20
Myotonic Dystrophy Types 1 and 2
Table 4. Clinical scenarios for the management of
arrhythmias in DM1
Clinical scenario
DM1
1. A 63-year-old man with DM1 and minimal neuromuscular impairment presents
with a single episode of unprovoked syncope and facial injury. ECG shows sinus
rhythm, PR interval 180 ms, and RBBB (QRS duration 140 ms). Echocardiogram
shows global LVEF 50% and mild mitral regurgitation.
2. A 52-year-old man with DM1 and mild neuromuscular impairment reports limiting
exertional dyspnea when ambulating and climbing stairs. ECG and 48-Holter
monitor show sinus rhythm with 3:2 and 4:3 type 1 second-degree AV block
(Wenckebach type), and RBBB. Echocardiogram demonstrates LVEF 39% with
global hypokinesis and mild to moderate mitral regurgitation. He is normotensive
on losartan with avoidance of beta-adrenergic blockade due to bradycardia.
