Assessment of autonomic nerve function in familial amyloidotic polyneuropathy: a clinical study based on spectral analysis of heart rate variability

We used a novel method based on spectral analysis of heart rate variability to assess selectively sympathetic and parasympathetic engagement in 17 consecutive patients with the Swedish type of familial amyloidotic polyneuropathy (FAP). The findings were compared with those in healthy controls after age-adjustment. All patients had at least one clinical symptom known to be associated with autonomic neuropathy. The high and medium frequency spectral band power, which indicate vagal and sympathetic activities, respectively, were significantly lower in the patients (p < 0.001) indicating severe sympathetic and parasympathetic neuropathy. The patients were divided in three subgroups according to the severity of their neurological handicap. A high-degree reduction in spectral band power was seen in all three subgroups, and there were no significant differences between the groups. This study shows that severe neuropathy is common in FAP, and that the autonomic neuropathy occurs early in the course of the disease. We believe that spectral analysis might be of value in increasing our understanding of the pathophysiology in FAP and in assessing prognosis. Our findings might also be relevant to other forms of systemic amyloidosis.