How do I learn to read electrocardiograms (EKGs)?

How to Learn EKG Interpretation

To learn EKG interpretation effectively, you should interpret a minimum of 3,500 ECGs over 24-36 months under supervision with faculty review of each interpretation, as this represents the evidence-based standard for achieving Level 2 competency in electrocardiography. 1

Structured Training Approach

Volume and Supervision Requirements

• Interpret 3,500 ECGs over 24-36 months with documentation of each interpretation individually, which can be accomplished through dedicated training periods or continuous experience 1
• Review all interpretations with experienced faculty who are knowledgeable in clinical correlations and ECG patterns 1
• For physicians requiring basic competency (non-cardiologists), the American College of Physicians suggests that residency training in internal medicine with Advanced Cardiac Life Support instruction is sufficient for bedside interpretation in routine and emergency situations 1
• Alternative minimum standards suggest interpreting 500 ECGs under supervision for initial competency, though this represents a lower threshold 1

Clinical Integration Strategy

• Gain experience in intensive care units, emergency rooms, and pacemaker/defibrillation clinics to integrate ECG findings with clinical problems 1
• Always interpret ECGs in the context of the patient's clinical presentation, as the same finding may have different implications depending on symptoms 2, 3
• Recognize that noncardiologists are more influenced by patient history in interpreting ECGs than cardiologists, making clinical context particularly important for your interpretations 1, 4

Systematic Interpretation Framework

Step 1: Technical Quality Assessment

• Evaluate recording quality before interpretation by checking for artifacts, electrical interference, and baseline stability 2
• Verify proper electrode placement, appropriate bandwidth settings (minimum 150 Hz for adults, 250 Hz for children), and signal quality 2, 3
• Check for electrode misplacement, particularly precordial leads, which can significantly alter interpretation and lead to false diagnoses 2, 5

Step 2: Rate and Rhythm Analysis

• Calculate heart rate by counting QRS complexes in a 6-second strip and multiplying by 10, or use the formula 300 divided by the number of large boxes between consecutive R waves 2, 3
• Identify the underlying rhythm by examining P wave morphology and relationship to QRS complexes (sinus, atrial, junctional, ventricular) 2, 3
• Evaluate rhythm regularity by examining R-R intervals for consistency 3
• Note any irregularities such as premature beats, pauses, or completely irregular patterns that might suggest atrial fibrillation 2

Step 3: Intervals and Conduction

• Measure PR interval (normal: 120-200 ms or 3-5 small squares) to assess AV conduction 2, 3
• Evaluate QRS duration (normal: <120 ms or <3 small squares) to identify ventricular conduction delays 2, 3
• Calculate QT interval corrected for heart rate (QTc) using Bazett's formula, with normal values <450 ms for men and <460 ms for women 2, 3
• Identify any conduction abnormalities such as AV blocks, bundle branch blocks, or pre-excitation 2, 3

Step 4: Axis Determination

• Examine leads I and aVF to quickly determine the quadrant of the axis 2, 3
• Normal axis: +90° to -30° (positive in both leads I and aVF) 2, 3
• Left axis deviation: -30° to -90° (positive in lead I, negative in aVF) 2, 3
• Right axis deviation: +90° to +180° (negative in lead I, positive in aVF) 2, 3
• Extreme axis deviation: +180° to -90° (negative in both leads I and aVF) 2

Step 5: Waveform Morphology Analysis

• Examine P wave morphology (normal: upright in I, II, aVF; biphasic in V1; duration <120 ms; amplitude <2.5 mm) to assess atrial conduction 3
• Analyze QRS complex morphology for pathologic Q waves (>0.04 seconds or >25% of R wave amplitude) suggesting myocardial infarction 2, 3
• Assess R wave progression across precordial leads, with R wave amplitude increasing from V1 to V4 and then decreasing toward V6 3
• Look for voltage criteria for ventricular hypertrophy: left ventricular hypertrophy using Sokolow-Lyon criterion (S in V1 + R in V5 or V6 >3.5 mV) 2, 3

Step 6: ST Segments and T Waves

• Examine ST segments for elevation (>0.1 mV in limb leads or >0.15-0.2 mV in precordial leads) or depression that may indicate acute injury or ischemia 2, 3
• Assess T wave morphology (normally upright in leads I, II, V3-V6; inverted in aVR; variable in III, aVL, aVF, V1, and V2) 3
• Look for T-wave abnormalities including inversion, hyperacute changes, or flattening 2
• Note the location of abnormalities to determine the affected coronary territory 2

Essential Knowledge Base

Physiological Understanding

• Understand the physiologic mechanisms for arrhythmias and electrocardiographic waveforms rather than simply recognizing patterns 1, 6
• Learn general electrophysiological concepts including automaticity, conduction, sinus node physiology, and atrioventricular node physiology 4, 6
• Understand the hemodynamic effects of arrhythmias and appropriate clinical responses 4

Technical Competencies

• Understand the instrumentation necessary to acquire, process, and store ECGs in both analog and digital format 1
• Recognize the effect of acquisition rates and filter settings, as well as electronic artifacts 1, 7
• Be able to accurately measure basic ECG intervals in both analog and digital systems 1
• Understand that inadequate high-frequency response results in systematic underestimation of signal amplitude and smoothing of important features like Q waves 2

Critical Pitfalls to Avoid

Computer Interpretation Errors

• Never accept computer interpretation without physician verification—automated systems still produce frequent errors and are not recognized as properly interpreted ECGs without qualified physician review 2, 3, 4
• Use computer interpretations only as helpful adjuncts, not substitutes for physician interpretation in clinical decision making 2, 4
• Recognize that computers may decrease interpretation time and can reduce some errors, but they have shown less accuracy than physician interpreters 1

Technical and Interpretive Errors

• Avoid misplacement of electrodes, particularly precordial leads, which can significantly alter interpretation and lead to false diagnoses 2, 5
• Do not use inadequate filtering settings, which can distort waveforms and affect measurements 2, 7
• Avoid interpreting ECG findings in isolation without considering clinical context, which may lead to inappropriate management decisions 2, 8
• Always compare with previous ECGs when available to avoid missing important changes 2

Pattern Recognition Limitations

• Do not focus only on pattern recognition without understanding underlying physiological mechanisms, as this can lead to misinterpretation 4, 6
• Recognize that interpretation of ECGs varies greatly, even among expert electrocardiographers, underscoring the need for ongoing education 2
• Understand that diagnoses of structural or pathophysiologic changes are made by inference and therefore subject to error 2, 3

Maintaining Competency

Ongoing Practice Requirements

• Read 100 ECGs yearly to maintain competency after achieving initial proficiency 1
• Participate in regular continuing education through seminars or self-assessment programs, especially if you read ECGs infrequently 2, 4
• Seek feedback on interpretations from experienced colleagues for ongoing development 4

Educational Resources

• Attend formal courses and correlative conferences in electrocardiography 1
• Use case studies to enhance clinical correlation skills 4
• Review guidelines for the role of electrocardiography in clinical practice 1

Special Considerations

Population-Specific Factors

• Consider age-specific variations: in neonates, normal axis ranges 55-200° at birth, decreasing to ≤160° by 1 month; T waves are often inverted in leads V1, V2, and V3 in children older than 1 month 2, 3
• Recognize that QRS voltage criteria decline with age and vary by population 3
• Account for gender differences: QT intervals are typically longer in women, with normal QTc <460 ms for women versus <450 ms for men 2, 3
• Consider normal variants in athletes, such as sinus bradycardia (≥30 beats/min) 2

Medication and Clinical Context

• Recognize that certain medications can affect ECG findings, including antiarrhythmics and psychotropics 3
• Always integrate ECG interpretation with the patient's clinical presentation, as the same ECG pattern may occur in different structural and pathophysiologic states 2, 3