A 47 year old man developed malaise, fever, and a new aortic regurgitation murmur. Staphylococcus aureus was isolated from blood cultures. An echocardiogram showed vegetations on the bicuspid aortic valve with moderate regurgitation. Antibiotic treatment for endocarditis was instituted. Subsequent ECGs evidenced progressive lengthening of the PR interval, from 230 ms at admission (panel A, upper trace) to 280 ms two days later (panel A, lower trace). Abscess formation in the aortic root was suspected and confirmed by transoesophageal echocardiography (panel B, arrow).

At surgery, endocarditis with para-aortic abscess formation was confirmed. After debridement and valve replacement, total atrioventricular block ensued for which a DDD pacemaker was implanted. Thereafter, the patient recovered uneventfully during a six week course of antibiotics.

The ECG is useful for risk stratification of aortic valve endocarditis. Due to the anatomic relation of the aortic root and cardiac conduction system, atrioventricular conduction slowing can occur when infection spreads transmurally across the aortic root. Hence, PR lengthening portends a poor prognosis. Daily electrocardiography should therefore be pursued.