Assessment of cardiovascular autonomic function in myotonic dystrophy type 2 (DM2/PROMM).
BACKGROUND
Proximal myotonic myopathy is an autosomal dominant multisystem disorder with a recently defined CCTG expansion on chromosome 3 in the major subgroup (myotonic dystrophy type 2). Cardiac rhythm disturbances have been described in patients with this disease, but it is not known whether myotonic dystrophy type 2/proximal myotonic myopathy patients suffer from dysautonomia and whether cardiac arrhythmias relate to autonomic dysfunction.


OBJECTIVE
To investigate cardiovascular autonomic function in myotonic dystrophy type 2/proximal myotonic myopathy patients with and without cardiac arrhythmias.


METHODS
Standard autonomic function tests (heart rate responses to Valsalva manoeuvre, deep breathing and active change of posture, and blood pressure responses to active change of posture and sustained handgrip), resting heart rate variability in the time- and frequency-domain, and the corrected QT interval length were determined in 16 patients with genetically defined myotonic dystrophy type 2/proximal myotonic myopathy and compared to the results obtained in 16 age- and sex-matched healthy control subjects.


RESULTS
Standard autonomic tests yielded similar results in both groups. Measures of heart rate variability tended to be lower in myotonic dystrophy type 2/proximal myotonic myopathy patients compared to healthy controls, but reached statistical significance only for the number of R-R intervals exceeding 50 ms (p50) and the power spectrum density in the low-frequency range (low-frequency power). Four patients (25%) suffered from mild cardiac rhythm disturbances encompassing paroxysmal tachycardia, sinoatrial block, right bundle branch block, ventricular premature beats and bradycardia. The autonomic responses of these patients were essentially similar compared to those without cardiac arrhythmias, apart from a decreased heart rate response to deep breathing in the patients with cardiac arrhythmias.


CONCLUSIONS
We found no major abnormalities of cardiovascular autonomic function in patients with myotonic dystrophy type 2/proximal myotonic myopathy, neither in the whole study group nor in the subgroup of patients with cardiac rhythm abnormalities.
Flachenecker
Peter
P
Department of Neurology, Julius-Maximilians-Universität Würzburg, Josef-Schneider-Strasse 11, D-97080 Würzburg, Germany.
Schneider
Christiane
C
Cursiefen
Simone
S
Ricker
Kenneth
K
Toyka
Klaus V
KV
Reiners
Karlheinz
K
D000328:Adult; D001145:Arrhythmias, Cardiac / Q000503:physiopathology; D001341:Autonomic Nervous System / Q000503:physiopathology*; D001794:Blood Pressure; D002320:Cardiovascular Physiological Phenomena; D002319:Cardiovascular System / Q000503:physiopathology*; D016022:Case-Control Studies; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D020967:Myotonic Disorders / Q000503:physiopathology; D009223:Myotonic Dystrophy / Q000503:physiopathology*; D011187:Posture; D012119:Respiration; D014636:Valsalva Maneuver