Heart rate variability in patients with secondary amyloidosis.

Heart rate variability (HRV) is increasingly being used to evaluate the function of the autonomic nervous system. Although autonomic dysfunction has been described in primary amyloidosis patients, this has not been established for patients with secondary amyloidosis. This study examines the autonomic function of 23 biopsy-proven secondary amyloidosis patients (10 male, 13 female) and compares it with 19 healthy (8 male, 11 female) sex- and age-matched controls (Group III), using frequency- and time-domain HRV analysis. The study group was further divided according to renal function; Group I (14 nonuremic patients with serum creatinine level < 1.4 mg/dl) and Group II (9 uremic patients with serum creatinine level > 1.4 mg/dl). In time domain analysis, standard deviation and mean of the standard deviation of all normal R to R intervals, and standard deviation of the average normal R to R interval were significantly lower in Groups I and II as compared to Group III. In frequency domain analysis, low frequency power (LF), representing sympathetic function, was significantly lower in Groups I and II as compared to Group III, but high frequency power (HF), representing parasympathetic function, and the LF/HF ratio, as an index of sympathovagal balance, were not different among the groups. In conclusion, in patients with secondary amyloidosis, sympathetic components of heart rate variables decreased before the onset of uremia and the change became more prominent with the appearance of uremia despite not reaching statistical significance.