Renata Carra

Heart rate variability in childhood obesity.

Obesity is characterized by hemodynamic and metabolic alterations. Autonomic control on cardiac function involvement is controversial. The aim of the study was to assess early sign of cardiac autonomic dysfunction in obesity, using time- and frequency-domain heart rate variability (HRV) analysis in a pediatric population. Methods: 32 obese children (OB) (17 M, 15 F; 13.9±1.7 y) were compared with 13 healthy lean subjects (7M, 6F; 12.9±1.6y). For each participant, the authors performed a clinical examination, laboratory testing, blood pressure (BP) measurements, and 24-hour electrocardiograph/ambulatory BP monitoring. The spectral power was quantified in total power, low-frequency (HF) power, index of sympathetic tone, high-frequency (HF) power, index of vagal tone, and LF/HF ratio. Low frequency and HF were averaged to obtain 3 measures: 24-hour, daytime, and nighttime levels. Total, long-term, and short-term time-domain HRV values were calculated. Results: The obese children had higher casual and ambulatory BP, and higher fasting glucose, insulin, and triglyceride levels. Overall HRV values were not significantly lower in OB. The obese children had significantly lower 24-hour and nighttime high-frequency normalized units, and time-domain measures of vagal activity. Low-frequency power showed an inverse but not significant pattern. The OB group had significantly greater 24-hour and nighttime LF/HF ratios. Conclusions: The authors found an increase in heart rate and in BP associated with parasympathetic heart rate control decrease in stabilized obese normotensive children.

AMBULATORY BLOOD PRESSURE MONITORING AND CLINICAL CHARACTERISTICS OF THE TRUE AND WHITE-COAT RESISTANT HYPERTENSION

The resistant hypertension has been differentiated in true resistant hypertension and white-coat resistant hypertension by using ambulatory blood pressure monitoring. White-coat resistant hypertension was defined as high clinic blood pressure, despite triple treatment for at least 3 months, but day-time blood pressure values < 135/85 mmHg. The aim of this study was to evaluate the presence of different clinical characteristics between two types of resistant hypertension. The study group consisted of 49 patients with essential hypertension, resistant to an adequate and appropriate triple-drug therapy, that included a diuretic, with all 3 drugs prescribed in near maximal doses and that had persistently elevated clinic blood pressure (>140/90 mm Hg), for at least 3 months. They represented the 2% of 2500 hypertensive outpatients that referred at our Hypertension Unit. Patients with white-coat resistant hypertension (n=19) were older (p<0.05) than those with true resistant hypertension (n=30). The sodium intake (p<0.05) and alcohol intake (p<0.05) were significantly higher in patients with true resistant hypertension than in those with white-coat resistant hypertension. The renin plasma activity and plasma aldosterone were higher (p<0.05) in patients with true resistant hypertension than in those with white-coat resistant hypertension with normal plasma electrolyte balance. There were no significant differences in mean values of office systolic and diastolic blood pressures between white coat resistant hypertensives and true resistant hypertensives (165+17 vs 172+28 and 98+12 vs 102+14 mmHg). Day-time and night-time ambulatory 24-h-systolic and diastolic blood pressures were significantly higher in the true resistant hypertensive patients when compared with white-coat resistant hypertensives (153+15 vs 124+10 mmHg and 97+9 vs 76+6 mmHg all p<0.001). Day-time and night-time ambulatory 24-h-heart rate were significantly higher in the true resistant hypertensive patients when compared with white-coat resistant hypertensives (79+11 vs 71+9 beats/min;p<0.01; 68+9 vs 60+6 beats/min. p<0.001). The ABP readings were analysed by a Fourier series with 4 harmonics. According to the runs test both two groups of patients showed a circadian rhythm for both systolic and diastolic blood pressure. The nocturnal fall in SBP, DBP and HR was not different in both groups of patients. In conclusion, our findings showed that true resistant hypertensive patients were characterized both by higher heart rate and higher plasma renin activity values as an expression of a possible increased sympathetic activity. Thus, the combination of ABPM with the assessment of the clinical characteristics allow to differentiate better the true drug-resistant hypertension from the white coat resistant hypertension.

Bradykinin B2 receptor gene (-58T/C) polymorphism influences baroreflex sensitivity in never-treated hypertensive patients.

Background Most evidence currently favours a fundamental role of the autonomic nervous system in the pathogenesis of essential hypertension. Recent studies suggest that about 40% of baroreflex variation, an index of cardiac autonomic control, is influenced by genetic factors. Methods and results The aim of this study was to investigate the effect of a common polymorphic variant of the bradykinin B2 receptor gene (B2R; −58T/C) on the autonomic regulation of baroreflex sensitivity (BRS) in 129 mild–moderate never-treated hypertensive patients. No significant differences were found for clinical and biochemical parameters among genotypes. BRS increased with the number of B2R T alleles. B2R genotype was a strong independent predictor of BRS, accounting for 12% of its variation. We suggest that a decrease in the transcription of the bradykinin B2R gene in the presence of the B2R −58C allele could reduce BRS via the diminished effect of bradykinin. Conclusions B2R genotype can explain part of the BRS variation that is unaccounted for by simple anthropometric variables and common risk factors.

Heart Rate Variability and Baroreflex Sensitivity during Fosinopril, Irbesartan and Atenolol Therapy in Hypertension

ObjectiveTo evaluate the effects of long-term therapy with fosinopril, irbesartan and atenolol on the autonomic control of the cardiovascular system in hypertensive patients.MethodsWe enrolled 58 patients (mean age 38 ± 10 years) with never-treated mild hypertension with no evidence of target organ damage. The study was single blind. Patients were assigned to receive fosinopril 10–20 mg/day, irbesartan 150–300 mg/day or atenolol 50–100 mg/day for 14 weeks. Dosage was titrated to reach an average office blood pressure (BP) of <140/90mm Hg. Before therapy all patients underwent a 24-hour Holter ECG to evaluate heart rate variability (HRV) through nonlinear methods, 24-hour ambulatory BP monitoring (ABPM), and measurement of baroreflex sensitivity (BRS) using a Portaprés device; all measurements were repeated after therapy.ResultsAll three therapies significantly and equally decreased BP, both office (systolic/diastolic blood pressure 152 ± 11/97 ± 7mm Hg vs 129 ± 7/85 ± 4mm Hg after fosinopril, 151 ± 11/97 ± 6mm Hg vs 133 ± 9/87 ± 8mm Hg after irbesartan, 149 ± 13/96 ± 9mm Hg vs 132 ± 9/87 ± 7mm Hg after atenolol; p < 0.001) and ABPM values. HRV calculated with nonlinear methods and BRS were significantly increased after atenolol whereas no significant change was found in the fosinopril and irbesartan treatment groups.ConclusionsAll three therapies significantly and similarly reduced BP without modifying heart rate, except for atenolol, which significantly decreased it. Although angiotensin directly increases sympathetic tone, neither fosinopril nor irbesartan modified cardiovascular autonomic function; this is likely to be connected to the fairly good basal autonomic function of the population evaluated. Atenolol is associated with a significant increase in HRV and BRS probably through an improvement of parasympathetic tone.