Can you interpret an electrocardiogram (ECG) image?

ECG Interpretation Capability and Requirements

I cannot interpret an ECG image directly, but I can guide you through the systematic approach required for accurate interpretation, which must always be performed by a qualified physician.

Why Physician Interpretation is Mandatory

Computer-based ECG interpretation—including AI systems—must never replace physician review for clinical decision-making. 1 The American College of Physicians explicitly states that computer analyses are useful adjuncts only, and errors in automated interpretation remain common, with accuracy rates ranging from 0% to 94% for certain diagnoses, particularly arrhythmias. 1

• All computer-generated ECG reports require mandatory physician over-reading before any clinical decisions are made. 1, 2
• The same ECG pattern can occur in different structural and pathophysiologic states, making context-dependent physician interpretation essential. 3, 4
• Computer programs correctly classify only 69.8-91.3% of ECGs compared to 96.0% for expert cardiologists. 1

Systematic Approach to ECG Interpretation

When a qualified physician interprets an ECG, they should follow this algorithmic framework:

Step 1: Verify Technical Quality

• Confirm proper electrode placement, particularly precordial leads, as misplacement significantly alters interpretation and causes false diagnoses. 4, 5
• Ensure minimum high-frequency response of 150 Hz for adults (250 Hz for children) to maintain diagnostic precision. 4, 5
• Check for artifacts, electrical interference, and baseline stability before proceeding. 4

Step 2: Calculate Rate and Identify Rhythm

• Count QRS complexes in a 6-second strip and multiply by 10, or use 300 divided by the number of large boxes between R waves. 3, 4, 5
• Confirm sinus rhythm by identifying a P wave before each QRS complex with consistent PR interval (normal: 60-100 bpm). 3, 4
• Note any irregularities: premature beats, pauses, or completely irregular patterns suggesting atrial fibrillation. 4, 5

Step 3: Measure Critical Intervals

• PR interval: Normal 120-200 ms (3-5 small squares) to assess AV conduction. 3, 5
• QRS duration: Normal <120 ms (<3 small squares) to identify ventricular conduction delays. 3, 5
• QTc interval: Calculate using Bazett's formula; normal <450 ms for men, <460 ms for women. 3, 5

Step 4: Determine Electrical Axis

• Examine leads I and aVF: normal axis when both positive (+90° to -30°). 3, 4, 5
• Left axis deviation: lead I positive, aVF negative (-30° to -90°). 3, 4
• Right axis deviation: lead I negative, aVF positive (+90° to +180°). 3, 4

Step 5: Analyze Waveform Morphology

• P waves: Normal morphology is upright in I, II, aVF; biphasic in V1; duration <120 ms, amplitude <2.5 mm. 3
• QRS complexes: Look for pathologic Q waves (>1 mm wide and >1/3 height of R wave) suggesting myocardial infarction. 3, 4
• ST segments: Measure at J point for elevation (>0.1 mV in limb leads or >0.15-0.2 mV in precordial leads) indicating acute injury requiring emergent reperfusion. 3, 4, 5
• T waves: Assess for inversion, hyperacute changes, or flattening. 3, 5

Step 6: Integrate Clinical Context

• Never interpret the ECG in isolation—the same finding has different implications depending on presenting symptoms. 4, 5, 2
• Consider patient history including coronary artery disease, cardiomyopathy, hypertension, or diabetes. 4
• Compare with previous ECGs when available to identify dynamic changes. 4, 5

Critical Pitfalls to Avoid

• Do not accept computer interpretation without verification—automated systems produce frequent errors that can lead to adverse patient outcomes. 1, 4, 5
• Do not overlook age-specific variants: T-wave inversions in V1-V3 are normal in children; sinus bradycardia to 30 bpm can be physiologic in athletes. 4
• Do not miss lead reversal or muscle artifacts—these recording errors cause computer misinterpretation. 2
• Noncardiologists are more influenced by clinical history than cardiologists when interpreting ECGs, making systematic approach even more critical. 1, 5

Competency Requirements

• Successful completion of internal medicine residency, board certification, and Advanced Cardiac Life Support training demonstrates basic competency for bedside ECG interpretation in routine and emergency settings. 1, 5
• Continuing medical education through seminars or self-assessment programs is essential for physicians who read ECGs infrequently. 4, 5
• First-year residents demonstrate only 50% accuracy in ECG interpretation, emphasizing the need for structured training. 6

Emergency Department Considerations

• Obtain the 12-lead ECG immediately in patients with chest pain, syncope, or symptoms predictive of sudden death or myocardial infarction (sensitivity 76%, specificity 88% for acute cardiac ischemia). 5
• Paramedics and nurses can identify STEMI independently with mandatory initial training and ongoing medical oversight, allowing earlier catheterization lab activation. 5
• Field-transmitted ECG for expert interpretation is reasonable if on-site interpretation is unavailable. 5