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ECG - short PR interval
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📖 About
- 👉 A short PR interval is defined as PR < 0.12 seconds (120 ms) on ECG.
- It reflects either:
- 💡 Faster conduction from atria → ventricles (via an accessory pathway), or
- 💡 An ectopic atrial or junctional pacemaker closer to the AV node.
- Clinical importance: may be associated with pre-excitation syndromes and risk of tachyarrhythmias.
🩺 Causes
- ⚡ Wolff–Parkinson–White (WPW) Syndrome – short PR with a characteristic delta wave (slurred upstroke of QRS), due to an accessory pathway (Bundle of Kent).
- ⚡ Lown–Ganong–Levine (LGL) Syndrome – very short PR but with normal/narrow QRS (James fibre bypassing AV node).
- ⚡ Ventricular ectopic beat occurring immediately after the P wave.
- ⚡ Low atrial rhythm – P waves arise closer to the AV node, shortening conduction time.
- ⚡ Coronary sinus escape rhythm – impulses originate low in the atrium near the AV junction.
🔎 Clinical Significance
- Short PR + delta wave → think WPW (risk of AVRT, atrial fibrillation with rapid conduction).
- Short PR without delta → think LGL or junctional/low atrial rhythm.
- Important in differentiating benign short PR vs pre-excitation that carries arrhythmia risk.
🖼️ ECG Example
💡 Exam tip: Always check if the short PR is accompanied by a delta wave → this immediately points to WPW syndrome.
| The content on this website is provided for educational and informational purposes only to support exam preparation (e.g., MLA, MRCP, USMLE) and learning. This is NOT medical advice, diagnosis, treatment, or professional guidance. It does not replace consultation with a qualified healthcare professional, official guidelines (e.g., NICE, GMC, BNF), or supervised clinical practice. Always verify information with current, authoritative sources. Makindo and its contributors accept no liability for any reliance on this content, including errors, omissions, or any resulting harm, loss, or consequences. By using this site, you agree to these terms. |
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