How do you interpret an electrocardiogram (ECG)?

From the Guidelines

To interpret an ECG, follow a systematic approach focusing on key components, including heart rate, rhythm, P waves, PR interval, QRS complex, ST segment, T wave morphology, and QT interval, as outlined in the American Heart Association's scientific statement from 2007 1. When interpreting an ECG, it is essential to consider the clinical context, as noncardiologists may be more influenced by patient history than cardiologists, and computers can decrease the time needed to interpret ECGs but should only be relied on as an adjunct tool for a trained provider 2.

Key Components of ECG Interpretation

• Heart rate: normally between 60-100 beats per minute
• Rhythm: evaluate for regularity and identify P waves, which represent atrial depolarization
• PR interval: normally 0.12-0.20 seconds
• QRS complex: normally less than 0.12 seconds wide
• ST segment: examine for any elevation or depression, which could indicate ischemia or infarction
• T wave morphology: assess for any abnormalities
• QT interval: normally less than 450 ms in men, 470 ms in women ### Importance of Clinical Context and Training
• Clinical context is crucial for accurate interpretation, as normal variations exist and patient history can influence interpretation 2
• Practice regularly with various ECGs to improve skills, and when in doubt, consult with a more experienced colleague or cardiologist
• Residency training in internal medicine with Advanced Cardiac Life Support instruction should continue to be sufficient for bedside interpretation of resting 12-lead ECGs in routine and emergency situations, according to the American College of Physicians 2

From the Research

Interpreting an Electrocardiogram (ECG)

To interpret an ECG, one must follow a systematic approach that includes:

• Identifying the heart rate and rhythm
• Determining the axis of the heart
• Recognizing any abnormalities, such as ischemia, arrhythmias, or conduction disorders
• Synthesizing the findings into a succinct and accurate interpretation 3

Key Components of ECG Interpretation

The key components of ECG interpretation include:

• Recognizing normal and abnormal P waves, QRS intervals, ST elevations, and QT intervals
• Identifying dysrhythmias that can lead to sudden cardiac death
• Understanding the clinical presentation and specific ECG findings associated with sudden cardiac death syndromes 3
• Being able to identify cardiac ischemia, atrioventricular blocks, and bundle branch blocks 3, 4

Challenges in ECG Interpretation

Studies have shown that medical graduates and healthcare professionals may not be proficient in ECG interpretation, with difficulties in:

• Accurately determining heart rate and rhythm 5
• Identifying and interpreting important common or life-threatening abnormalities, such as atrial fibrillation, second-degree heart block, and ventricular pacing 5, 6
• Recognizing subtle ECG findings that could herald sudden death 3

Improving ECG Interpretation Skills

To improve ECG interpretation skills, online learning modules and educational resources can be effective, offering:

• A self-paced and accessible way to learn and practice ECG interpretation
• Opportunities for real-time retrieval practice, feedback, and repetition
• A concise and effective supplemental tool that can be incorporated into residency program curricula 3, 7