Autonomic dysfunction in dizzy patients revealed by pulse analysis

Autonomic dysfunction is prevalent in dizzy patients. However, evaluating the autonomic nervous system is not very popular, since it is not easy to do. The Pulse Analyzer Plus® is a small device that measures a patient's pulse from his/her finger tip with a small probe, making it possible to evaluate autonomic nervous system function in as little as 5 minutes. The algorithm is identical to the one used in the frequency analysis of electrocardiograms. We report herein on our findings on the autonomic function of 25 dizzy patients who visited our department. Age-matched control data were obtained from healthy volunteers and patients not suffering from dizziness. The measurements were conducted in 5 minutes with the patient in the sitting position. Fast Fourier Transform (FFT) was used to calculate low frequency (LF) components, which mainly reflect sympathetic nervous system function, and high frequency (HF) components, which reflect parasympathetic nervous system (PNS) function. Natural logarithm (Ln) values were calculated for LF and HF components and used for conventional comparison. The ratio of LF/HF was also calculated. The results of the normal controls were LnLF = 5.2 ± 1.6 (mean ± SD), LnHF = 4.3 ± 1.2, LnLF/HF = 1.2 ± 0.3 whereas those of the dizzy patients were 4.4 ± 1.9, 3.5 ± 1.2 and 1.3 ± 0.5 respectively. The HF value of the dizzy patients was significantly smaller than that of the control subjects (P<0.05). These data indicate that PNS hypofunction was present in the dizzy patients. Future studies need to determine whether autonomic dysfunction results from the therapeutic interventions used to treat dizziness.