DM1 – Cardiac Conduction — SCE Neurology MCQ

Correct answer: B — Offer prophylactic permanent pacing after specialist inherited-cardiac review

The best answer is “Offer prophylactic permanent pacing after specialist inherited-cardiac review”. DM1 produces progressive conduction-system disease and sudden atrioventricular block; an HV interval at or above about 70 ms supports prophylactic pacing even before documented complete block. “Reassure because conduction disease is benign in skeletal-muscle disorders” is less appropriate because conduction disease is a major cause of sudden death in DM1 “Start flecainide without providing bradycardia protection” is less appropriate because a sodium-channel blocker can worsen conduction and does not protect against block “Repeat an ECG in two years without rhythm surveillance” is less appropriate because presyncope and advanced conduction delay require action rather than long-interval observation “Use exercise testing alone to exclude progressive His–Purkinje disease” is less appropriate because exercise testing cannot replace invasive evidence of significant infra-His disease

Reference: Clinical care recommendations for cardiologists treating adults with myotonic dystrophy. https://pmc.ncbi.nlm.nih.gov/articles/PMC7070199/