Altering the diagnostic criteria varied sensitivity between 45% and 69% but reduced specificity from 98% to 81%. An ST/junctional ST elevation of ≥0.2 mV in more than one anterior lead has a sensitivity of 56% and a specificity of 94% for acute myocardial infarction defined by clinical history and biochemical evidence. The exact degree of ST elevation required for a diagnosis of an evolving acute myocardial infarction can influence the sensitivity of the ECG. In a group of patients with known coronary artery disease, exercise electrocardiography had a sensitivity of only 53% for identifying those persons who would prove to have an acute coronary event within the next 2.5 years. Technetium-99m isonitrile single-photon emission computed tomography–based dobutamine stress testing has been reported to be able to identify patients with coronary artery disease accurately 64% of the time. 7 The specificity of the ETT was based on “true positives” or patients with significant stenosis on an angiogram. 6 These data have been used to develop the American College of Cardiology/American Heart Association Guidelines for Exercise Testing. 5 For this reason, troponin levels are obtained to correlate with serial ECG tracings.Ī large meta-analysis of more than 132 studies with 24,074 patients found the overall sensitivity of an exercise tolerance test (ETT) to be 68% with a specificity of 77%. One study reported that patients presenting with a history suggestive of ischemic cardiac pain but with a normal ECG still have an incidence of myocardial infarction of 7%. 1-3 The presence of an ST elevation or Q waves can be used to accurately delineate an infarct with a specificity of between 91% and 98% due to variations in coronary anatomy and technique of ECG testing, however, it is more difficult to determine the actual artery involved. Studies report that ECGs can successfully identify patients with proven stenosis on angiography in 36% to 87% of cases. While it is possible that this patient had misunderstood what was being told to her or that her physician chose not to “worry” her since she had reported no clinical issues, I decided to use this case as an opportunity to review with you the literature regarding the sensitivity and specificity of ECGs and what Q waves may actually signify. When I questioned her further about whether she had had a recent ECG, she reported that she, in fact, had one recently and was told by her physician that, although it showed abnormal findings, “electrocardiograms were unreliable and I had not had a heart attack despite it possibly showing one on the tracing.” Although she had evidence of an anterolateral myocardial infarction, age undetermined, on her ECG tracing, she told me she had been recently informed by her primary care physician that her heart was healthy and that she did not have any problems. ![]() I recently saw an older woman in the hospital with significant abnormalities on her electrocardiogram (ECG).
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