Andrea Conterno

Assessing resting heart rate in adolescents: determinants and correlates.

The aim of this study was to evaluate the distribution of resting heart rate and its biological and environmental determinants in adolescents. The study was cross- sectional and the population consisted of 2230 children and adolescents, age range 12–18 years, enrolled randomly from state schools in Turin, Italy. In all participants the following parameters were evaluated: heart rate, blood pressure (BP), weight, height, degree of sexual development, physical activity, parental socio-cultural level. Heart rate and BP were measured after 5, 10 and 15 min in a sitting position. Furthermore, to obtain regression equations to define heart rate as a function of the other variables available, a multiple regression analysis was performed. In both sexes BP, but not heart rate, declined significantly from the first to the last determination. Heart rate was positively and significantly correlated to BP level in both sexes; heart rate was higher in girls (3 bpm) and followed a progressive decreasing trend with age in both sexes, that was opposite to BP values. Age, sexual maturation, height, physical activity and parental socio-cultural level were independent determinants of resting heart rate. In conclusion, resting heart rate in adolescents is related to several methodological, constitutional and environmental factors that have to be taken into account when assessing heart rate values and constructing tables of normal values.

α1-Adrenergic Receptor Subtypes in Human Peripheral Blood Lymphocytes

We investigated the expression of alpha1-adrenergic receptor subtypes in intact human peripheral blood lymphocytes using reverse transcription-polymerase chain reaction (RT-PCR) and radioligand binding assay techniques combined with antibodies against the three subtypes of alpha1-adrenergic receptors (alpha1A, alpha1B, and alpha1D). RT-PCR amplified in peripheral blood lymphocytes a 348-bp alpha1A-adrenergic receptor fragment, a 689-bp alpha1B-adrenergic receptor fragment, and a 540-bp alpha1D-adrenergic receptor fragment. Radioligand binding assay with [3H]prazosin as radioligand revealed a high-affinity binding with a dissociation constant value of 0. 65+/-0.05 nmol/L and a maximum density of binding sites of 175. 3+/-20.5 fmol/10(6) cells. The pharmacological profile of [3H]prazosin binding to human peripheral blood lymphocytes was consistent with the labeling of alpha1-adrenergic receptors. Antibodies against alpha1A-, alpha1B-, and alpha1D-receptor subtypes decreased [3H]prazosin binding to a different extent. This indicates that human peripheral blood lymphocytes express the three alpha1-adrenergic receptor subtypes. Of the three different alpha1-adrenergic receptor subtypes, the alpha1B is the most represented and the alpha1D, the least. Future studies should clarify the functional relevance of alpha1-adrenergic receptors expressed by peripheral blood lymphocytes. The identification of these sites may represent a step for evaluating whether they represent a marker of alpha1-adrenergic receptors in cardiovascular disorders or for assessing responses to drug treatment on these receptors.

Circadian Blood Pressure Patterns and Life Stress

Background: Scarce data are available on the influence of psychological aspects on 24-hour ambulatory blood pressure patterns either in normotensive or hypertensive subjects. This study was designed to evaluate the relationship between psychological profile and changes in daytime/nighttime blood pressure rhythm. Methods:Nocturnal dipping was defined as the night/day ratio of ambulatory mean systolic and/or diastolic blood pressure ≤0.87. Three-hundred and two outpatients (M/F = 174/128; mean age = 49.8 years, SD = 13.6; range, 16–80 years) underwent 24-hour ambulatory blood pressure monitoring. They were administered a self-rating scale, the Psychosocial Index, as an indicator of stress, psychological distress, sleep disturbances, well-being, abnormal illness behavior and quality of life. There were 242 patients taking antihypertensive medication (146 adequately controlled and 96 not controlled) and 60 who were drug free (33 never-treated hypertensive and 27 normotensive subjects). Patients were divided according to the presence (n = 125) or absence (n = 177) of night blood pressure dipping. The two groups were compared using analysis of covariance, with age as a covariate. Results: Dippers had lower (p < 0.001) nocturnal systolic and diastolic blood pressure than nondippers, and higher (p < 0.05) daytime diastolic blood pressure. Patients with nocturnal blood pressure decline had a markedly higher (p < 0.001) level of stress than nondippers. When the sample was divided according to the presence or absence of hypertension, only subjects with normalblood pressure showed nocturnal dipping associated with increased stressful life circumstances. Conclusions: Our findings indicate that dippers experience stressful life circumstances, both in terms of life events and chronic stress. Thissuggests that stress-reducing techniques may be particularly helpful in the setting of hypertension characterized by nighttime blood pressure dipping.

Comparison of the Effect of Carvedilol and Atenolol on Circadian Blood Pressure Profile in Patients with Essential Hypertension

SummaryWe conducted a single-blind, randomised block trial to assess the diurnal blood pressure (BP) profile after therapy with carvedilol, a nonselective β-blocker with additional α-blockade activity, and atenolol, a cardioselective β-blocker. 30 patients with mild to moderate essential hypertension were studied. After a 2-week placebo run-in period, they were randomly assigned to receive either atenolol 50 to 100mg once daily (15 patients) or carvedilol 25 to 50mg once daily (15 patients). 24-hour ambulatory blood pressure (ABP) monitoring was performed before and after 12 weeks of therapy, using a Kontron Micro AM 5600 device. The ABP readings were analysed with Fourier series with 4 harmonics. Atenolol and carvedilol significantly decreased office and ABP values versus placebo. Carvedilol: office systolic (SBP)/diastolic blood pressure (DBP) 131 ± 4/84 ± 7 vs 160 ± 6/101 ± 5; daytime SBP/DBP 125 ± 4/79 ± 6 vs 138 ±5/91 ±4; night-time SBP/DBP 115 ± 5/72 ± 5 vs 127 ± 3/80 ± 4. Atenolol: office SBP/DBP 133 ± 4/88 ± 3 vs 158 ± 5/102 ± 6; daytime SBP/DBP 124 ± 4/84 ± 3 vs 143 ± 3/97 ± 5; night-time SBP/DBP 117 ± 3/80 ± 6 vs 124 ± 5/88 ± 4. Heart rate was not significantly reduced by carvedilol. Carvedilol and atenolol showed a similar effect on BP profile; they did not modify the BP circadian rhythm. By contrast, both agents induced a significant decrease in the percentage of dippers (carvedilol from 73 to 33%, and atenolol from 60 to 40%), thus reducing the nocturnal BP dip.In conclusion, carvedilol and atenolol demonstrated similar effects on BP diurnal pattern in patients with essential hypertension. Moreover, the smaller reduction in heart rate by carvedilol may prevent severe bradycardia, an important and frequent adverse effect in patients treated with cardioselective β-blockers.