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Sinus arrhythmia
💓 Sinus arrhythmia is a benign, physiological variation of normal sinus rhythm, most commonly observed in children, adolescents, and healthy young adults. It reflects the natural influence of respiration on vagal tone.
📖 About
- Represents a normal variation in sinoatrial (SA) node discharge rate, influenced by autonomic tone.
- Heart rate increases on inspiration (reduced vagal tone) and slows on expiration (enhanced vagal tone) → “respiratory sinus arrhythmia.”
- More prominent in younger individuals due to stronger vagal modulation; tends to fade with age.
📊 ECG Features
- Normal sinus P waves and PR intervals.
- Consistent 1:1 atrioventricular (AV) conduction.
- Beat-to-beat variation in the P–P interval, usually ≥120 ms between the shortest and longest cycle.
- ⚠️ If ≥2 different P-wave morphologies are present → consider atrial ectopy, wandering atrial pacemaker, or another atrial focus instead.
💡 Management
- No treatment required – it is a normal physiological finding.
- Reassure patients, especially the young, that this is harmless and does not progress to pathology.
- Helpful to contrast with true arrhythmias, teaching students to recognise when variation is benign vs. pathological.
| 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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