ECG Findings and Risk Stratification in Unstable Angina

ECG Changes and Diagnostic Considerations

• Approximately 5% of patients with unstable angina may have a completely normal EKG even during symptoms, according to the European Society of Cardiology 1, 2
• ST-segment depression (≥0.5 mm) in two or more contiguous leads is highly suggestive of unstable angina in the appropriate clinical context, as recommended by the European Society of Cardiology 1
• T-wave inversion (≥1 mm) in leads with predominant R waves is also indicative of unstable angina, though less specific than ST-segment depression, as noted by the European Society of Cardiology 1
• Deep symmetrical T-wave inversion in anterior chest leads often indicates significant proximal left anterior descending coronary artery stenosis, according to the European Society of Cardiology 1
• Transient episodes of bundle branch block may occasionally occur during ischemic attacks, as reported by the European Society of Cardiology 1
• Several studies have shown that around 5% of patients with normal ECGs who were discharged from emergency departments were ultimately found to have either acute myocardial infarction or unstable angina, as found by the European Society of Cardiology 1
• Non-specific ST-segment and T-wave changes (<1 mm) may be present but are less reliable indicators, according to the European Society of Cardiology 1
• A completely normal ECG recorded during an episode of significant chest pain should prompt consideration of other possible causes for the patient's complaints, but does not exclude unstable angina, as stated by the European Society of Cardiology 1, 2

Risk Stratification

• Angina at rest with transient ST-segment changes greater than 0.5 mm is a high-risk feature, as identified by the American Heart Association 3
• Bundle-branch block, new or presumed new, is a high-risk feature, according to the American Heart Association 3
• Sustained ventricular tachycardia is a high-risk feature, as reported by the American Heart Association 3
• T-wave changes are an intermediate-risk feature, according to the American Heart Association 3
• Pathological Q waves or resting ST-depression less than 1 mm in multiple lead groups are intermediate-risk features, as noted by the American Heart Association 3
• Normal or unchanged ECG during episodes of chest pain is a low-risk feature, according to the American Heart Association 3

Clinical Implications and Recommendations

• When unstable angina is suspected but the initial ECG is not diagnostic, serial ECGs should be performed at 15-30 minute intervals to detect potential development of ST-segment changes, as recommended by the American Heart Association 4
• Ideally, an ECG should be obtained when the patient is symptomatic and compared with a tracing obtained when symptoms have resolved, according to the European Society of Cardiology 1
• Comparison with previous ECGs, if available, is extremely valuable, particularly in patients with co-existing cardiac pathology, as stated by the European Society of Cardiology 1
• Certain patient populations, such as the elderly, diabetics, and women, are more likely to present with atypical symptoms and non-diagnostic ECGs, as noted by the European Society of Cardiology, rather than Praxis Medical Insights 5
• The distinction between unstable angina and NSTEMI is ultimately based on the detection of markers of myocardial necrosis in the blood, not solely on ECG findings, according to the European Society of Cardiology, rather than Praxis Medical Insights 5
• A normal ECG during chest pain does not rule out unstable angina and should not provide false reassurance if clinical suspicion remains high, as stated by the European Society of Cardiology 1, 2