colour images are in real-time combined with the two-dimensional structural imaging to investigate blood flow in the heart and great vessels. The colour Doppler image technique is in particular of use in detecting regurgitant blood flows across cardiac valves or to visualise any abnormal communications in the heart. [''Figure 8''] | ||
[[Image:Ventricular_Septal_Defect.jpg|300px|right|thumb|'''Figure 8.''' Apical view with colour Doppler projection showing a ventricular septal defect. ]] | |||
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The non-invasive echocardiography has now largely replaced cardiac catheterization for calculation of the hemodynamics changes caused by valvular disease. Several examples of methods to examine hemodynamics of the heart and valves by echocardiopgraphy are: | The non-invasive echocardiography has now largely replaced cardiac catheterization for calculation of the hemodynamics changes caused by valvular disease. Several examples of methods to examine hemodynamics of the heart and valves by echocardiopgraphy are: | ||
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Unfortunately, it is impossible to obtain high-quality images or Doppler signals in as many a small percent of patients. Underlying conditions such as obesity, emphysema or chest wall deformities can limit the use of transthoracic echocardiography. A technique to partly cope with these limitations is transoesophageal echocardiography (TEE) [''Figure 9'']. | Unfortunately, it is impossible to obtain high-quality images or Doppler signals in as many a small percent of patients. Underlying conditions such as obesity, emphysema or chest wall deformities can limit the use of transthoracic echocardiography. A technique to partly cope with these limitations is transoesophageal echocardiography (TEE) [''Figure 9'']. | ||
[[Image:Transesophageal echocardiography diagram.svg|300px|thumb|'''Figure 9.''' Transoesophageal echocardiography ultrasound diagram.]] | |||
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With TEE a smaller ultrasound probe is placed on a gastroscopic device for introduction in the oesophagus behind the heart. Besides overcoming structural problems, in general TEE produces much higher resolution images of posterior cardiac structures. With TEE left atrial thrombi, small mitral valve vegetations, and thoracic aortic dissection can be diagnosed a high degree of accuracy. The downside of the techniques is the invasiveness of the procedure; the introduction of a probe into the oesophagus is very often experienced as rather uncomfortable by patients. | With TEE a smaller ultrasound probe is placed on a gastroscopic device for introduction in the oesophagus behind the heart. Besides overcoming structural problems, in general TEE produces much higher resolution images of posterior cardiac structures. With TEE left atrial thrombi, small mitral valve vegetations, and thoracic aortic dissection can be diagnosed a high degree of accuracy. The downside of the techniques is the invasiveness of the procedure; the introduction of a probe into the oesophagus is very often experienced as rather uncomfortable by patients. | ||
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==Cardiac stress test== | ==Cardiac stress test== | ||
[[Image:Stress_test.jpg|thumb|300px|'''Figure 10.''' Cardiac stress test making use of a walking treadmill. Source: Wikimedia public domain.]] | [[Image:Stress_test.jpg|thumb|300px|thumb|'''Figure 10.''' Cardiac stress test making use of a walking treadmill. Source: Wikimedia public domain.]] | ||
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). This test can be used to diagnose ischemic heart disease, and for patient prognosis after a heart attack (myocardial infarction). | |||
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 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. | ||
== | ===Indication=== | ||
[[Image:StressECG STDepression.jpg|thumb|right|300px|Stress-ECG of a patient with coronary heart disease: ST-segment depression (arrow) at 100 watts of exercise. A: at rest, B: at 75 watts, C: at 100 watts, D: at 125 watts.]] | [[Image:StressECG STDepression.jpg|thumb|right|300px|Stress-ECG of a patient with coronary heart disease: ST-segment depression (arrow) at 100 watts of exercise. A: at rest, B: at 75 watts, C: at 100 watts, D: at 125 watts.]] | ||
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 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. | ||
===Diagnostic value=== | |||
The common approach for stress testing by American College of Cardiology and American Heart Association indicates the following:<cite>Two</cite> | |||
==Diagnostic value== | |||
The common approach for stress testing by American College of Cardiology and American Heart Association indicates the following: | |||
*'''Treadmill test:''' sensitivity 73-90%, specificity 50-74% (Modified Bruce Protocol) | *'''Treadmill test:''' sensitivity 73-90%, specificity 50-74% (Modified Bruce Protocol) | ||
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(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.) | (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 | The value of stress tests has always been recognized as limited in assessing coronary atherosclerosis. This is because the stress test has a relatively high false-negative and false-positive rate. Other detection methods have higher sensitivity and specificity but this improved test characteristics often comes at a price, either in the form of radiation (CT), risk of complications in an invasive procedure (coronary angiography), or costs and limited availability (MRI). | ||
==Contraindications== | ===Contraindications=== | ||
Stress cardiac imaging is not recommended for asymptomatic, low-risk patients as part of their routine care. | Stress cardiac imaging is not recommended for asymptomatic, low-risk patients as part of their routine care.<cite>Three</cite> Some estimates show that such screening accounts for 45% of cardiac stress imaging, and evidence does not show that this results in better outcomes for patients.<cite>Three</cite> Unless high-risk markers are present, such as diabetes in patients aged over 40, peripheral arterial disease; or a risk of coronary heart disease greater than 2 percent yearly, most health societies do not recommend the test as a routine procedure.<cite>Three</cite><cite>Four</cite><cite>Five</cite><cite>Six</cite> | ||
Absolute contraindications to cardiac stress test include: | Absolute contraindications to cardiac stress test include: | ||
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*Severe symptomatic aortic stenosis, aortic dissection, pulmonary embolism, and pericarditis | *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 | *Multivessel coronary artery diseases that have a high risk of producing an acute myocardial infarction | ||
*Decompensated or inadequately controlled congestive heart failure | *Decompensated or inadequately controlled congestive heart failure<cite>Seven</cite> | ||
*Uncontrolled hypertension (blood pressure>200/110mm Hg) | *Uncontrolled hypertension (blood pressure>200/110mm Hg)<cite>Seven</cite> | ||
*Severe pulmonary hypertension | *Severe pulmonary hypertension<cite>Seven</cite> | ||
*Acute aortic dissection | *Acute aortic dissection<cite>Seven</cite> | ||
*Acutely ill for any reason | *Acutely ill for any reason<cite>Seven</cite> | ||
==Adverse effects== | ===Adverse effects=== | ||
Side effects from cardiac stress testing may include | Side effects from cardiac stress testing may include | ||
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*As the tracers used for this test are carcinogenic, frequent use of these tests carries a small risk of cancer. | *As the tracers used for this test are carcinogenic, frequent use of these tests carries a small risk of cancer. | ||
== | ===Limitations=== | ||
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The stress test does not detect: | The stress test does not detect: | ||
*Atheroma | *Atheroma | ||
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The test has relatively high rates of false positives and false negatives compared with other clinical tests. | The test has relatively high rates of false positives and false negatives compared with other clinical tests. | ||
==Results== | ===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. | 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. | ||
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*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 to correctly identify many others is discussed in medical circles but unexplained. | *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 to 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. | *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 | *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. | *Limitation in blood flow to the left ventricle can lead to recurrent angina pectoris. | ||
==Stress echocardiography== | |||
A stress test may be accompanied by echocardiography.<cite>One</cite> The echocardiography is performed both before and after the exercise so that structural differences can be compared. | |||
==Nuclear stress test== | |||
The best known example is myocardial perfusion imaging. Typically, a radiotracer (Tc-99 sestamibi, Myoview or Thallous Chloride 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 nuclear medicine technologist, a cardiology technologist, a cardiologist, and/or a nurse. | |||
==References== | ==References== | ||
<biblio> | |||
#One Rimmerman, Curtis (2009-05-05). The Cleveland Clinic Guide to Heart Attacks. Kaplan Publishing. pp. 113–. ISBN 978-1-4277-9968-5. Retrieved 25 September 2011. | |||
#Two 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 article ''A report of the American College of Cardiology / American Heart Association Task Force on Practice Guidelines'', Journal of the American College of Cardiology | |||
#Three American College of Cardiology, ''Five Things Physicians and Patients Should Question'', Choosing Wisely: an initiative of the ABIM Foundation (American College of Cardiology), retrieved August 17 2012 | |||
#Four Taylor, A. J.; Cerqueira, M.; Hodgson, J. M. .; Mark, D.; Min, J.; O'Gara, P.; Rubin, G. D.; American College of Cardiology Foundation Appropriate Use Criteria Task Force et al. (2010). ACCF/SCCT/ACR/AHA/ASE/ASNC/NASCI/SCAI/SCMR 2010 ''Appropriate Use Criteria for Cardiac Computed Tomography''. Journal of the American College of Cardiology 56 (22): 1864–1894. doi:10.1016/j.jacc.2010.07.005. PMID 21087721. edit | |||
#Five Douglas, P. S.; Garcia, M. J.; Haines, D. E.; Lai, W. W.; Manning, W. J.; Patel, A. R.; Picard, M. H.; Polk, D. M. et al. (2011). ACCF/ASE/AHA/ASNC/HFSA/HRS/SCAI/SCCM/SCCT/SCMR 2011 ''Appropriate Use Criteria for Echocardiography''. Journal of the American College of Cardiology 57 (9): 1126–1166. doi:10.1016/j.jacc.2010.11.002. PMID 21349406. edit | |||
#Six Hendel, R. C.; Abbott, B. G.; Bateman, T. M.; Blankstein, R.; Calnon, D. A.; Leppo, J. A.; Maddahi, J.; Schumaecker, M. M. et al. (2010). ''The role of radionuclide myocardial perfusion imaging for asymptomatic individuals''. Journal of Nuclear Cardiology 18 (1): 3–15. doi:10.1007/s12350-010-9320-5. PMID 21181519. edit | |||
#Seven Henzlova, Milena; Cerqueira, Hansen, Taillefer, Yao (2009). ''Stress Protocols and Tracers''. Journal of Nuclear Cardiology. doi:10.1007/s12350-009-9062-4. | |||
#Eight Weissman, Neil J.; Adelmann, Gabriel A. (2004). Cardiac imaging secrets. Elsevier Health Sciences. pp. 126–. ISBN 978-1-56053-515-7. Retrieved 25 September 2011. | |||
#Nine Nicholls, Stephen J.; Worthley, Stephen (2011-01). Cardiovascular Imaging for Clinical Practice. Jones & Bartlett Learning. pp. 198–. ISBN 978-0-7637-5622-2. Retrieved 25 September 2011. | |||
</biblio> |