What are the guidelines for electrocardiogram (ECG) interpretation in patients with and without symptoms of cardiac disease?

ECG Interpretation Guidelines

Core Principle for ECG Interpretation

All ECG interpretations must be performed by a qualified physician and cannot rely on computer algorithms alone, as computer interpretations—particularly for rhythm disturbances, ischemia, or infarction—require careful physician over-reading to avoid significant medical and legal consequences. 1

Essential Requirements for Proper ECG Interpretation

Physician Verification is Mandatory

• Computer-generated ECG interpretations are not recognized as properly interpreted ECGs and must always be verified by a qualified physician 1, 2
• Automated algorithms show poor sensitivity (30-63%) despite high specificity (95-96%) for detecting acute coronary syndromes, meaning normal automated readings cannot exclude significant coronary disease 3
• The ECG records electrical activity only; diagnoses of structural changes (myocardial infarction, hypertrophy) or pathophysiologic changes are made by inference and subject to error 1

Clinical Context is Non-Negotiable

• ECG interpretation requires integration of clinical data, comparison with previous tracings, and recognition that identical ECG patterns may occur in different structural and pathophysiologic states 1
• The same ECG pattern can be recorded in patients with vastly different underlying conditions, explaining the frequent low specificity of ECG for determining etiology and anatomy of cardiovascular disease 1

Class I Indications: ECG is First Choice and Mandatory

Symptomatic Presentations Requiring Immediate ECG

• Chest pain - may predict sudden death or myocardial infarction 1, 4, 2
• Syncope or near-syncope - to identify life-threatening arrhythmias or conduction abnormalities 1, 2
• Dizziness - may indicate arrhythmias 1, 2
• Palpitations - to diagnose rhythm disturbances 2
• Dyspnea - may signal cardiac dysfunction 4, 2
• New or worsening angina - requires immediate evaluation 1, 2
• Extreme unexplained fatigue, weakness, or prostration - may indicate cardiac disease 1, 2

Patients with Known or Suspected Cardiovascular Disease

• Any change in symptoms, signs, or laboratory findings in patients with established cardiovascular disease 1, 2
• Patients with known heart disease, peripheral vascular disease, or cerebrovascular disease undergoing intermediate- or high-risk surgery 1
• Patients with cardiovascular risk factors (coronary artery disease, heart failure, cerebrovascular disease, diabetes, renal insufficiency) undergoing vascular surgery 1

Drug Monitoring Situations

• Before and during therapy with cardioactive drugs, particularly antiarrhythmics, to evaluate QRS duration, QT interval prolongation, or proarrhythmia 2
• Serial monitoring during chemotherapy with doxorubicin or other cardiotoxic agents 2
• Patients on medications known to produce ECG changes that correlate with therapeutic responses or adverse effects 1

Post-Procedural Monitoring

• After coronary angioplasty or intracardiac procedures - ECG required just before, immediately after, and before discharge 1, 2
• After pacemaker insertion or revision - periodic ECGs throughout device lifetime to detect malfunction 1, 2
• After cardiac surgery or extensive pulmonary surgery including transplantation - serial ECGs until stable 1

Preoperative Evaluation

• All patients over 40 years undergoing any surgery 2
• All patients with known cardiovascular disease undergoing cardiac or noncardiac surgery 1, 2
• Patients older than 65 years 1
• Patients with diabetes, hypertension, chest pain, heart failure, smoking history, peripheral vascular disease, inability to exercise, or morbid obesity 1

Class III Indications: ECG is of Little or No Usefulness

• Asymptomatic patients undergoing low-risk surgery (unless medical assessment reveals high-risk features) 1
• Patients receiving therapy not known to produce ECG changes or affect conditions associated with such changes 1
• Patients with no risk factors undergoing low-risk surgery 1

Critical Diagnostic Considerations

Serial ECG Strategy

• Serial ECGs are essential when initial ECG is non-diagnostic but clinical suspicion for acute coronary syndrome remains high 4, 2
• Approximately 5% of patients with normal initial ECGs discharged from emergency departments ultimately have acute MI or unstable angina 2
• Repeat ECG is warranted when symptoms persist, change, or when initial ECG is non-diagnostic 4

Acute Coronary Syndrome Specifics

• ST-segment elevation with compatible symptoms requires emergent reperfusion therapy 4, 5
• Up-sloping ST-depression with positive T waves indicates severe left anterior descending artery obstruction 5
• Widespread ST-depression with inverted T waves and ST-elevation in aVR suggests diffuse subendocardial ischemia from severe coronary disease requiring urgent angiography if hemodynamically compromised 5

Common Pitfalls to Avoid

• Never discharge patients based solely on computer interpretation - automated readings miss 37-70% of significant coronary disease 3
• Never interpret ECG without clinical context - the responsible physician's judgment may transcend specific guideline recommendations in acute illness 1
• Never assume normal ECG excludes cardiac disease - ECG sensitivity varies by waveform and pathophysiologic condition 1
• Never rely on single ECG in suspected ACS - serial tracings dramatically improve diagnostic accuracy 4, 2

Technical Requirements for Submission

• ECG images must include all 12 leads with clear waveform visibility 4
• Include relevant clinical information: symptoms, timing, medications, and prior cardiac history 4
• For acute symptoms suggesting life-threatening conditions, in-person emergency evaluation is preferable to remote ECG image evaluation 4