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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Frank-Starling relationship of hearts from adult spontaneously hypertensive rats (SHR, Okamoto 1969), representing the established phase of hypertension, and of young SHR, representing the initial phase of hypertension, was investigated by using the isolated working heart preparation. In the "normal" diastolic pressure range (5 to 10 cm H2O), the left ventricle of both SHR groups displayed significantly reduced stroke volumes compared with hearts of normotensive controls (NCR); the degree of reduction being proportional to the left ventricular hypertrophy. This is suggested to be due to a reduced left ventricular diastolic compliance in SHR, as indicated by direct measurements of ventricular wall thickness and end-diastolic volumes in arrested hearts exposed to different end-diastolic filling pressures. Such a progressive shift of the Frank-Starling relationship to the right with duration of hypertension could, in combination with the gradual development of "structural autoregulation" of the precapillary resistance vessels, constitute dominating factors in shifting the hemodynamic situation in labile hypertension into that characterizing the established, or "fixed", state of hypertension.
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PMID:Consequences of myocardial structural adaptation on left ventricular compliance and the Frank-Starling relationship in spontaneously hypertensive rats. 12 25

The hypertensive encephalopathy is a syndrome consisting of a sudden elevation of arterial pressure usually preceded by severe headache and followed by convulsions, coma or a variety of transitory cerebral phenomena. The syndrome may complicate acute glomerulonephritis, toxemia of pregnancy and essential or malignant hypertension. Two syndromes must be differentiated from true hypertensive encephalopathy: 1. acute anxiety state with labile hypertension and 2. acute pulmonary edema due to hypertensive heart disease. At least in patients with acute anxiety states, the use of antihypertensive agents is usually not indicated. Since encephalopathy is always accompanied by increased vascular resistance and since clinical experience has demonstrated clearing of the sensorium, cessation of convulsions and release of vasoconstriction following reduction of blood pressure, the primary aim of therapy should be prompt lowering of arterial pressure. The two agents of choice are diazoxide and sodium nitroprusside. Stroke is differentiated from encephalopathy by the persistence of lateralizing signs. The aggressiveness of antihypertensive therapy in this situation depends on the severity of the hypertensive process. Rapid reduction of blood pressure is indicated in patients found to have accelerated hypertension while a more gradual lowering of pressure appears warranted for patients with chronic arterial hypertension and evidence of generalized arteriosclerosis.
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PMID:Management of hypertensive encephalopathy. 72 Oct 56

Hypertension in spontaneously hypertensive rats (SHR) develops initially without any obvious organic lesions, and mainly with hemodynamic alteration due to increased peripheral vascular resistance. It is then followed later by various cardiovascular complications such as stroke. These facts indicate that this spontaneous hypertension is very similar to essential hypertension in man. Studies on the pathogenic mechanisms of spontaneous hypertension up to the present have revealed the following points. (1) This hypertension is genetically transmitted to the offspring in an additive mode by a relatively small number of major genes; (2) Environmental factors such as stress and salt-loading accelerate the hypertension; (3) Parabiosis between SHR and normotensive rats offered no positive evidence indicating the involvement of any strong humoral factors; (4) Assays on adrenal and thyroid hormones have suggested that this hypertension is not a simple endocrine hypertension; (5) The destruction of the central nervous system or sympathectomy on blood pressure or peripheral vascular resistance, as well as the recording of spontaneous sympathetic discharge, etc. have indicated the positive involvement of the autonomic nervous system in the development of this hypertension; (6) Changes in the enzyme activities of the central nervous system and in the central responses to various candidates of central neurotransmitters suggested that 'noradrenergic inhibitory mechanisms for blood pressure regulation in the brainstem' (Yamori, Lovenberg and Sjoerdsma, 1970) might be insufficient and result in the initial enhancement of peripheral vasomotor tone causing labile hypertension; (7) Noradrenalin turnover study of the heart and hindlimb perfusion experiments indicated that the neural factor was mainly involved in the development or the early stage of hypertension; this finding was further supported by the increased noradrenalin level or dopamine-beta-hydroxylase activity in the blood; (8) Histometrical studies indicated that the structural component of the peripheral vascular resistance stabilized the hypertension; (9) The initial neurogenic factors and successive involvement of nonneurogenic factors are relayed by the acceleration of protein metabolism of the vascular wall ('adaptive metabolic change', Yamori, 1974). This acceleration is commonly detected by amino acid incorporation study in both spontaneous and other experimental hypertension; (10) Increased lysine incorporation into the noncollagenous protein of the mesenteric arteries detected in the prehypertensive SHR was experimentally confirmed to be influenced by neural innervation. This confirmation indicated the importance of such a trophic effect of the nervous system on the structural alteration of blood vessels in the development of hypertension (neurovascular linkage, Yamori, 1975)...
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PMID:Pathogenesis of spontaneous hypertension as a model for essential hypertension. 87 Jul 22

In a birth cohort of children in the Dunedin Multidisciplinary Health and Development Study in New Zealand, resting blood pressures were recorded biennially five times from age 7 to 15 years. Using previously described methods, we examined the level, trend, and variability of blood pressures in those children with at least three readings. The level, trend, and variability of height, weight, and body mass index were compared among six separate groups of children. Two groups were categorized on the basis of high systolic pressure levels, one with low variability and the other with high variability, which was thought to resemble adult labile hypertension. Two additional groups were categorized on the basis of increasing and decreasing blood pressure trends; the fifth group had consistently low blood pressures, and the sixth group consisted of the remaining children. There were significant differences among the groups for the level of all the physical measurements and for the trend of body mass index. No significant differences were found among the groups for gender or socioeconomic status. A parental history of high blood pressure, stroke, or heart attack was significantly more common in the first two groups.
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PMID:Blood pressure level, trend, and variability in Dunedin children. An 8-year study of a single birth cohort. 222 85

Systolic time interval (STI) analysis is a commonly employed noninvasive technique for evaluating myocardial function. It requires simultaneous recording of an electrocardiogram, phonocardiogram, and the carotid pulse contour, from which left ventricular ejection time is measured. The carotid pulse contour may be difficult to record when there is subject movement, such as with exercise or other stresses utilized in aerospace medical research. Impedance cardiography is a relatively new noninvasive technique for measuring stroke volume. It also provides a measure of systolic ejection time without the necessity of recording a carotid pulse contour. The purpose of this study was to determine the correlation between left ventricular ejection time (LVET) determined from conventional STI analysis and systolic ejection time (T) obtained with impedance cardiography. The electrocardiogram, phonocardiogram, carotid pulse contour, and impedance cardiogram were monitored simultaneously in 17 male subjects 39-63 years of age (6 normotensive, 7 with established hypertension, and 4 with labile hypertension). Subjects were monitored at seated rest and during submaximal and maximal cycle ergometer exercise. Beat-by-beat analysis revealed high intrasubject correlations between LVET and T for each subject during all three activity levels. Correlations between LVET and T for the combined group of 17 subjects were: rest r = 0.990, submaximal exercise r = 0.976, maximal exercise r = 0.986; p less than 0.01. These results indicate impedance cardiography can be used in the determination of STIs for the evaluation of ventricular function, as well as for the noninvasive determination of stroke volume and cardiac output.
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PMID:Correlations between ejection times measured from the carotid pulse contour and the impedance cardiogram. 665 10

Because the arterial baroreceptor reflex function that modulates the variability of blood pressure decline with advancing age, blood pressure in the elderly is more variable than in young patients. Recent advances in ambulatory blood pressure monitoring devices clarified the changes in the blood pressures in daily life which had been never observed by the office blood pressure measurement. 1. White coat hypertension: Temporary elevation of blood pressure in the clinic is referred as a white coat hypertension and there is much recent evidence indicating that it is common in the elderly. Our recent data indicated that left ventricular mass in patients with white coat hypertension is higher than that in the normotensive groups, although it is lower than that in the true persistent hypertensive group. This suggests that white coat hypertension is never innocent and should be treated by a mild antihypertensive drug. 2. Morning surge: Many reports indicate that cardiovascular events occur more frequently in the early morning, suggesting a morning rise in blood pressure might be associated with this catastrophe. Using an activetrace that assesses physical activity objectively, we recently clarified that morning surge can be divided into two types. One is morning rise which begins in accordance with awakening and arising. The other is a rise during sleep before awakening. 3. Although blood pressure rises during the daytime and decreases at nighttime in healthy individuals, recent reports indicate that there are many conditions in which blood pressure does not fall at night. Individuals with this condition have been called non-dippers and tend to be associated with hypertensive target-organ damage such as silent stroke or Binswanger's dementia.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Ambulatory blood pressure in the elderly with hypertension]. 769 38

Hemodynamic alterations associated with the blood pressure response in subjects with white coat hypertension may provide insight into the pathophysiologic mechanisms of this condition. Systemic arterial hemodynamics were investigated with a recently validated method based on noninvasive estimates of aortic root pressure and flow in 28 subjects with white coat hypertension (diastolic pressure > or = 90 mm Hg measured by the general practitioner [GP arterial pressure] and ambulatory daytime pressures < 140/90 mm Hg), in 23 subjects with previously untreated, ambulatory hypertension (GP diastolic pressure > or = 90 and < 115 mm Hg and ambulatory daytime diastolic pressure > or = 90 mm Hg), and in 32 normotensive subjects. The groups did not differ significantly concerning age, gender, body surface area, heart rate, stroke index and cardiac index, but total peripheral resistance index was increased and total arterial compliance reduced in the white coat group and the hypertensive group compared to the normotensive group. The subjects in the white coat group with a systolic arterial pressure during echocardiography that was > 5 mm Hg higher than the ambulatory daytime systolic pressure (n = 19) had increased cardiac index, increased total peripheral resistance, and decreased total arterial compliance compared to the normotensive group. The subjects in this group with a hemodynamic pattern characterized by a high ratio of cardiac index/peripheral vascular resistance were significantly younger than the subjects with the opposite pattern. Thus, the blood pressure increase in subjects with white coat hypertension is associated with increased cardiac output, increased peripheral vascular resistance, and reduced total arterial compliance, but the hemodynamic pattern may be influenced by age.
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PMID:Hemodynamics in white coat hypertension compared to ambulatory hypertension and normotension. 893 34

Until recently, there has been little evidence substantiating the belief that mental stress provokes myocardial infarction and stroke, and aggravates atherosclerosis. However, recent advances in methodology for demonstrating effects of stress are now beginning to build a foundation of evidence that supports those beliefs. In monkeys, social stress doubles coronary atherosclerosis, and increases coronary spasm, and treatment with oestrogen, which improves endothelial function, reduces coronary spasm in relation to stress. In human beings, mental stress provokes myocardial ischaemia, and haemodynamic responses to mental stress predict progression of left ventricular enlargement, and progression of carotid atherosclerosis. These findings suggest that it may not be safe to withhold treatment of high office pressures in patients with white coat hypertension. There is now some evidence that stress management in the form of individualized cognitive behavioural interventions reduces blood pressure. Further work is needed to determine whether it is safe to withhold treatment in white-coat syndrome, and whether stress management can reduce atherosclerosis and ischaemic events.
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PMID:Neurocardiology. Stress and atherosclerosis. 948 93

The authors showed, in a spin-off study of SYST-EUR, that 24% of subjects with isolated systolic hypertension on conventional measurement were not hypertensive during ambulatory blood pressure monitoring. Moreover, in white coat hypertension, treatment had no effect either on the electrical signs of left ventricular hypertrophy or on the incidence of clinical events (cerebrovascular accident and global cardiovascular complications), contrary to what is observed in permanent systolic hypertension. These results raise question as to the diagnosis and treatment of isolated systolic hypertension in the elderly and prompt to a larger usage (if not systematic) of ambulatory blood pressure monitoring in this context. The importance of systolic blood pressure and pulsed pressure For different reasons, diastolic blood pressure was thought to be of greater prognostic significance, as the very large majority of clinical trials recruited on the basis of the value of their diastolic blood pressure alone demonstrate. In recent years, the importance of systolic blood pressure has been underlined in many studies and 3 trials have shown the unquestionable benefits of treatment of isolated hypertension. It would also appear that the pulse pressure, which reflects arterial compliance, has considerable prognostic value. In the absence of established manometric criteria and mostly of therapeutic trials, the practical use of the pulse pressure remains questionable. The interruption of the doxazosin arm of the ALLHAT trial The ALLHAT (Antihypertensive and Lipid Lowering Treatment to Prevent Heart Attack Trial) study showed a doubling of the morbidity from cardiac failure, a 19% excess of cerebrovascular events and 16% of angina pectoris in subjects treated with doxazosin compared with those treated with chlorthalidone. The differences in blood pressure with treatment were minimal and, a priori, unable to explain these results. Beyond the fact that alphablockers cannot be considered as first-line antihypertensive therapy, without doubt, the affirmation that lowering the blood pressure provides the same benefit irrespective of the antihypertensive agent used, probably needs to be reviewed.
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PMID:[The best in 2000 on arterial hypertension]. 1126 Aug 42

The prevalence of hypertension in persons aged 80 years or older is about 70%. Recent studies in this population show the benefits of antihypertensive therapy, especially for stroke prevention. Accurate determination of blood pressure requires the use of ambulatory measurement methods or self-measurement at home because the frequency of "white coat" hypertension increases with age. It is essential to distinguish patients with sustained hypertension, who need antihypertensive drugs, from those with white coat hypertension, for whom treatment is not justified and may be dangerous because of the risk of hypotension. The objective of antihypertensive treatment is to decrease blood pressure to less than 140/90 mmHg for those aged 60 to 80 years and to decrease systolic pressure to less than 150 mmHg in those older than 80 years, without orthostatic hypotension. Any class of antihypertensive drugs can be used to start treatment, although in the absence of specific indications due to concomitant diseases, thiazide diuretics or calcium channel blockers are preferred for initial treatment. Most often, very elderly hypertensive patients will require two antihypertensive drugs for adequate blood pressure control. Generally their regimen should not include more than 3 antihypertensive drugs (including a thiazide diuretic).
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PMID:[Management of hypertension in the very elderly]. 1678 71


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