ECG Interpretation Cheat sheet

 

ECG Interpretation

The electrocardiogram (ECG) is a crucial diagnostic tool for assessing the electrical activity of the heart. A thorough understanding of ECG interpretation is essential for identifying various cardiac conditions and guiding clinical decision-making.

Normal ECG

A normal ECG consists of several key components:

- P wave: represents atrial depolarization

- PR interval: time between the onset of the P wave and the QRS complex

- QRS complex: represents ventricular depolarization

- QT interval: time between the onset of the QRS complex and the end of the T wave

- T wave: represents ventricular repolarization

Heart Rate

To calculate the heart rate, count the number of R-R intervals in 6 seconds and multiply by 10. A normal heart rate is between 60-100 beats per minute.

Rhythm

Assess the rhythm by evaluating the P-P interval and R-R interval. A regular rhythm has a consistent P-P and R-R interval.

P Wave

Evaluate the P wave for morphology, duration, and axis. Abnormalities can indicate atrial enlargement or ectopic atrial rhythms.

PR Interval

Measure the PR interval from the onset of the P wave to the onset of the QRS complex. A prolonged PR interval (>200 ms) can indicate first-degree AV block.

QRS Complex

Assess the QRS complex for duration, morphology, and axis. Abnormalities can indicate ventricular hypertrophy, bundle branch block, or ventricular arrhythmias.

QT Interval

Measure the QT interval from the onset of the QRS complex to the end of the T wave. A prolonged QT interval can increase the risk of torsades de pointes.

T Wave

Evaluate the T wave for morphology and axis. Abnormalities can indicate ischemia, ventricular hypertrophy, or electrolyte imbalances.

ECG Interpretation Approach

When interpreting an ECG, follow a systematic approach:

1. Assess the heart rate and rhythm

2. Evaluate the P wave, PR interval, QRS complex, QT interval, and T wave

3. Look for signs of ischemia, infarction, or arrhythmias

4. Consider the clinical context and patient history

Common ECG Abnormalities

- Atrial fibrillation: irregularly irregular rhythm with absent P waves

- Ventricular tachycardia: wide QRS complex tachycardia

- Bundle branch block: widened QRS complex with abnormal morphology

- Myocardial infarction: Q waves, ST-segment elevation, or T-wave inversion

Clinical Application

ECG interpretation is crucial in various clinical settings, including:

- Emergency medicine: diagnosing acute coronary syndromes, arrhythmias, or cardiac arrest

- Cardiology: evaluating cardiac structure and function, diagnosing cardiomyopathies or channelopathies

- Primary care: monitoring patients with cardiovascular disease, detecting asymptomatic arrhythmias or ischemia

In conclusion, ECG interpretation requires a systematic approach and a thorough understanding of cardiac electrophysiology. By analyzing the various components of the ECG and considering the clinical context, healthcare professionals can diagnose and manage a wide range of cardiac conditions.

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