Causes of a prolonged PR interval

• idiopathic
• ischaemic heart disease
• digoxin toxicity
• hypokalaemia*
• rheumatic fever
• aortic root pathology e.g. abscess secondary to endocarditis
• Lyme disease
• sarcoidosis
• myotonic dystrophy

A prolonged PR interval may also be seen in athletes

A short PR interval is seen in Wolff-Parkinson-White syndrome

*hyperkalaemia can rarely cause a prolonged PR interval, but this is a much less common association than hypokalaemia

PR interval

Prolonged PR: ischaemic heart disease, digoxin toxicity, hypokalaemia, rheumatic fever, aortic root abscess (endocarditis), Lyme disease, sarcoidosis, myotonic dystrophy, athletes

Short PR: WPW;

hyerexcitatory