Assessment of autonomic nerve function in acute intermittent porphyria: A study based on spectral analysis of heart rate variability

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 Umea 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.