AV Block as Abscess Sign in IE — EECC MCQ

Correct answer: D — New AV block in IE suggests perivalvular abscess extending to involve the conduction system — this is a Class I indication for urgent surgery as antibiotics cannot penetrate avascular abscess cavities; the AV node/His bundle lies in close proximity to the aortic root

New conduction disturbance (AV block, bundle branch block, fascicular block) during active IE is a RED FLAG for perivalvular abscess extension into the cardiac conduction system. Anatomical basis: the AV node and His bundle lie in the fibrous trigone adjacent to the aortic root and mitral annulus — aortic valve IE with root abscess can directly invade these structures. The 2023 ESC IE Guidelines classify new conduction disturbance in IE as: (1) strong evidence of perivalvular extension; (2) an indication for urgent surgery (Class I — uncontrolled infection with perivalvular abscess). Imaging: TOE is essential (sensitivity ~90% for perivalvular abscess vs ~50% for TTE); cardiac CT provides complementary anatomical detail. The combination of persistent fever + new AV block + bacteraemia = very high probability of abscess requiring surgery. Serial ECG monitoring is recommended for all patients with aortic valve IE to detect new conduction abnormalities early.

Reference: ESC (2023): IE Guidelines