How do I learn about electrocardiography (ECG)?

How to Learn ECG Interpretation

To effectively learn ECG interpretation, you must interpret at least 3,500 ECGs over 24-36 months with systematic feedback from experienced faculty, while simultaneously mastering the underlying electrophysiologic principles rather than relying solely on pattern recognition. 1

Foundation: Understanding Core Principles

Before attempting pattern recognition, you need to master the fundamental electrophysiologic concepts that generate ECG waveforms:

• Learn automaticity, conduction pathways, sinus node physiology, and atrioventricular node physiology as these form the basis for understanding all ECG abnormalities 2
• Understand that ECG leads record global electrical activity of the heart toward and away from each electrode, not just local events underneath specific electrodes—this is a critical conceptual shift from older teaching 3
• Study the physiologic mechanisms for arrhythmias and waveform generation rather than memorizing patterns alone 1

Common Pitfall: Focusing only on pattern recognition without understanding underlying mechanisms leads to misinterpretation and inability to recognize unusual presentations 2

Structured Training Requirements

Volume and Documentation

• Interpret a minimum of 3,500 ECGs documented individually over 24-36 months to achieve competency 1
• Every interpretation must be reviewed with experienced faculty who provide corrective feedback 1
• Include clinical correlation from intensive care units, emergency departments, and pacemaker clinics 1

Essential Technical Knowledge

• Master proper electrode placement and skin preparation, as errors here lead directly to misdiagnosis 2
• Understand acquisition rates, filter settings (minimum 150 Hz for adults, 250 Hz for children), and how to recognize electronic artifacts 1, 4
• Learn to accurately measure intervals in both analog and digital systems 1

Critical Warning: Inadequate high-frequency response causes systematic underestimation of signal amplitude and smoothing of diagnostic features like Q waves 5

Systematic Interpretation Framework

Apply this algorithmic approach to every ECG:

Step 1: Rate and Rhythm

• Calculate heart rate by counting large squares between R waves or counting QRS complexes in 6 seconds and multiplying by 10 (normal: 60-100 bpm) 4
• Evaluate R-R interval consistency to determine rhythm regularity 4
• Identify underlying rhythm based on P wave morphology and relationship to QRS complexes 4

Step 2: Intervals and Conduction

• Measure PR interval (normal: 120-200 ms or 3-5 small squares) to assess AV conduction 4
• Measure QRS duration (normal: <120 ms or <3 small squares) to evaluate ventricular conduction 4
• Calculate corrected QT interval (QTc: normal <450 ms for men, <460 ms for women) to assess repolarization 4

Step 3: Axis Determination

• Examine leads I and aVF to quickly determine axis quadrant (normal axis: -30° to +90°) 4
• Recognize that axis deviation serves as an independent marker of myocardial disease and chamber enlargement 4

Step 4: Waveform Morphology

• Analyze P waves (normal: upright in I, II, aVF; biphasic in V1; duration <120 ms; amplitude <2.5 mm) 4
• Examine QRS complexes for pathologic Q waves (>1 mm wide and >1/3 height of R wave suggests infarction) 4
• Assess R wave progression across precordial leads (should increase V1 to V4, then decrease toward V6) 4
• Evaluate ST segments at the J point for elevation or depression indicating ischemia 4
• Examine T wave morphology (normally upright in I, II, V3-V6; inverted in aVR) 4

Integration with Clinical Context

Never interpret ECGs in isolation from clinical data—this is a fundamental principle that prevents diagnostic errors: 1

• The same ECG pattern may occur in different structural and pathophysiologic states, explaining the low specificity for determining disease etiology 4
• Always compare with previous tracings to identify acute changes 1
• Consider age, gender (QT intervals longer in women), and medications (antiarrhythmics, psychotropics) that affect ECG parameters 4

Critical Warnings About Computer Interpretation

All computer-generated ECG interpretations must be verified by a qualified physician—unverified computer readings are not considered properly interpreted ECGs: 2, 5

• Computer algorithms provide accurate heart rate, intervals, and axes but frequently err on rhythm disturbances, ischemia, and infarction 1
• Interpretation variability exists even among expert electrocardiographers, emphasizing the need for clinical integration 5

Maintaining and Advancing Competency

Ongoing Practice Requirements

• Participate in regular continuing education through formal courses and correlative conferences 1, 2
• Seek feedback on interpretations from experienced colleagues 2
• Use case studies to enhance clinical correlation skills 2
• For those interpreting ECGs infrequently, engage in seminars or self-assessment programs to maintain currency 5

Advanced Applications

• Master recognition of STEMI equivalents including new LBBB and posterior MI patterns (ST depression V1-V4) 3
• Understand that nearly one-third of acute coronary occlusions are missed when relying solely on traditional STEMI criteria 3
• Learn to recognize hyperacute T-wave changes that precede ST elevation 3

Specific Learning Resources

• Follow published guidelines for the role of electrocardiography in clinical practice 1
• Participate in structured training periods specifically assigned for ECG interpretation 1
• Gain exposure to both full-disclosure and computer-assisted systems to understand advantages and limitations of each 1