How to interpret an Electrocardiogram (EKG)?

From the Guidelines

To interpret an EKG, a systematic approach is crucial, starting with examining the rate, rhythm, and intervals, and then evaluating the morphology of the P, QRS, and T waves, as well as checking for any additional waves, as recommended by the American Heart Association and the American College of Cardiology 1. When interpreting an EKG, it's essential to follow a step-by-step approach to ensure accuracy and completeness.

• First, examine the rate by counting the number of QRS complexes in a 6-second strip and multiplying by 10, with normal being 60-100 beats per minute.
• Next, assess rhythm by checking if P waves precede each QRS complex and if intervals are consistent.
• Evaluate the P wave morphology for atrial activity, then measure the PR interval (normal: 0.12-0.20 seconds) to assess AV conduction.
• Examine QRS complex width (normal: less than 0.12 seconds) and morphology for ventricular depolarization abnormalities.
• Check the ST segment for elevation or depression, which may indicate ischemia, injury, or infarction.
• Analyze the T wave for abnormal inversions or elevations suggesting repolarization issues.
• Finally, calculate the QT interval (normal: less than half the preceding RR interval) and check for any additional waves like U waves or delta waves. With practice, you'll develop pattern recognition for common abnormalities like atrial fibrillation, heart blocks, bundle branch blocks, and myocardial infarction patterns, as outlined in the recommendations from the American College of Physicians 1. It's also important to note that computer interpretation of ECGs can be a useful adjunct to physician interpretation, but should not replace a qualified physician in making patient management decisions, as errors in computer interpretation are still common 1. Additionally, training in ECG interpretation during residency should provide physicians with knowledge of the pathophysiology of electrocardiographic abnormalities, and the opportunity to apply this knowledge in bedside clinical decision making, as recommended by the American College of Physicians 1.

From the Research

Interpreting an Electrocardiogram (EKG)

To interpret an EKG, one must consider several key factors, including:

• The presence of P waves, QRS complexes, and T waves, and their relationships to one another 2
• The morphology of these waves, including their amplitude, duration, and shape 3, 2
• The presence of any abnormalities, such as ST segment elevation or depression, Q waves, or arrhythmias 3, 4

Identifying Key Components

The key components of an EKG include:

• P waves, which represent atrial depolarization 2
• QRS complexes, which represent ventricular depolarization 2
• T waves, which represent ventricular repolarization 2
• The PR interval, which represents the time between atrial and ventricular depolarization 2
• The QT interval, which represents the time between ventricular depolarization and repolarization 2

Analyzing Wave Morphology

The morphology of the P, QRS, and T waves can provide important information about the heart's electrical activity, including:

• The presence of a Brugada pattern, which is characterized by a positive terminal deflection and ST segment elevation in the right precordial leads 3
• The presence of bundle branch blocks or fascicular blocks, which can affect the morphology of the QRS complex 2
• The presence of ischemia or infarction, which can affect the morphology of the ST segment and T wave 4

Using Online Learning Modules

Online learning modules can be an effective way to improve EKG interpretation skills, particularly for emergency medicine residents 4. These modules can provide:

• Interactive lessons and quizzes to help learners develop their skills
• Access to a large database of EKG examples, including normal and abnormal tracings
• The ability to practice interpreting EKGs at one's own pace, with immediate feedback and assessment

Detecting QRS Complexes and P Waves

Detecting QRS complexes and P waves is a critical step in EKG interpretation, and can be accomplished using a variety of methods, including:

• Complete ensemble empirical mode decomposition with adaptive noise 5
• Conventional filtering techniques 5
• Novel methods that reconstruct signals for QRS and P wave detection 5