[Blood pressure variability]

This review deals with a number of issues related to blood pressure variability. These include: historical aspects, with reference to the first pioneering observations; methodological aspects, focusing on the different methods for quantifying blood pressure variability; description of the characteristics of blood pressure variability over the 24 hours; mechanisms involved in determining the different magnitude of this phenomenon in different subjects, such as behavioral factors, central and reflex neural influences, humoral and mechanical factors; blood pressure variability as a probe to assess spontaneous baroreflex sensitivity; effects of aging and hypertension on blood pressure variability, with a discussion of the clinical relevance of this phenomenon in the prognostic evaluation of patients; effects of drugs on blood pressure variability. Finally methodological aspects related to the use of noninvasive ambulatory blood pressure monitoring in the assessment of blood pressure variability are discussed.

Different baseline sympathovagal balance and cardiac autonomic responsiveness in ischemic and non-ischemic congestive heart failure

BACKGROUND

A profound autonomic unbalance is present in heart failure: its correlation with the etiology of the disease has never been investigated.

AIMS

We characterized the sympatho-vagal balance and autonomic responsiveness of 42 patients (21 with ischemic heart failure, 21 with idiopathic dilated cardiomyopathy). Patients had comparable NYHA class, ejection fraction, exercise pVO(2), exercise ventilatory response, incidence of beta-blocking treatment. None showed periodic breathing or nocturnal arterial desaturation.

METHODS

Heart rate variability was assessed in the time and frequency domain during: (1) 10 min of quiet supine resting and free breathing; (2) 10 min of regular breathing at a frequency of 20 acts/min (=parasympathetic stimulus); and (3) 10 min of active standing (=sympathetic stimulus). The ratio of the low- to high-frequency components of each autospectrum obtained in the frequency domain (LF/HF) was used as an index of sympathovagal balance.

RESULTS

Patients with ischemic heart failure had a greater baseline sympathetic activation (higher LF/HF) than those with idiopathic dilated cardiomyopathy, maintaining some parasympathetic responsiveness as well (reduced LF/HF with regular breathing).

CONCLUSIONS

There is a distinct autonomic control according to the etiology of heart failure, a finding that may help understanding its pathophysiology, and could be useful in the clinical management of patients.