Cardiac autonomic function in type 1 and type 2 myotonic dystrophy.

Area of Science:

• Cardiology
• Neurology
• Autonomic Function Testing

Background:

• Myotonic dystrophy (DM) is a multisystem disorder with potential cardiac involvement.
• Cardiac autonomic nervous system (CANS) function is crucial for cardiovascular health.
• Assessing CANS function in DM patients without overt cardiac disease is important for early detection and management.

Purpose of the Study:

• To evaluate CANS function in DM patients using Holter-derived and standard electrocardiographic parameters.
• To compare CANS function between DM type 1 (DM1) and DM type 2 (DM2) patients and healthy controls.
• To investigate the utility of heart rate turbulence and QT dispersion in detecting subclinical cardiac autonomic dysfunction in DM.

Main Methods:

• Eighty-four DM patients (44 DM1, 40 DM2) and age-matched controls underwent standard ECG and 24-h Holter monitoring.
• Parameters assessed included QT interval dispersion, time-domain heart rate variability (HRV), and heart rate turbulence (HRT).
• Exclusion criteria ensured no conditions influencing cardiac autonomic function were present.

Main Results:

• No significant differences in time-domain HRV were found between DM patients and controls.
• Heart rate turbulence parameters (turbulence onset and slope) were significantly impaired in DM1 and DM2 patients compared to controls.
• QT dispersion was significantly increased in both DM1 and DM2 patients relative to their respective controls.

Conclusions:

• Impaired heart rate turbulence and increased QT dispersion suggest cardiac autonomic nervous system dysfunction in DM patients, even with normal time-domain HRV.
• These findings highlight the sensitivity of HRT and QT dispersion in detecting subclinical autonomic dysfunction in DM.
• This study is the first to examine both HRT and QT dispersion in both DM1 and DM2 patients.