Drug treatment of orthostatic hypotension and vasovagal syncope

5-HT is a potent relaxant in rat superior mesenteric veins

Serotonin (5-HT, 5-hydroxytryptamine) reduces blood pressure of the conscious rat when administered chronically (1 week). 5-HT does not directly relax isolated arteries, and microsphere experiments in 5-HT-infused rats suggested that 5-HT increased flow to the splanchnic bed. We hypothesized that 5-HT increased splanchnic flow because of direct venous relaxation; our focus was thus on the superior mesenteric vein (SMV) as an important vein in splanchnic circulation. Real-time RT-PCR, immunohistochemistry and Western analyses supported the predominant expression of the 5-HT_2B and 5-HT₇ receptor in the SMV. The SMV was mounted in tissue baths for measurement of isometric contraction. 5-HT caused a concentration-dependent relaxation of the endothelin-1 (ET-1)-contracted vein. The threshold of 5-HT-induced venous relaxation was significantly lower than for 5-HT-induced venous contraction (∼2 vs. 700 nmol/L, respectively). A series of serotonergic agonists established in their use of receptor characterization was tested, and the following rank order of potency found for agonist-induced relaxation (receptor selectivity): 5-CT (5-HT₁/5-HT₇)>5-HT = LP-44 (5-HT₇)>PNU109291 (5-HT_1D) = BW723C86 (5-HT_2B). 8-OH-DPAT (5-HT_1A/7), CP93129 (5-HT_1B), mCPBG (5-HT_3/4), AS19 (5-HT₇) and TCB-2 (5-HT_2A) did not relax the isolated vein. Consistent with these findings, two different 5-HT₇ receptor antagonists SB 269970 and LY215840 but not the 5-HT_2B receptor antagonist LY272015 nor the nitric oxide synthase inhibitor LNNA abolished 5-CT-induced relaxation of the isolated SMV. 5-CT (1 μg kg⁻¹ min⁻¹, sc) also reduced blood pressure over 7 days. These findings suggest that 5-HT directly relaxes the SMV primarily through activation of the 5-HT₇ receptor.

Neuroprotection and neurodegeneration in Alzheimer's disease: role of cardiovascular disease risk factors, implications for dementia rates, and prevention with aerobic exercise in african americans

Prevalence of Alzheimer's disease (AD) will reach epidemic proportions in the United States and worldwide in the coming decades, and with substantially higher rates in African Americans (AAs) than in Whites. Older age, family history, low levels of education, and ɛ4 allele of the apolipoprotein E (APOE) gene are recognized risk factors for the neurodegeneration in AD and related disorders. In AAs, the contributions of APOE gene to AD risk continue to engender a considerable debate. In addition to the established role of cardiovascular disease (CVD) risk in vascular dementia, it is now believed that CVD risk and its endophenotype may directly comediate AD phenotype. Given the pleiotropic effects of APOE on CVD and AD risks, the higher rates of CVD risks in AAs than in Whites, it is likely that CVD risks contribute to the disproportionately higher rates of AD in AAs. Though the advantageous effects of aerobic exercise on cognition is increasingly recognized, this evidence is hardly definitive, and data on AAs is lacking. In this paper, we will discuss the roles of CVD risk factors in the development of AD and related dementias, the susceptibility of these risk factors to physiologic adaptation, and fitness-related improvements in cognitive function. Its relevance to AD prevention in AAs is emphasized.

Comprehensive geriatric assessment of elderly highlanders in Qinghai, China II: the association of polycythemia with lifestyle-related diseases among the three ethnicities

AIM

The objective of this study is to disclose the association of polycythemia with lifestyle-related diseases (hypertension, obesity and glucose intolerance) among the three ethnicities in Qinghai, China.

METHODS

The subjects were 393 elderly people (247 Han, 97 Tibetan and 49 Mongolian) aged 60 years and more living in Qinghai (3000 m a.s.l.) in China. The associated factors with polycythemia were analyzed in the subjects. Excessive polycythemia was defined as hemoglobin concentration over 20 mg/dL.

RESULTS

Polycythemia was associated with men, hypoxemia, obesity and high diastolic blood pressure (DBP) in the elderly in Qinghai. Male sex was associated with polycythemia in all ethnicities. Obesity was associated with Han and Tibetan men. Glucose intolerance and activities of daily living were not directly associated with polycythemia after adjustment for sex. There were 7.9% with excessive polycythemia. Independently-associated factors for excessive polycythemia were male sex, body mass index of 25 or more, SpO(2) of less than 85%, DBP of 85 mmHg or more and Han ethnicity (vs Tibetan) by multiple logistic regression.

CONCLUSION

There was a close association of polycythemia with diastolic hypertension and obesity in lifestyle-related diseases in high-altitude elderly people. Han people had a higher hemoglobin concentration after adjustment of lifestyle-related diseases compared with Tibetan people. The difference of hemoglobin concentration may be due to Tibetans undergoing a much longer period of adaptation than Han people. Further study is needed to disclose the association between the difference of hypoxic adaptation, lifestyle-related diseases and chronic mountain sickness for their prevention.

Dizziness in an older community dwelling population: a multifactorial syndrome

OBJECTIVES

The aim of this study was to determine the prevalence and related predictors of dizziness in a sample of community-dwelling people 65 years of age and older living in a metropolitan area in Germany.

DESIGN

Prospective cohort study.

SETTING

Interdisciplinary Centre of Gerontology at the University of Erlangen- Nuremberg, Germany.

PARTICIPANTS

6000 people aged 65 years and older recruited and randomized from the registration office, 1801 were fully evaluated at baseline and were re-evaluated in a prospective follow-up two years later. A full data set was obtained for 620 participants, of which 297 (47.9%) were females. Mean age was 73.45 +/- 6.05. 200 participants (32.4%) were 65-69 years, 315 (51%) were 70-79 years, 92 (14.9%) 80-89 years and 11 (1.8%) 90 years and older.

MEASUREMENTS

Demographic, medical, functional and psychological factors were measured by a standardised questionnaire in 2004. In a follow-up survey participants were reevaluated in a prospective design two years later (2006), including a dizziness questionnaire, containing frequency, duration, space of dizziness and releasing positions and activities.

RESULTS

At the second measurement 181 persons (29.2%) reported dizziness in the last 6 months. Dizziness was age dependent, with a prevalence of 27% in participants aged 70 years and younger, up to 54% in the group of 90 years and older. 96 (68.2%) persons reported daily or weekly dizziness. 46 (27.9%) participants reported multiple sensations of dizziness. In 108 (59.7) persons dizziness was released by multiple positions or activities. The main predictors of dizziness were age, female gender, cardiovascular disease, osteoporosis, depression, sleep disorder, disturbance of memory, shortsightedness (defined by glasses), incontinence, 3 and more medical conditions, 4 and more medications, poor health status, falls and mobility problems. We found similar risk factors for dizziness and falls.

CONCLUSION

Dizziness is a very common symptom in older community dwelling persons. Comorbidity, poor health status and mobility problems are strong medical predictors; age and female gender and decline in mobility are important predictors as well. Our study suggests, that dizziness in older age is often caused by multifactorial medical and functional conditions. Gait disorders and mobility problems also seem to play an important role in dizziness among older people. Therefore, interventions in dizziness should be developed in a multifactorial way. We suggest, that the interventions to be tested first, should be those that have been previously successful in older persons with gait disorders and falls.

Pathophysiology, diagnosis, and treatment of orthostatic hypotension and vasovagal syncope

Orthostatic hypotension (OH) occurs in 0.5% of individuals and as many as 7-17% of patients in acute care settings. Moreover, OH may be more prevalent in the elderly due to the increased use of vasoactive medications and the concomitant decrease in physiologic function, such as baroreceptor sensitivity. OH may result in the genesis of a presyncopal state or result in syncope. OH is defined as a reduction of systolic blood pressure (SBP) of at least 20 mm Hg or diastolic blood pressure (DBP) of at least 10 mm Hg within 3 minutes of standing. A review of symptoms, and measurement of supine and standing BP with appropriate clinical tests should narrow the differential diagnosis and the cause of OH. The fall in BP seen in OH results from the inability of the autonomic nervous system (ANS) to achieve adequate venous return and appropriate vasoconstriction sufficient to maintain BP. An evaluation of patients with OH should consider hypovolemia, removal of offending medications, primary autonomic disorders, secondary autonomic disorders, and vasovagal syncope, the most common cause of syncope. Although further research is necessary to rectify the disease process responsible for OH, patients suffering from this disorder can effectively be treated with a combination of nonpharmacologic treatment, pharmacologic treatment, and patient education. Agents such as fludrocortisone, midodrine, and selective serotonin reuptake inhibitors have shown promising results. Treatment for recurrent vasovagal syncope includes increased salt and water intake and various drug treatments, most of which are still under investigation.