Objectives: To assess the function of the autonomic nervous system in patients with acute intermittent porphyria by spectral analysis of the heart rate variability.
Design: A cross-sectional case-control study.
Setting: Patients were examined at the Primary Health Care Centre, Arjeplog and at Umeå University Hospital, where the controls were also examined.
Subjects: Twenty-three patients with acute intermittent porphyria verified by DNA analysis and 92 healthy controls were included.
Main outcome measures: The mid-frequency band power after tilting was used to evaluate sympathetic function, and the high frequency band power during controlled breathing at 12 breaths min-1 and the mid-frequency band power during controlled deep breathing at 6 breaths min-1 were used to evaluate parasympathetic function.
Results: There was no evidence of sympathetic dysfunction in the patients. The mid-frequency band power during controlled deep breathing at 6 breaths min-1 was significantly (P = 0.02) lower in the patient group.
Conclusions: Our findings indicate a parasympathetic dysfunction in patients with acute intermittent porphyria. This may be causally related to sudden cardiac death and the life-threatening arrhythmias which have been observed in this disorder.