Heart Rate Variability (HRV): a mini-review of its basic principles and applications in vascular diseases

Heart rate variability (HRV) is a biomarker which is strictly related to the activity of the autonomic nervous system (ANS). It has also been demonstrated that HRV is strictly related to human psycho-physical resilience and, more generally, to human health and aging. The analysis of HRV through different methods, mostly of photoplethysmographic type, is being increasingly employed in several medical disciplines, both as a diagnostic tool and as a prognostic mean to monitor a number of treatments. ANS notoriously influences a wide spectrum of human physiological processes and its unbalance brings several alterations in a number of pathophysiology processes related to cardiovascular diseases and psycho-neuro-biology in general. The HRV analysis technique includes a basal and under "stress"examination, to elicit a series of time-domain and frequency-domain-based parameters which highlight the orthosympathetic and parasympathetic (vagal) activities. The usage of HRV analysis in vascular diseases may be of interest in a few cases, such as: the diabetic dysautonomia and microangiopathy, the vaso-dystonic acro-syndromes (e.g. Raynaud phenomenon), the autoimmune disease-based "vasculitis" and more generally any vascular ulcer, lymphedema and all types of microangiopathies and cardiovascular diseases. This mini-review describes the basic principles of HRV analysis and its applications in the diagnostic-therapeutic approach to vascular diseases.