Chronic stable angina exercise electrocardiography
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In patients with chronic stable angina, exercise ECG is more sensitive and specific to identify inducible ischemia and to diagnose coronary artery disease. ECG abnormalities associated with MI include: down sloping of ST-segment depression or elevation, accompanying angina that occurs at a low workload during early stages of exercise and persistent for more than 3-minutes after exercise. The reliability of diagnosis is shown to improve with the evaluation of ST changes in relation to heart rate. Bruce protocol or treadmill (expressed in terms of METs) or bicycle ergometer (expressed in terms of watts) are used to detect MI. Exercise ECG test must be terminated on the achievement of maximal predicted heart rate and/or if the patient becomes symptomatic or develops pain with significant ST-segment changes. Exercise ECG test also provides prognostic stratification to evaluate the response to medical therapy or revascularization.
ST-segment changes suggestive of coronary artery disease include:
- Down sloping or horizontal ST segment depressions are highly suggestive of myocardial ischemia, particularly when:
- It occurs at a low workload,
- It occurs during early stages of exercise,
- It persists for more than 3 minutes after exercise, or
- It is accompanied by chest discomfort that is compatible with angina.
Sensitivity and Specificity
- Exercise electrocardiography has a sensitivity of approximately 70% for detecting coronary artery disease.
- Exercise electrocardiography has a specificity of approximately 75% for excluding coronary artery disease.
- To assess the probability of coronary artery disease in an individual patient, the exercise ECG result must be integrated with the clinical presentation.
- Conditions that increase the probability of exercise ECG yielding false positive results are:
- An abnormal resting ECG associated with left ventricular hypertrophy, intraventricular conduction abnormalities, pre-excitation syndromes (Long Ganong Lewine Syndrome = LGL, Wolf-Parkinson-White syndrome = WPW and Mahaim type), electrolyte imbalance or therapy with digitalis
- In women, the lower prior probability of CAD is associated with more false positive results on ECG.
- On the other hand, a fall in systolic pressure of 10 mm Hg or more during exercise or the appearance of a murmur of mitral regurgitation during exercise increases the probability that, an abnormal stress ECG is a true positive test result.
Treadmill Exercise Test
- Treadmill exercise test is more preferable to bicycle exercise test (or ergometer) for detecting myocardial ischemia.
- In patients who cannot perform treadmill exercise, pharmacologic stress scintigraphy or echocardiography is preferable to upper body arm exercise.
- Variables of the Treadmill Exercise Test which indicate the high risk are:
- Short exercise duration less than 5 METs,
- Significant ST segment depression (magnitude ≥2 mm, starts at exercise stage I or II, duration of exercise test is <5 minutes and ≥5 leads with ST changes,
- Significant changes in blood pressure: low peak systolic blood pressure (<130 mm Hg), significant decrease in systolic blood pressure during the test (below the resting standing blood pressure),
- Inability to attain to the target heart rate,
- Presence of exercise induced angina,
- Presence of frequent ventricular ectopy (e.g. couplets or tachycardia) at low workload.
For more information on exercise EKG during exercise stress testing, click here.
ACC/AHA/ACP–ASIM Guidelines for the Management of Patients With Chronic Stable Angina (DO NOT EDIT)
Stress Testing and Advanced Imaging for Initial Diagnosis in Patients With Suspected SIHD Who Require Noninvasive Testing(DO NOT EDIT)
Patients able to exercise
|"1. Standard exercise ECG testing is recommended for patients with an intermediate pretest probability of IHD who have an interpretable ECG and at least moderate physical functioning or no disabling comorbidity(Level of Evidence: A)"|
|"1. For patients with a low pretest probability of obstructive IHD who do require testing, standard exercise ECG testing can be useful, provided the patient has an interpretable ECG and at least moderate physical functioning or no disabling comorbidity. (Level of Evidence: C)"|
Patients unable to exercise
|"1. Standard exercise ECG testing is not recommended for patients who have an uninterpretable ECG or are incapable of at least moderate physical functioning or have disabling comorbidity. (Level of Evidence: C)"|
ESC Guidelines- Exercise ECG for Initial Diagnostic Assessment of Angina (DO NOT EDIT)
|"1. Patients with symptoms of angina and intermediate pre-test probability of coronary artery disease based on age, gender, and symptoms, unless unable to exercise or displays ECG changes which make ECG non-evaluable. (Level of Evidence: B)"|
|"1. Patients with more than 1 mm ST-depression on resting ECG or taking digoxin. (Level of Evidence: B)"|
|"1. In patients with low pre-test probability (less than 10% probability) of coronary disease based on age, gender, and symptoms. (Level of Evidence: B)"|
ESC Guidelines- Exercise ECG for Routine Re-assessment in Patients with Chronic Stable Angina (DO NOT EDIT)
|"1. Routine periodic exercise ECG in the absence of clinical change. (Level of Evidence: C)"|
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- Elamin MS, Boyle R, Kardash MM, Smith DR, Stoker JB, Whitaker W et al. (1982) Accurate detection of coronary heart disease by new exercise test. Br Heart J 48 (4):311-20. PMID: 6127094
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