ECG: PR Interval

Key points

• Prolonged PR interval: idiopathic · ischaemic heart disease · digoxin toxicity · hypokalaemia · rheumatic fever
• Also: aortic root pathology (abscess secondary to endocarditis — an indication for surgery) · Lyme disease · sarcoidosis · myotonic dystrophy · athletes
• Hyperkalaemia can rarely prolong the PR interval — a much less common association than hypokalaemia
• A short PR interval is seen in Wolff-Parkinson-White syndrome