Heart rate variability measurement in diabetic neuropathy: review of methods.

Heart rate variability (HRV) is an important tool to analyze the autonomic function. It therefore has a special interest for early detection and ensuing treatment of autonomic neuropathy in diabetic patients. The aim of this work is to present a brief historical review of HRV, as well as a technical review of the most common methods to measure it. In this work is presented a system that performs three measurements of HRV. An overview of methodologies developed to quantify HRV is presented; this technical review covers the most common time and frequency domain techniques, for short and long periods of time, with comments about clinical utility of these tests. A system performing three standard tests of HRV, Anscore Health Management System, is presented. This system performs metronomic breathing (MT), the Valsalva Test (VT), and the Stand Test (ST). A normal range study with 212 healthy subjects in three centers (ages 20-80 years, with even age distribution, and even male and female distribution) was conducted. A subset of 45 subjects from the total number of subjects was selected for the reproducibility study, consisting of three measurements of each test. The normal range study showed a decrease in all the ratios with age and, for the Valsalva test, a difference among genders; 5th percentiles were calculated. The reproducibility study results, expressed as mean CV%, were 4.30% for the MT, 6.26% for the VT, and 6.66% for the ST. HRV is the most reliable measurement of autonomic function; when controlled maneuvers like MT, VT, and ST are performed, high reproducibility is obtained, with results comparable to that observed for nerve conduction studies. Such reproducibility makes autonomic function testing more feasible as a test component in multicenter studies of different neurological disorders.