Heart rate variability and autonomic diabetic neuropathy

Aim of this paper is to briefly summarize available evidence about potential usefulness of heart rate variability (HRV) analysis for the clinical evaluation of autonomic diabetic neuropathy. HRV contains hidden information that can be extracted from tachogram sections of several hundred beats with spectral analysis. Subsequent normalization and the use of a paradigm including standardized stimuli (such as tilt) are commonly employed to assess autonomic cardiac regulation. In the resulting spectra, two major components of similar amplitude are usually observed (at low--LF--and high frequency--HF), their relative power is best appreciated using normalized units that provide an estimate of the balance between sympathetic and vagal modulatory activity. In states of sympathetic predominance, such as during orthostatic positions, LF increases and HF decreases. In diabetics, consistent alterations in spectral properties are a frequent early finding: initially a reduction of HRV (ie spectral power) is followed by progressive functional denervation, which is associated to severe autonomic dysfunction. The spectral methodology provides some useful potential advantages in respect to the more traditional approach employing several simple bedside tests. In conclusion, spectral analysis of HRV appears a convenient method to assess various degrees of diabetic autonomic dysfunction: it appears easy to perform, while giving results similar to traditional methods, with greater sensibility.