Hypertension
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The sixth Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure classifies blood pressure into stages on the basis of both systolic (SBP) and diastolic (DBP) blood pressure levels. When a disparity exists between SBP and DBP stages, patients are classified into the higher stage ("up-staged"). We evaluated the effect of disparate levels of SBP and DBP on blood pressure staging and eligibility for therapy. ⋯ SBP elevation out of proportion to DBP is common in middle-aged and older persons. SBP appears to play a greater role in the determination of JNC-VI blood pressure stage and eligibility for therapy. Given these results, combined with evidence from hypertension treatment trials, future guidelines might consider a greater role for SBP than for DBP in determining the presence of hypertension, risk of cardiovascular events, eligibility for therapy, and benefits of treatment.
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Both age and gender influence cardiovascular autonomic control, which in turn may influence the ability to withstand adverse cardiac events and respond to orthostatic stress. The purpose of this study was (1) to quantify age- and gender- related alterations in autonomic control of blood pressure (BP) and (2) to examine the impact of these autonomic alterations on BP response to orthostatic stress. We measured continuous BP and R-R intervals and vasoactive peptide levels in the supine and 60 degrees head-up tilt positions during paced respiration (0.25 Hz) in 89 carefully screened healthy subjects (41 men, 48 women, aged 20 to 83 years). ⋯ In elderly subjects, the tilt-induced increase in low-frequency BP power was also diminished (P=0.01), despite higher supine (P=0.02) and similar upright norepinephrine levels compared with younger subjects. Thus, healthy women have less sympathetic influence on BP and greater parasympathetic influence on R-R interval than men. Elderly subjects also have reduced sympathetic influence on BP, but this appears to be more consistent with a reduction in vasomotor sympathetic responsiveness.
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Comparative Study
Diastolic dysfunction and baroreflex sensitivity in hypertension.
The determinants of diastolic dysfunction in patients with systemic hypertension are not completely known. To evaluate the possible role of age, arterial blood pressure, and baroreflex heart rate response impairment in causing diastolic dysfunction, we studied 61 patients (42 male; mean+/-SD age, 43.9+/-12 years) with newly recognized and therefore previously untreated systemic hypertension. Diastolic dysfunction was evaluated by means of Doppler echocardiography (and diagnosed as such when the early to atrial peak velocity ratio corrected to heart rate was <1), arterial blood pressure by 24-hour ambulatory monitoring, and baroreflex heart rate response by means of the spectral technique (alpha index) during paced (0.27 Hz) and spontaneous breathing (in a supine position and during tilt). ⋯ The patients with diastolic dysfunction had significantly lower values for spectral baroreflex gain in the high-frequency band than those without (5.2+/-3 versus 8.4+/-5 ms/mm Hg during paced breathing, P<0.05; 7. 4+/-4 versus 13.3+/-7 ms/mm Hg in a supine position, P<0.05; 4.3+/-4 versus 5+/-2 ms/mm Hg during tilt, P
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Randomized Controlled Trial Comparative Study Clinical Trial
Raised cerebrovascular resistance in idiopathic orthostatic intolerance: evidence for sympathetic vasoconstriction.
Patients with idiopathic orthostatic intolerance (IOI) exhibit symptoms suggestive of cerebral hypoperfusion and an excessive decrease in cerebral blood flow associated with standing despite sustained systemic blood pressure. In 9 patients (8 women and 1 man aged 22 to 48 years) with IOI, we tested the hypothesis that volume loading (2000 cc normal saline) and alpha-adrenoreceptor agonism improve systemic hemodynamics and cerebral perfusion and that the decrease in cerebral blood flow with head-up tilt (HUT) could be attenuated by alpha-adrenoreceptor blockade with phentolamine. At 5 minutes of HUT, volume loading (-20+/-3.2 bpm) and phenylephrine (-18+/-3.4 bpm) significantly reduced upright heart rate compared with placebo; the effect was diminished at the end of HUT. ⋯ The decrease in blood flow velocity with HUT can be attenuated with interventions that improve systemic hemodynamics and therefore decrease reflex sympathetic activation. Moreover, alpha-adrenoreceptor blockade also blunts the decrease in cerebral blood flow with HUT but at the price of deteriorated systemic hemodynamics. These observations may suggest that in patients with IOI, excessive sympathetic activity contributes to the paradoxical decrease in cerebral blood flow with upright posture.