In an ECG (Electrocardiogram), the PR interval represents the time it takes for the electrical impulse to travel from the atria to the ventricles, initiating ventricular depolarization.
Detailed Explanation of the PR Interval
The PR interval is a crucial measurement in ECG interpretation. It reflects the conduction time from the beginning of atrial depolarization (P wave) to the beginning of ventricular depolarization (QRS complex).
Normal PR Interval
- The normal PR interval duration is 0.12-0.20 seconds (120-200 milliseconds). This range indicates that the electrical impulse is traveling through the AV node and His-Purkinje system within an expected timeframe.
Clinical Significance
Variations in the PR interval duration can indicate underlying heart conditions:
- Prolonged PR Interval (First-Degree AV Block): A PR interval longer than 0.20 seconds suggests a delay in the AV node's conduction of the electrical impulse.
- Shortened PR Interval: A PR interval shorter than 0.12 seconds may indicate pre-excitation syndromes like Wolff-Parkinson-White (WPW) syndrome, where an abnormal accessory pathway bypasses the AV node, leading to early ventricular activation.
Summary
| Feature | Description |
|---|---|
| Definition | Time from the start of the P wave to the start of the QRS complex. |
| Normal Range | 0.12-0.20 seconds (120-200 milliseconds). |
| Prolonged PR | May indicate First-Degree AV Block, suggesting a delay in AV node conduction. |
| Shortened PR | May indicate pre-excitation syndromes like Wolff-Parkinson-White (WPW), suggesting early ventricular activation. |
Understanding the PR interval and its variations is essential for accurate ECG interpretation and diagnosis of cardiac conditions.
