Diagnosis and treatment of supine hypertension in autonomic failure patients with orthostatic hypotension

Clonidine for the treatment of supine hypertension and pressure natriuresis in autonomic failure

Patients with autonomic failure are disabled by orthostatic hypotension, which can be worsened by the nighttime pressure natriuresis induced by associated supine hypertension. Several pharmacological agents are available that effectively reduce nighttime hypertension, but none of them prevent pressure natriuresis. Because hypertension of autonomic failure can be driven by residual sympathetic tone, we hypothesized that clonidine would be effective in reducing blood pressure (BP) and nocturnal natriuresis. Therefore, we determined the effect of placebo, 0.1 mg clonidine, and 0.1-mg/h nitroglycerin transdermal patch on supine BP, orthostatic hypotension, and pressure natriuresis in 23 patients with primary autonomic failure and supine hypertension. Medications were given at 8:00 PM, and BP was recorded every 2 hours for 12 hours. The maximal decrease in BP was seen 6 to 8 hours after drug administration and was similar to clonidine and nitroglycerin (-29+/-9 and -30+/-10 mm Hg, respectively), as was the average fall in BP throughout the night. However, only clonidine effectively reduced nocturnal natriuresis (-0.09 mmol/mg Cr; 95% CI, -0.13 to -0.04; P=0.004), but this was not associated with improvement in morning orthostatic hypotension because of a residual hypotensive effect. The decrease in BP induced by clonidine was modestly but significantly correlated with the magnitude of residual sympathetic tone determined in 10 subjects by the fall in BP induced by ganglionic blockade (r=0.66; P=0.043). These results are consistent with residual sympathetic tone contributing to supine hypertension in autonomic failure, which can be targeted with clonidine to decrease BP and nocturnal natriuresis.

Recommendations for blood pressure measurement in humans and experimental animals: part 1: blood pressure measurement in humans: a statement for professionals from the Subcommittee of Professional and Public Education of the American Heart Association Council on High Blood Pressure Research

Accurate measurement of blood pressure is essential to classify individuals, to ascertain blood pressure-related risk, and to guide management. The auscultatory technique with a trained observer and mercury sphygmomanometer continues to be the method of choice for measurement in the office, using the first and fifth phases of the Korotkoff sounds, including in pregnant women. The use of mercury is declining, and alternatives are needed. Aneroid devices are suitable, but they require frequent calibration. Hybrid devices that use electronic transducers instead of mercury have promise. The oscillometric method can be used for office measurement, but only devices independently validated according to standard protocols should be used, and individual calibration is recommended. They have the advantage of being able to take multiple measurements. Proper training of observers, positioning of the patient, and selection of cuff size are all essential. It is increasingly recognized that office measurements correlate poorly with blood pressure measured in other settings, and that they can be supplemented by self-measured readings taken with validated devices at home. There is increasing evidence that home readings predict cardiovascular events and are particularly useful for monitoring the effects of treatment. Twenty-four-hour ambulatory monitoring gives a better prediction of risk than office measurements and is useful for diagnosing white-coat hypertension. There is increasing evidence that a failure of blood pressure to fall during the night may be associated with increased risk. In obese patients and children, the use of an appropriate cuff size is of paramount importance.

Nonspecific dizziness: frequency of supine hypertension associated with hypotensive reactions on head-up tilt

The clinical syndrome of supine hypertension associated with orthostatic hypotension (OH) in given individuals is recognized by specialists, but is underdiagnosed in the community. The objective of this study was to assess supine hypertension associated with hypotensive reactions on head-up tilt (SH-HRT) among patients evaluated for nonspecific dizziness. Consecutive patients with nonspecific dizziness were studied with a 10-min supine 30-min head-up tilt test. Supine hypertension (SH) was diagnosed when supine systolic blood pressure (SBP) was > or = 140 mmHg and/or supine diastolic blood pressure (DBP) was > or = 90 mmHg. Hypotensive reactions on tilt (HRT) were diagnosed when SBP decreased by > or = 30 mmHg on tilt and/or DBP decreased by > or = 15 mmHg. Of 430 patients tested, 42 (9.8%) had SH-HRT. The median age was 67 years; 37 had a pretest diagnosis of hypertension, with treatment. The median supine BP was 162/90 mmHg; the median nadir BP on tilt was 118/78 mmHg. Four SH-HRT patterns were recognized: (I) SH with typical neurogenic OH (n = 6), (II) SH with vasovagal reaction on tilt (n = 4), (III) SH with sustained HRT (n = 28), and (IV) SH with mixed orthostatic-vasovagal reaction on tilt (n = 4). Dizziness on tilt occurred in 25% of patients category III (SH with sustained HRT), while appearing universally in other SH-HRT patterns. In conclusion, nonspecific dizziness may be the chief complaint in patients with SH-HRT, a disorder often unrecognized by clinicians. Different patterns of SH-HRT on HUTT may reflect different aberrations in cardiovascular homeostasis and may require differentiated management strategies.

Recommendations for Blood Pressure Measurement in Humans and Experimental Animals

Accurate measurement of blood pressure is essential to classify individuals, to ascertain blood pressure-related risk, and to guide management. The auscultatory technique with a trained observer and mercury sphygmomanometer continues to be the method of choice for measurement in the office, using the first and fifth phases of the Korotkoff sounds, including in pregnant women. The use of mercury is declining, and alternatives are needed. Aneroid devices are suitable, but they require frequent calibration. Hybrid devices that use electronic transducers instead of mercury have promise. The oscillometric method can be used for office measurement, but only devices independently validated according to standard protocols should be used, and individual calibration is recommended. They have the advantage of being able to take multiple measurements. Proper training of observers, positioning of the patient, and selection of cuff size are all essential. It is increasingly recognized that office measurements correlate poorly with blood pressure measured in other settings, and that they can be supplemented by self-measured readings taken with validated devices at home. There is increasing evidence that home readings predict cardiovascular events and are particularly useful for monitoring the effects of treatment. Twenty-four-hour ambulatory monitoring gives a better prediction of risk than office measurements and is useful for diagnosing white-coat hypertension. There is increasing evidence that a failure of blood pressure to fall during the night may be associated with increased risk. In obese patients and children, the use of an appropriate cuff size is of paramount importance.

Postural hypotension in hypertensive patients

BACKGROUND

The association between orthostatic hypotension and supine hypertension (Hypo-Hyper) has been reported in previous studies on selected populations. The present longitudinal study aimed to characterize the haemodynamic patterns, comorbidity, prognostic implications and eventual effect of therapy in patients with the Hypo-Hyper pattern.

METHODS

Ambulatory blood pressure monitoring (AMAP) and clinical evaluation were performed on 615 consecutive patients recruited from the Hypertension Clinics of five Italian Hospitals: 34 patents were identified as Hypo-Hyper, and underwent 10-month follow-up.

RESULTS

The incidence of the Hypo-Hyper pattern was 5.5% in the hypertensives studied. Hypo-Hyper was more frequent in the elderly (mean age 58 years), and the affected population exhibited different kinds of underlying pathologies. Multivariate analysis showed no association between antihypertensive treatment and Hypo-Hyper pattern. Patients with AMAP features of higher blood pressure values at night-time than at daytime displayed higher rates of myocardial hypertrophy and pacemaker implantation during the follow-up.

CONCLUSIONS

Although the study design did not aim to identify any pathophysiological mechanism for Hypo-Hyper pattern, these first data show that the Hypo-Hyper association is the effect of a particular subtype of hypertension, with significantly different prognostic implications.

Sympathetic control of the circulation in hypertension: lessons from autonomic disorders

PURPOSE OF THE REVIEW

Inappropriate sympathetic overactivity is consistently observed in patients with essential hypertension. The present review summarizes the recent advances that have been made in our understanding of the role of the sympathetic nervous system in hypertension.

RECENT FINDINGS

Studies in patients with autonomic disorders underscore the role of the sympathetic nervous system in the long-term maintenance of hypertension. Abnormalities in the afferent limb of the sympathetic nervous system, in the regulation of central neurons where sympathetic outflow originates, and in the modulation of efferent sympathetic function, can all produce autonomic disorders that are associated with hypertension. More subtle dysfunctions in any of these components have been described in essential hypertension and can contribute to its pathogenesis. These include impaired buffering capacity of arterial baroreflexes, increased central sympathetic outflow, and enhanced norepinephrine release (or decrease reuptake) from sympathetic nerve terminals. Whether genetic polymorphisms of adrenoreceptors are associated with essential hypertension is an area of active research.

SUMMARY

Increased sympathetic activity can contribute to sustained hypertension not only because of its hemodynamic effects (increased cardiac output and vascular resistance), but also by altering renal and water handling by the kidney, and by inducing cardiac and vascular remodeling. Antihypertensive agents that directly or indirectly target this sympathetic overactivity may be particularly useful in long-term treatment of essential hypertension.