Conduction Disease in Amyloidosis — EECC MCQ

Correct answer: C — Amyloid infiltration of the cardiac conduction system — amyloidosis frequently causes conduction disease (AV block, bundle branch block, sinus node dysfunction) due to direct infiltration of the conduction tissue with amyloid fibrils

Cardiac amyloidosis commonly causes conduction system disease through direct infiltration of the sinoatrial node, AV node, His bundle, and bundle branches with amyloid fibrils. Conduction abnormalities in amyloidosis include: (1) AV block (first, second, and third degree — may require pacing); (2) bundle branch block (LBBB or RBBB); (3) sinus node dysfunction (chronotropic incompetence, sinus pauses); (4) low-voltage QRS (paradoxically, despite LVH — because amyloid is electrically inert, replacing functional myocardium). In AL amyloidosis, conduction disease may be rapidly progressive. In ATTR, progression is usually more gradual. The 2023 ESC Cardiomyopathy Guidelines note that pseudoinfarction pattern (Q waves without MI) is common. Pacemaker implantation follows standard bradycardia indications. Importantly, low voltage + LVH on echo (voltage-mass mismatch) is a classic amyloidosis 'red flag.'

Reference: ESC (2023): Cardiomyopathies Guidelines