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 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cardiac sympathetic function was assessed by measuring the coronary sinus overflow of noradrenaline and dopamine at rest and during supine exercise in eight patients with high degree atrioventricular block treated with dual chamber pacemakers (DDD). Patients exercised (30-60 W) during both ventricular inhibited (VVI) and atrial synchronous (VAT) pacing. During exercise cardiac output increased less markedly in the VVI mode than in the VAT mode. The cardiac output response was entirely stroke volume dependent in the VVI mode and mainly heart rate dependent in the VAT mode. Coronary sinus noradrenaline concentrations were higher in the VVI mode at rest and during exercise. Noradrenaline overflow from the heart was enhanced during VVI pacing and increased from about 100 pmol/min (17 ng/min) at rest to 1087 pmol/min during exercise (60 W) in the VVI mode and 545 pmol/min in the VAT mode. Dopamine overflow from the heart was less than 5 pmol/at rest but increased 2-5 fold during exercise. Also arterial concentrations of catecholamine increased more during exercise in the VVI mode, but the differences between pacing modes were less pronounced. Circulating adrenaline seems to be of little importance for cardiac function under these conditions; in healthy individuals the arterial concentrations of adrenaline attained in this study have small effects. Cardiac noradrenaline overflow correlated with pulmonary capillary venous pressures and atrial rates in both pacing modes, indicating a relation between cardiac sympathetic activity and cardiac function. Enhanced cardiac release of noradrenaline may increase cardiac contractility and thereby partially compensate for the lack of heart rate responsiveness to exercise during VVI pacing.
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PMID:A comparison of sympathoadrenal activity and cardiac performance at rest and during exercise in patients with ventricular demand or atrial synchronous pacing. 317 37

The role of certain resistance vessel characteristics in the etiology of hypertension has been investigated using F2-generation hypertensive/normotensive rats. The F2 populations were bred from spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY) as well as from stroke-prone SHR (SHRSP) and outbred Wistar-Kyoto rats (WKYO), and are denoted SHR/WKY and SHRSP/WKYO, respectively. Mesenteric resistance vessels (lumen diameter ca 200 micron) were taken from rats in the highest and lowest blood pressure quartiles of 14-week SHR/WKY and 18-week SHRSP/WKYO, as well as from 15-week pure SHR and WKY and from 18-week pure SHRSP and WKYO. The vessels were mounted on a myograph for determination of their structural and contractile characteristics. The structure of the vessels, as expressed for example by their media : lumen ratio, was greatest in the vessels from the SHR and the SHRSP compared to those from the WKY and WKYO. Increased structure was seen in the vessels from the rats in the high blood pressure quartiles of each group of F2 populations, compared to the vessels from the rats in the low blood pressure quartiles, although in the SHR/WKY the difference was smaller than expected if structure were a major determinant of blood pressure. Vascular sensitivity to calcium and the effect of cocaine on noradrenaline sensitivity were increased in the vessels from the SHR and SHRSP, but were the same in the high and low blood pressure quartiles of the F2 populations.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Resistance vessel structure and function in the etiology of hypertension studied in F2-generation hypertensive-normotensive rats. 318 71

The carotid sinus baroreceptors were stimulated in 34 patients with heart failure (NYHA II-III) and sinus rhythm. We found that reflex bradycardia is caused by a selective increase in parasympathetic activity and the increase in cycle length depends on the degree of baroreceptor stimulation, therefore a regression line could be calculated for each patient. The slopes of these regression lines were used as an index of baroreflex sensitivity. Initial heart rate, age, stroke volume index, and plasma-noradrenaline concentration correlated with baroreflex sensitivity. However, according to multiple regression analysis (r = 0.64, p less than 0.001), only age correlated negatively (p less than 0.05), and the stroke volume index correlated positively (p less than 0.001) with baroreflex sensitivity: the lower the stroke volume index the smaller the baroreflex sensitivity. This indicates that reflex increases in parasympathetic activity depend on the degree of heart failure.
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PMID:[Reflex regulation of heart rate in patients with heart failure]. 319 76

The role of the sodium-calcium (Na-Ca) exchange in vascular smooth muscle contraction was examined in tail artery rings isolated from stroke-prone spontaneously hypertensive rats (SHRSP) and in normotensive Wistar-Kyoto rats (WKY). The rings were repeatedly stimulated with noradrenaline (1 microM) in physiological salt solution (Na = 130 mM), until two successive contractions were of the same magnitude. The rings were then placed in physiological salt solution with reduced sodium concentrations (65 mM or 0 mM, replaced isosmotically with sucrose), and the noradrenaline stimulations continued. In WKY rings, the reduction of sodium concentration produced an increase in the response to noradrenaline, which was significant in sodium-free physiological salt solution. In SHRSP rings, however, the same reductions in sodium concentration produced significantly less potentiation of the noradrenaline contraction, even in sodium-free physiological salt solution. We conclude that (1) in WKY, the reduced and reversed activity of the Na-Ca exchange produced by the reductions in sodium concentration makes more calcium available for contraction when the smooth muscle is stimulated with noradrenaline; and (2) the failure of sodium reductions to produce a normal potentiation of the response to noradrenaline in SHRSP indicates a depressed activity of the Na-Ca exchange in this tissue.
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PMID:Sodium-calcium exchange in vascular smooth muscle of Wistar-Kyoto and stroke-prone spontaneously hypertensive rats. 324 Nov 92

The haemorheological disturbances observed in primary hypertension arise mainly from haemoconcentration, which leads to an elevation of blood and plasma viscosity and increased aggregation of red blood cells (RBCs). We evaluated the rheological properties of blood and central haemodynamic indices in 13 men with untreated primary hypertension (WHO stage I and II), during a baseline period and after intravenous infusion of 1000 ml of 0.9% NaCl (within 12-15 min). The rheological properties studied were: whole blood viscosity (WBV), plasma viscosity (PV), haematocrit (HCT) and plasma fibrinogen concentration (PF). The central haemodynamic indices were: mean intra-arterial blood pressure (MAP), central venous pressure (CVP), cardiac index (CI), stroke volume index (SVI), total peripheral resistance index (TPRI) and the vascular hindrance index (VHI). Plasma renin activity (PRA) and plasma noradrenaline concentration (P-NA) were also measured. Volume expansion with saline caused haemodilution as expressed by a fall in HCT (P less than 0.001), WBV (P less than 0.001) and PV (P less than 0.01). At the same time, CVP, MAP and VHI increased (P less than 0.05) while PRA decreased (P less than 0.05) and P-NA remained unchanged. Mean values of the cardiac index (CI) and stroke volume index (SVI) did not change significantly. We did not observe any significant relationship between haemodynamic and haemorheological parameters, during baseline or between their respective changes after the infusion. The results indicate that although hypervolaemic haemodilution produced by saline infusion in hypertensive patients may improve blood flow properties (HCT, WBV, PV), blood pressure (BP) is not reduced; rather the converse is true. The reduction in HCT and hence the improved blood rheology, did not affect calculated vascular resistance. Thus, correction of WBV does not acutely normalize BP in primary hypertension.
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PMID:Haemodynamic and haemorheological effects of hypervolaemic haemodilution in men with primary hypertension. 330 38

To test the effect of a high dietary calcium intake on blood pressure, we fed stroke-prone spontaneously hypertensive (SHR-SP) and Wistar-Kyoto rats (WKY) diets containing (a) 0.25% Ca/0.08% Mg, (b) 4.0% Ca/0.02% Mg, and (c) 4.0% Ca/0.08% mg, beginning at 6 weeks of age. SHR-SP and WKY rats receiving 4% Ca with the lower Mg content had lower blood pressures, hypomagnesemia, and hypomagnesuria, and grew poorly. SHR-SP receiving 4% Ca and the higher Mg diet had blood pressures no different from those of rats receiving the 0.25% Ca diet, in spite of having lower body weights. Rubidium flux studies in erythrocytes were not influenced by Ca or Mg in the diets. Plasma phosphate values were moderately reduced in rats receiving 4% Ca diets. Epinephrine and norepinephrine values were higher in SHR-SP than in WKY rats. Norepinephrine increased with stress in both strains, independent of diet. Epinephrine values were lower in SHR-SP receiving the 4% Ca diets and showed less of an increase with stress compared to SHR-SP receiving the 0.25% Ca diet. After 26 weeks of diets, SHR-SP and WKY rats were given 0.9% NaCl in their drinking water. NaCl increased blood pressure in SHR-SP irrespective of Ca content of the diet. These data suggest that a high Ca diet influences Mg homeostasis and adrenal medullary function in SHR-SP. Further, SHR-SP appear resistant to any blood pressure lowering effect of Ca irrespective of NaCl intake.
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PMID:Effect of high calcium diet on magnesium, catecholamines, and blood pressure of stroke-prone spontaneously hypertensive rats. 335 96

Seven healthy men, aged 21 to 30 years, were investigated by radionuclide cardiography at rest and during submaximal exercise at heavy (early) and during declining (late) alcohol intoxication. Control studies, in which alcohol was substituted by an isocaloric, isovolumic drink, were performed on a different day. The left ventricular ejection fraction at rest decreased from 59 to 56% during early intoxication (serum ethanol 35 +/- 6 mmol/l), whereas no change was observed in the ejection fraction during exercise. No significant change was recorded in stroke volume after alcohol consumption as opposed to a small increase after ingestion of the caloric drink. Plasma noradrenaline concentrations were elevated during exercise and early intoxication. During late intoxication (serum ethanol 21 +/- 5 mmol/l) the left ventricular ejection fraction at rest was increased by 7% compared with the baseline value. At rest the heart rate was increased from 68 +/- 7 to 84 +/- 15 beats/min, whereas cardiac output had reverted to the baseline value. Plasma noradrenaline at late intoxication was increased both at rest and during exercise compared with the baseline values. Apart from tachycardia and a reduction in left ventricular volumes during late intoxication no alcohol induced hemodynamic changes occurred during exercise.
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PMID:Cardiac function at rest and during exercise in early and late alcohol intoxication. 336 May 22

Haemodynamic data (thermodilution Swan-Ganz catheter and radial artery cannula) were collected in 17 patients (52.4 +/- 8 yr) during retrosigmoid approach for removal of an acoustic tumour in the seated position. Measurements were made before stimulation of posterior fossa structures (period 1) and during tumour dissection along the brain stem (period 2). Significant increases in systolic, diastolic and mean blood pressures, in pulmonary capillary wedge pressure, in cardiac index and in stroke index were observed during period 2, whereas heart rate, right atrial pressure and systemic vascular resistances were unaffected. The greater the size of the tumour and the difficulties in dissection, the greater were these intraoperative haemodynamic changes. In addition, the pulmonary arterial blood temperature and the noradrenaline plasma concentrations (double isotope enzymatic assay) increased significantly during period 2. In conclusion, the prolonged microsurgical technique of acoustic tumour dissection through the retrosigmoid approach may modify left ventricular loading conditions and may lead to pulmonary oedema, even if intravascular volume expansion was minimal and ventricular function was near normal.
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PMID:[Hemodynamic monitoring in microneurosurgical excision by sub- and retro-sinus approach in seated position in acoustic neurinoma]. 344 42

Increasing age impairs the regulation of blood pressure during posture change. The neuro-humoral and cardiovascular responses to head-up tilt were analysed in carefully-screened young and healthy elderly individuals. Mean blood pressure was significantly higher in the elderly but there were no differences in total peripheral resistance, heart rate, stroke volume and cardiac index. Age-related interactions were observed in the control of mean blood pressure, heart rate and stroke volume. Total peripheral resistance increased and cardiac index decreased but there was no difference in their control in the young and old. Noradrenaline, vasopressin, plasma renin activity and aldosterone all increased in response to the tilt. These observations indicate differences in the neuroendocrine responses and cardiovascular haemodynamics of young and old healthy individuals to head-up tilt and are particularly important because of all observations were made simultaneously in the same subject. It is suggested that a similar approach should be adopted in the investigation of patients with postural hypotension.
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PMID:Cardiovascular haemodynamics and the response of vasopressin, aldosterone, plasma renin activity and plasma catecholamines to head-up tilt in young and old healthy subjects. 351 87

Ten patients with advanced congestive heart failure were treated with an arginine vasopressin V1 antagonist during hemodynamic monitoring to determine the contribution of vasopressin to vasoconstriction in this disorder. The vasopressin antagonist caused a decrease in systemic vascular resistance in the three patients whose plasma vasopressin was greater than 4.0 pg/ml (average for the group was 2.4 +/- 0.6). Plasma vasopressin concentration correlated with the percent decrease of systemic vascular resistance (r = 0.70, p less than 0.025), serum sodium (r = 0.72, p less than 0.02) and serum creatinine (r = 0.85, p less than 0.005). To compare the relative roles of vasopressin, the renin-angiotensin system and the sympathetic nervous system, these patients also received captopril and phentolamine. Captopril decreased systemic vascular resistance by 20% (p less than 0.05), mostly in patients with high plasma renin activity. Levels of plasma renin activity ranged between 1 and 46 ng/ml per h (average 14.7 +/- 5.7) and correlated with serum sodium (r = 0.77, p less than 0.025), serum creatinine (r = 0.73, p less than 0.025) and right atrial pressure (r = 0.67, p less than 0.05). Phentolamine decreased systemic vascular resistance in all patients (average 34%, p less than 0.01), but the decrease did not correlate with the pretreatment norepinephrine concentration. Norepinephrine levels were elevated in all patients (694 +/- 110 pg/ml) and correlated with baseline stroke volume index (r = 0.75, p less than 0.025) and plasma renin activity (r = 0.67, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Contribution of vasopressin to vasoconstriction in patients with congestive heart failure: comparison with the renin-angiotensin system and the sympathetic nervous system. 351 28


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