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Background: Fluid imbalance and malnutrition have an important role in the clinical setting of chronic heart failure (CHF). Recently, tetrapolar bioelectrical impedance analysis has been suggested as an attractive method which may be used in the clinical assessment of the body composition. The aim of this study was to determine the effects of body side on whole bioelectrical impedance analysis parameters and test-retest reliability, prior to its use in a large cohort of patients., Methods: In 114 consecutive patients with CHF (mean age 65 +/- 10 years, left ventricular ejection fraction 31 +/- 9%, NYHA functional class 2.6 +/- 0.9) we measured the total body resistance, the reactance and the derived angle phase using a single-frequency (50 KHz) tetrapolar plethysmograph device. The evaluations were performed on the left and right sides of the body, in a random order, on two different occasions 30 min apart. The effects of body side were analyzed by the Student's t-test and the test-retest reliability was computed by using the coefficient of variation and intraclass correlation coefficient., Results: In both evaluations, the mean resistance value of the right side was significantly lower (almost 10 ohms) than that of the left side, the reactance was not different, and as a consequence the angle phase was significantly higher (almost 0.1 degrees) in the right than in the left side. The test-retest reliability for all the measurements considered was very high (the intraclass correlation coefficient ranged from 0.95 to 0.99 and the coefficient of variation from 1.7 to 4.3%)., Conclusions: In CHF, the body side is important for the whole-body assessment of the resistance and the angle phase, but not for reactance. In addition, all these measurements are characterized by an excellent test-retest reliability and, consequently, do not necessitate a substantial increase in the sample size for the detection of small differences in experimental studies.

The autonomic control of the cardiovascular system plays an important role in maintaining the arterial pressure at the levels necessary for adequate tissue perfusion. In cardiovascular diseases, the impairment of the basic reflex mechanisms that are responsible for the moment-to-moment regulation could increase sympathetic activity and is correlated with an adverse outcome. The objective of the present review was to provide information about the methodological aspects exploring cardiopulmonary and chemoreceptor reflexes. Different techniques are available and all of them include assessment of reflexes through the activation or deactivation of either the cardiopulmonary baroreceptors or chemoreceptors. Intravenous saline load, head-down tilt, passive legs raising, head-out water immersion and the application of a lower body positive pressure are the principal methods utilized for activating cardiopulmonary baroreceptors; on the contrary deactivation could be achieved by acutely induced hypovolemia by furosemide or blood donation, inflation of a congestion cuff on the thighs or application of a negative pressure on the lower body. The transient exposure to a hypoxic or a hypercapnic gas mixture is frequently used to determine the peripheral and central chemoreflexes, respectively. The reflexes are quantified by the gain between output (i.e. heart rate, sympathetic activity, vascular resistance, ventilation) and input (oxygen saturation, end-tidal CO2 or changes in central venous pressure). One important limitation in assessing the cardiopulmonary baroreflex by using currently available techniques is that the involvement of the arterial baroreflex cannot be avoided. In addition, chemoreflexes cannot be interpreted unless the breathing rate is controlled. To date, several techniques are available for the quantification of cardiopulmonary baroreceptor and chemoreceptor reflexes and could provide new information on the abnormal autonomic mechanisms contributing to the pathophysiology of several cardiovascular diseases.

Background: We investigated the effects of subdiastolic variations of the pressure inside the thigh cuffs on cardiovascular oscillations and arterial baroreflex sensitivity in humans., Methods: During 10 min of controlled breathing at low (0.1 Hz) and high (0.25 Hz) frequencies, 30 healthy subjects underwent variations of the pressure inside the thigh cuffs (from 0 to 40 mmHg) at 0.25 and 0.1 Hz respectively; the periods of controlled breathing without cuff pressure modulation were used as a control. The frequency responses of cardiovascular signals were assessed using spectral analysis, and baroreflex sensitivity by the sequence method., Results: Cuff pressure modulation at 0.25 Hz did not affect the RR interval, arterial pressure, or baroreflex sensitivity; at 0.1 Hz it did not change the RR interval and arterial pressure, but engaged (0.76 +/- 0.2 of coherence) and increased the low frequency oscillations of the RR interval (from 5.6 +/- 1 to 6.1 +/- 0.9 ln ms2, p < 0.05) and improved baroreflex sensitivity by 25% (from 14.2 +/- 9 to 17.7 +/- 10 ms/mmHg, p < 0.01)., Conclusions: Subdiastolic thigh cuff pressure modulation at 0.1 Hz improved the low frequency oscillations of heart rate and baroreflex sensitivity. This approach represents a new and simple non-pharmacological strategy for acutely improving baroreflex sensitivity in humans.

Background: It has been hypothesized that hydrophilic and lipophilic beta-blockers have different antiarrhythmic properties because only the latter seem to reduce the rate of sudden death in post-myocardial infarction patients as well as animal models which seem to be independent of their effect on autonomic nervous system modulation. The aim of this study was to evaluate the different effects of a hydrophilic (nadolol) and lipophilic (metoprolol) beta-blocker on ventricular repolarization in normal subjects., Methods: Seventeen normal subjects entered this randomized, single-blind cross-over study designed to compare the effects of nadolol (80 mg/day) and slow-release metoprolol (200 mg/day) on dynamic ventricular repolarization. The RR intervals, the QT evaluated at the apex (QT apex) and at the end (QT end) of the T wave before and after correction for heart rate, the standard deviation of QT apex and QT end, and the slope of the QT/RR linear relationship (QTa-slope and QTe-slope) were studied using the ELATEC system (ELA Medical, Mountrouge, France), and an evaluation was made of their reproducibility and the effects of each beta-blocker., Results: The most reproducible parameters were QT apex, corrected QT apex and the QTe-slope. Nadolol was associated with a greater adrenergic blockade than metoprolol (lengthening of RR interval +25 +/- 7 and +17 +/- 8% respectively, p = 0.0003) and a lower effect on ventricular repolarization (reduction of corrected QT apex -0.6 +/- 3 and -2.5 +/- 2.1% respectively, p < 0.01; reduction of QTe-slope -5 +/- 16 and -15 +/- 15% respectively, p = 0.03)., Conclusions: At the dosages used in the study, metoprolol showed lower adrenergic blockade but greater effect on ventricular repolarization than nadolol.