Autonomic function and baroreflex sensitivity during angiotensin-converting enzyme inhibition or angiotensin II AT-1 receptor blockade in essential hypertensive patients.

OBJECTIVE: The influence of ACE-inhibition and angiotensin II ATI receptor blockade on the autonomic function and baroreflex sensitivity was investigated in hypertension. METHODS AND RESULTS: Heart rate variability was assessed in a resting condition by power spectrum analysis to evaluate the low frequency (LF) power, high frequency (HF) power and LF/HF ratio in 19 hypertensive patients and 23 normotensive controls. Moreover, the coherence between the tachogram and the systogram was evaluated, and the baroreflex gain (alphaLF-index), describing the transfer function of variability in the systolic pressure signal to variability in the RR interval, was obtained. Then a 24-h ambulatory blood pressure monitoring was performed. The 19 hypertensive patients were randomized to either enalapril or losartan treatment, and after 2 months were re-submitted to the RR variability and baroreflex study and to blood pressure monitoring. The subjects then crossed to the other antihypertensive treatment and were re-evaluated after an additional two months. No significant difference was found either in LF power and HF power and LF/HF ratio between normotensive and hypertensive subjects whereas a slight though significant difference was observed in the alphaLF-index. In hypertensive patients, both the treatments with enalapril and losartan reduced blood pressure and had no effect on heart rate. No significant change was observed in autonomic balance or in baroreflex sensitivity during the two antihypertensive treatments. CONCLUSIONS: In hypertensive patients, the angiotensin system or bradykinins do not seem to have any modulatory effect on the sympathetic/parasympathetic control of blood pressure and baroreflex sensitivity, in a resting condition. Since heart rates were unchanged by the two antihypertensive treatments despite a significant reduction of blood pressure, a resetting of baroreflex function was observed during both ACE-inhibition and angiotensin II ATI receptor blockade.

Autonomic function and baroreflex sensitivity during a normal ovulatory cycle in humans.

OBJECTIVE AND DESIGN: Possible variations occurring in the autonomic function during a normal ovulatory cycle have been poorly investigated and it is not known whether the baroreflex sensitivity may change according to the different phases of the cycle. The aim of this study was to evaluate heart rate variability (power spectrum analysis), and baroreceptor sensitivity (alpha-low frequency coefficient) in 13 young women with regular menses during the two phases of the cycle (phase I: 5 +/- 1 days and phase II: 23 +/- 3 days from bleeding). RESULTS: The low frequency/high frequency ratio was significantly higher in the second phase of the cycle (phase I: 2.8 +/- 2.6; phase II: 5.6 +/- 5.8, p < 0.05), in the presence of increased low frequency and reduced high frequency expressed in normalized units-nu-(phase I: 59.8 +/- 16.7 nu and 32.6 +/- 15.6 nu for low frequency and high frequency, respectively; phase II: 67.7 +/- 18 nu and 25.7 +/- 17.5 nu for low frequency and high frequency, respectively; p < 0.05). The alpha-low frequency coefficient, index of baroreflex sensitivity, did not statistically differ in the two phases (phase I: 10.6 +/- 4.5 msec/mm Hg; phase II: 8.9 +/- 4.9 msec/mm Hg; ns). CONCLUSIONS: The power spectrum analysis suggests that the autonomic function may be affected by the ovulatory cycle, sympathetic activation being relatively increased in the second phase. On the contrary, the baroreceptor function seems to be scarcely influenced by the two phases of the menstrual cycle.

Relationship between dental pain perception and 24 hour ambulatory blood pressure: a study on 181 subjects.

OBJECTIVE: To investigate dental pain perception in a large group of essential hypertensive subjects. METHODS: A total of 130 hypertensive patients together with 51 normotensive subjects were submitted to tooth-electrical stimulation to determine the dental pain threshold (occurrence of pulp sensation) and tolerance (time when the subject asked for the test to be stopped). Blood pressure was measured at rest, before pain perception evaluation, and during a 24 h period by ambulatory monitoring. RESULTS: The normotensive and hypertensive subjects differed with regard to pain threshold (P = 0.002) and tolerance (P = 0.01). Pain perception variables were significantly correlated with both resting blood pressure and 24 h, diurnal and nocturnal arterial pressures, the correlation between pain threshold and 24 h systolic blood pressure being the most significant (r = 0.31, P < 0.0001). By contrast, parameters indicating 24 h blood pressure variability (percentage of nocturnal blood pressure reduction and 24 h blood pressure variation coefficients) were not associated with pain perception. Moreover, among the hypertensives only, a significant relationship was observed between pain sensitivity and both baseline and 24 h pressures. No association was found when pain perception and blood pressure were correlated in the normotensive group. CONCLUSIONS: The correlation between both baseline and 24 h blood pressure and pain perception has been confirmed in a large group study of normotensive and hypertensive subjects. Moreover, even among the hypertensive range of blood pressure, the higher the blood pressure is, the lower the sensitivity to pain is. These findings strengthen the hypothesis of a role of the degree of blood pressure elevation in modulating pain sensitivity.

Treatment with enalapril modifies the pain perception pattern in hypertensive patients.

The cardiovascular system shares numerous anatomic and functional pathways with the antinociceptive network. The aim of this study was to investigate whether angiotensin-converting enzyme (ACE) inhibitor treatment could affect hypertension-related hypalgesia. Twenty-five untreated hypertensive patients, together with a control group of 14 normotensive subjects, underwent dental pain perception evaluation by means of a pulpar test (graded increase of test current applied to healthy teeth). After the evaluation of the dental pain threshold (occurrence of pulp sensation) and tolerance (time when the subjects asked for the test to be stopped), all the subjects underwent a 24-hour ambulatory blood pressure monitoring. The hypertensive group then was treated with 20 mg/d enalapril, whereas the normotensive subjects remained without any treatment. After a time interval of 6+/-2 months, the dental pain sensitivity was retested in all the subjects, and ambulatory blood pressure was recorded during treatment in the hypertensive patients. At the first assessment, hypertensive patients showed a higher pain threshold than normotensive subjects (P<.001). On retesting of pain sensitivity in hypertensive patients, a significant decrease of both pain threshold and tolerance, leading to their normalization, was observed during treatment (P<.001 and P<.005, respectively), in the presence of reduced 24-hour and office blood pressure values. A slight, though significant, correlation was observed between variations in pain tolerance and baseline blood pressure changes occurring during treatment. During follow-up, the normotensive subjects did not show any significant pain perception or office blood pressure changes. Hypertension-related hypalgesia was confirmed. Mechanisms acting both through lowering of blood pressure and specific pharmacodynamic properties may account for the normalization of pain sensitivity observed in hypertensive patients during treatment with ACE inhibitors.

Reactivity of blood pressure to mental arithmetic stress test, stress-test recovery time, and ambulatory blood pressure in hypertensive and normotensive subjects.

BACKGROUND: Laboratory mental stress testing and 24 h ambulatory blood pressure monitoring may analyse reactivity of blood pressure during provoked stress and stressful situations in daily-life, respectively. OBJECTIVE: To evaluate whether the responses to a mental stress test and during the stress-test recovery time were associated with ambulatory blood pressure parameters. METHODS: Fifty-two untreated male subjects (22 normotensives and 30 hypertensives) were subjected both to mental arithmetic stress testing and ambulatory blood pressure monitoring. RESULTS: We found a positive correlation between baseline and peak-test blood pressures during the stress test and 24 h blood pressures. Maximal values of systolic and diastolic blood pressures measured during the 24 h were also correlated to the maximal systolic and diastolic blood pressures reached during the stress test ( P < 0.001). We observed no relationship between reactivity during the stress test and 24 h parameters. On the contrary, changes in diastolic blood pressure during the time of recovery from the stress test (expressed as percentage-change scores) were correlated to the 24 h diastolic blood pressure parameters, the diastolic load being the most closely associated variable. CONCLUSION: The absence of relationships between variations in blood pressure during the provoked stress and ambulatory monitoring parameters indicates that reactivity of blood pressure to an acute stress does not predict the 24 h profile. However, the correlation between the maximal blood pressure measured by ambulatory monitoring and that observed during stress testing indicates that the maximal 24 h values may show the extreme blood pressure response (like the one provoked acutely by a laboratory stress test) of an individual subject. The correlation between the percentage-change score during the recovery time of diastolic blood pressure and the 24 h diastolic load could account forr a lower than normal capacity for recovery of subjects with persistently high blood pressures.

Atrial natriuretic peptide and 24 h blood pressure.

BACKGROUND: Atrial natriuretic peptide (ANP) is a hormone involved in the cardiovascular modulation of blood pressure and volume homeostasis. OBJECTIVE: To compare ANP levels in normotensives and hypertensives and to correlate ANP levels with ambulatory blood pressure parameters. METHODS: Plasma samples for ANP determination (using a double-antibody radioimmunoassay Kit) were obtained from 33 consecutive subjects (24 hypertensives, nine normotensives) who had rested supine for 30 min. Afterwards, all of the subjects were subjected to 24 h non-invasive blood pressure monitoring. We found no significant difference between the two groups with regard to ANP levels (95.1+/-29 versus 96.9+/-33 pg/ml, in normotensives and hypertensives, respectively). Also, when hypertensive patients were divided according to their family history of hypertension, ANP levels were similar. There was no correlation between the ANP level and the pre-sampling blood pressure or between the ANP level and the following ambulatory blood pressure monitoring parameters: 24 h, diurnal and nocturnal systolic and diastolic blood pressures, systolic and diastolic loads, nocturnal blood pressure reduction and blood pressure variation coefficients. CONCLUSION: Both the pre-sampling blood pressure and ambulatory monitoring results (sustained blood pressures and pressure variations during the 24 h period) do not seem to influence basal ANP levels in patients with hypertension. These data do not account for a role of this peptide in cardiovascular control, in hypertension.