Prolonged PR interval (first degree heart block) may be normal or be seen in:
- Viral or rheumatic myocarditis and other myocardial dysfunctions
- Certain congenital heart disease (Ebsteins, ECD, ASD)
- Digitalis toxicity
- Hyperkalaemia
Short PR interval occurs in:
- Pre‐excitation (eg Wolff‐Parkinson‐White)
- Glycogen storage disease
Variable PR interval occurs in:
- Wandering atrial pacemaker
- Wenckebach (Mobitz type 1) second degree heart block.
