6.5
Code 6.5 — Minnesota Code 6-5: short PR interval. The PR interval is shorter than 0.12 s (120 ms) in all beats of at least two limb leads, but the QRS complex is normal and there is no delta wave, so the WPW criteria are not met. The impulse passes from the atria to the ventricles faster than usual. This can be a normal variant, or it can result from enhanced AV-node conduction or an atrial rhythm arising close to the AV node.
Possible causes
- Normal variant, especially in young people and during fast heart rates (sympathetic activation)
- Low atrial or junctional rhythm (the P wave is often negative in II, III, aVF)
- Enhanced AV-node conduction (historically "Lown–Ganong–Levine" pattern)
- Pregnancy, hyperthyroidism, some storage disorders (Pompe, Fabry, Danon disease)
Clinical significance
A short PR with a normal QRS and no symptoms is usually harmless. It deserves attention if there are episodes of palpitations, which may indicate supraventricular tachycardia, or if there are signs of cardiomyopathy such as high voltage or ST-T changes. Without a delta wave, the risk associated with WPW does not apply, but a subtle delta wave can be missed, so careful review by a doctor is useful.
Mention the finding to your doctor, especially if you have episodes of rapid heartbeat. Seek urgent care if you experience fainting or a very fast heartbeat with dizziness.
References
- Prineas RJ, Crow RS, Zhang ZM. The Minnesota Code Manual of Electrocardiographic Findings. 2nd ed. London: Springer; 2010. doi:10.1007/978-1-84882-778-3
- Page RL, Joglar JA, Caldwell MA, et al. 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia. Circulation. 2016;133(14):e506–e574. doi:10.1161/CIR.0000000000000311
This article is for general information and does not replace a consultation with a doctor. ECG findings must be interpreted by a physician together with symptoms and other tests.
Published on 14 May 2019