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The 24 hour relation between R-R interval and diastolic blood pressure measured by ambulatory blood pressure monitoring.
No full textTHE 24 HOURS RELATION BETWEEN RR INTERVAL AND DIASTOLIC BLOOD PRESSURE CHANGES ±MEASURED BY AMBULATORY BLOOD PRESSURE MONITORING
G. Recordati, A. Zanchetti. Centro Fisiologia Clinica ed Ipertensione. Universita’ degli Studi ed Ospedare Maggiore. Milano. Italy
Background: The day and night circadian rhythm is accompanied by reciprocal changes in vagal and sympathetic dominance which may be quantified by measuring the R-R interval (R-R) and diastolic blood pressure (DBP) changes relation with ambulatory blood pressure monitoring (ABPM). Methods: ABPM was performed using Spacelabs monitors in 60 healthy young subjects (30 females and 30 males aged 21.8±1.0) with readings every 15 min (day) and 20 min (night). The collected variables were copied to a software program (Diadem. National Instruments) and R-R values obtained by dividing 60.000 by heart rate in beats/min. The following measurements were made: 1) night and day means ± SD: 2) night less day R-R (Δy, msec) and DBP (Δx. mmHg) differences and Δy/Δx ratios (ms/mmHg): 3) percent :Δy, Δx changes over day mean values and their ratio and 4) slope (b _24h) and r coefficient (r_24h) of the regression of R-R over DBP 24 hours values. Results: With respect to day. night was characterized by lengthenirg of R-R and lowering of DSP values in all subjects. The R-R and DBP day and night means ± SD. the night less day differences and the Δy/Δx ratios, both actual and percent. and the b_24h were different and characteristic for each subject. The r _24h reached statistical significance in all subjects Subjects were classified according to their proportionality ratios between R-R and DBP changes: two subjects had a Δy/Δx ratio below -5, 18 between -5 and -10, 28 between -10 and -20 and 12 above -20 ms/mmHg (range: -41.1 to -4.6. mean -14.6 ms/mmHg). The percent Δy/Δx ratio ranged from -32 to -0.5, mean -1.3 and the slope, b_24h, ranged from -14.28 to -3.14, mean -9.12 ms/mmHg. Conclusions: Results indicate that the ABPM may allow to quantify the individual's day—night autonomic reciprocity and that the subjects with steeper proportionality ratios have a higher 24h period vagal tone. This novel approach may thus be helpful to study the autonomic balance in several patients groups and the individual effects of different pharmacologjcal treatments
The 24 hours relation between R-R interval and diastolic blood pressure changes measured by ambulatory blood pressure monitoring
No full textEvaluation of the 24 hours sympatho-vagal balance by the phase-space distribution of arterial blood pressure monitoring (ABPM) values
No full textEffects of a reversible 'nephrectomy' on renal sympathetic activity and blood pressure in the rat : evidence for an acute angiotensin-mediated hypertension
No full textObjective To verify whether the normal kidney exerts a supportive, facilitatory action an renal sympathetic nerve activity (RSNA), the effects of unilateral and bilateral nephrectomy on RSNA have been studied.
Methods The RSNA, rectal temperature (T), rate of breathing (RB), arterial brood pressure (BP) and heart rate (HR) were continuously recorded in three groups of pentobarbital anaesthetized, spontaneously breathing Sprague-Dawley rats: group 1 (n = 5): both kidneys intact; group 2 (n = 5): left surgical nephrectomy; group 3 (n = 5): left surgical nephrectomy and functional exclusion of the right kidney (functional right nephrectomy, FRN), produced by a tight ligature of the renal hilum which was maintained for 3 h. In a fourth group (n = 7), in which nerve activity was not recorded, reopening of the right renal hilum was preceded or followed by intravenous administration of captopril (3 mg/kg).
Results In groups 1 and 2 RSNA increased from 22.3 +/- 2.1 to 122.9 +/- 13.6 and from 26.7 +/- 1,2 to 93.2 +/- 14.0 impulses/s (mean +/- SEM), respectively, without concomitant changes in cardiovascular parameters. In group 3 RSNA decreased from 39.1 +/- 3.1 to 13.7 +/- 2.6 impulses/s during the 3 h of FRN. In group 3 the reopening of the right renal hilum was followed by a marked increase in BP and HR that was prevented or reversed by intravenous captopril in rats of group 4.
Conclusions The decrease in RSNA observed in rats during bilateral nephrectomy, in contrast to the increase observed in rats with one or both kidneys intact, suggests that the kidney as a whole exerts a supportive role on sympathetic nerve activity. The hypertension and tachycardia that follows the reopening of the right kidney hilum appears to be caused by the generation of endogenous angiotensin II; this is the first evidence of an acute angiotensin-mediated renal hypertension
Hypertensive myocardial fibrosis.
No full textA variety of cardiac structural and functional changes,
such as increased left ventricular mass (LVM), left
atrial and aortic root enlargement, LV dysfunction,
impairment of coronary reserve and prolonged ven-
tricular repolarization, have been described in patients
with long-standing arterial hypertension [1,2].
However, subtle modifications in LV structure and
geometry may occur also in the early phases of the
natural history of essential hypertension [3]. Among
these manifestations of target organ damage, most
attention has been devoted to LV hypertrophy (LVH),
because the prevalence of this phenotype is relatively
high and is associated with an increased risk of
cardiovascular morbidity and mortality [4,5]
Monitoraggio della pressione arteriosa in pazienti "Extreme Dippers" e sua rappresentazione in spazio-di-fase.
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