Autonomic dysregulation in essential hypertension: insight from heart rate and arterial pressure variability

Essential hypertension is the most prevalent cardiovascular disorder, affecting more than 50 million people in the USA. Hypertension-related mortality and morbidity figures have been greatly improved over the last three decades by major advances in prevention. Detection and operative suggestions for practicing physicians are available from several guideline treatments derived from grouped data obtained in numerous well-conducted studies on large numbers of patients. However, the disappointing results of some forms of antihypertensive therapies, particularly in preventing coronary artery disease, has shed some doubts on traditional approaches to managing hypertensive patients. At present, in spite of extensive investigations, the exact causal mechanism(s) are far from being fully understood, and consequently, essential hypertension is still managed using a heuristic approach. Persistent elevations in arterial pressure imply some disturbances in the complex and multifactorial cardiovascular control mechanisms. In this context, neurohumoral disturbances might play a special role, in view of the demonstration that an elevated sympathetic drive seems essential in hypertensive patients. In this review, we follow the hypothesis that other allied methods capable of quantitatively assessing some aspects of the regulatory system might support and integrate the usual dichotomous diagnostic procedure based on arterial pressure determinations. In prior studies, we reported that parameters obtained by spectral analysis of heart rate variability (HRV) might furnish useful information on autonomic normal and abnormal nervous system regulation. In the foregoing, we summarize our experience using this approach in the clinical management of hypertensive patients. It is our tenet that spectral analysis of mono or multivariate cardiovascular beat-by-beat variabilities provides potentially important information on alterations in neural control of the circulation accompanying essential hypertension. In spite of an ongoing debate on the interpretation of specific aspects of HRV spectral components, overall, it appears that the available evidence supports the hypothesis that in essential hypertension, there is an increased sympathetic and reduced vagal cardiac drive coupled with an enhancement of vasomotor sympathetic modulation. Prospective studies on large populations, rendered more easy to perform, thanks to improvements in technology and telemedicine applications, might provide an answer to the still open question of how to apply spectral analysis of HRV to a better mechanistic understanding of essential hypertension, and to more satisfactory individually tailored antihypertensive treatments.