Sinus Arrhythmia
normalSinus Arrhythmia
A normal variant where the heart rate cyclically increases with inspiration and decreases with expiration. Mediated by vagal tone fluctuations during the respiratory cycle. Common in young, healthy individuals.
- Irregular rhythm (RR intervals vary)
- P-P intervals vary with breathing
- Normal P wave morphology (same SA node)
- Normal PR interval and QRS
SA node rate speeds up with inspiration, slows with expiration — mediated by vagal tone changes
During inspiration, intrathoracic pressure decreases and venous return increases. This reduces vagal tone, allowing the SA node to fire faster. During expiration, vagal tone increases, slowing the SA node. This creates cyclic heart rate variation synchronized with the respiratory cycle.
- Irregular rhythm with P-P intervals that vary with respiration.
- P-wave morphology remains constant (same SA node origin).
- PR interval and QRS are normal.
Benign normal variant — sign of healthy autonomic function
Primary Treatment
No treatment needed.
Additional Options
Disappears with exercise or breath-holding.
Long-term Management
Its presence actually indicates healthy cardiovascular regulation.