Autonomic dysfunction presenting as orthostatic intolerance in patients suffering from mitochondrial cytopathy.
BACKGROUND
Disturbances in autonomic nervous system function have been reported to occur in patients suffering from mitochondrial cytopathies. However, there is paucity of literature on the occurrence of orthostatic intolerance (OI) in these patients. We report on a series of patients diagnosed with mitochondrial cytopathy who developed features of autonomic dysfunction in the form of OI.


METHODS
This was a single-center report on a series of 6 patients who were followed in our clinic for orthostatic intolerance. All of these patients had a diagnosis of mitochondrial cytopathy on the basis of muscle biopsy and were being followed at a center specializing in the treatment of mitochondrial disorders. This study was approved by our local institutional review board. Each of the patients had suffered from symptoms of fatigue, palpitations, near syncope, and syncope. The diagnosis of OI was confirmed by head-up tilt test. Collected data included demographic information, presenting symptoms, laboratory data, tilt-table response, and treatment outcomes.


RESULTS
Six patients (3 females) were identified for inclusion in this report. The mean age of the group was 48 ± 8 years (range, 40-60 years). All of these patients underwent head-up tilt table testing and all had a positive response that reproduced their clinical symptoms. Among those having an abnormal tilt-table pattern, 1 had a neurocardiogenic response, 1 had a dysautonomic response, and 4 had a postural orthostatic tachycardia response. All but 1 patient reported marked symptom relief with pharmacotherapy. The patient who failed pharmacotherapy received a dual-chamber closed-loop pacemaker and subsequently reported marked improvement in her symptoms with elimination of her syncope.


CONCLUSIONS
Orthostatic intolerance might be a significant feature of autonomic nervous system dysfunction in patients suffering from mitochondrial cytopathy.
Section of Electrophysiology, Division of Cardiology, Division of Internal Medicine.
Khalil
K
Kanjwal
Section of Electrophysiology, Division of Cardiology, Division of Internal Medicine.
Beverly
B
Karabin
Section of Electrophysiology, Division of Cardiology, Division of Internal Medicine.
Yousuf
Y
Kanjwal
Department of Medicine, The University of Toledo Medical Center, Toledo, Ohio.
Bilal
B
Saeed
Section of Electrophysiology, Division of Cardiology, Division of Internal Medicine.
Blair P
BP
Grubb
D000328:Adult; D001342:Autonomic Nervous System Diseases / Q000150:complications / Q000503:physiopathology* / Q000628:therapy; D002304:Cardiac Pacing, Artificial / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007625:Kearns-Sayre Syndrome / Q000150:complications / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D017240:Mitochondrial Myopathies / Q000150:complications / Q000503:physiopathology; D054971:Orthostatic Intolerance / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology*; D011379:Prognosis; D013575:Syncope / Q000209:etiology* / Q000503:physiopathology / Q000628:therapy; D018667:Tilt-Table Test