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PubMedDate not supplied

Plethysmographic curve analysis and response to exercise in normal subjects, hypertension, and cardiac failure.

Occlusion plethysmographic recordings were obtained on 26 subjects prior to and immediately following repeated venous occlusions. A simple method of approximating the curve shape by 2 straight lines is described. The results indicate that, following an initial occlusion, the height of subsequent curves is reduced and the angulation between the 2 lines approximating the curves changes in a way that indicates that the principal mechanism is venous shunting. The degree of shunting was quantified by taking the relative percentage change in shape of the 2 lines approximating the curve, i.e., the percentage shunt. Venous shunting is shown to be much more marked after hand exercise than at rest in normal subjects and in those with heart failure or hypertension.

Adult↗
PubMed1982

Recurrence of hypertension in primary aldosteronism after discontinuation of spironolactone. Time course of changes in cardiac output and body fluid volumes.

Hemodynamic mechanisms underlying the hypertensive action of long-standing sodium overload were studied in ten subjects with aldosterone-producing adenoma. Arterial pressure was 129+/-4/91+/-4 mm Hg (mean+/-SEM) during spironolactone treatment, 177+/-5/114+/-3 mm Hg six weeks after the drug had been stopped, and 136+/-4/94+/-3 mm Hg two months after operation. In the six weeks following cessation of spironolactone, cardiac output, stroke volume, blood volume and sodium space were determined at weekly intervals. In each subject the biochemical syndrome of aldosterone-excess had been fully developed in two weeks. The hemodynamic changes in that period were also uniform. Mean arterial pressure in week 2 was increased by 20+/-3% with parallel increments of cardiac output and stroke volume of 22+/-5 and 30+/-6%. Blood volume and sodium space were increased by 11+/-2 and 29+/-4%. The patterns in weeks 2-6 were not uniform. In five subjects (age 33-49 yr) the hypertension was maintained through increased cardiac output; in week 6 it was 34+/-7% above its initial value, and stroke volume and blood volume were 37+/-4 and 16+/-4% above control. In the remaining five subjects (age 50-60 yr) cardiac output, stroke volume and blood volume returned to their initial values, and total peripheral resistance in week 6 was 36+/-13% above control. Sodium space remained expanded in both groups. The measurements after surgery confirmed the existence of the high-flow and high-resistance patterns; there was a decrease in cardiac output in the former group of subjects and a decrease in resistance in the latter. Apparently, increased resistance is not a direct consequence of increased flow. The observed age-related differences in hemodynamic patterns of sodium overload bear some resemblance to essential hypertension where a high-flow state of long duration may precede the ultimate phase of low vascular capacitance and high resistance.

Aldosterone↗
PubMed1996

Role of physical countermaneuvers in the management of orthostatic hypotension: efficacy and biofeedback augmentation.

OBJECTIVE: To evaluate the efficacy of various physical countermaneuvers in reducing orthostatic hypotension and its associated symptoms and to assess the efficacy of biofeedback training in enhancing the effectiveness of physical countermaneuvers. MATERIAL AND METHODS: In nine study subjects with neurogenic orthostatic hypotension, four training sessions on physical countermaneuvers were performed after tilt-up, three with visual feedback on the effect of physical countermaneuvers on blood pressure and other cardiovascular variables. Blood pressure change and orthostatic symptoms during tilt-up were determined, as were the changes in total peripheral resistance, stroke index, and heart rate. RESULTS: The five female and four male patients had a mean age of 53 years and a mean duration of symptoms of 4.2 years. On an orthostatic symptom scale of 0 to 10, these patients had a mean symptom score of 7.3. The increment in systolic blood pressure was better for some maneuvers (such as leg crossing and a combination) than others (such as neck flexion and abdominal contraction). Three patterns of responses to biofeedback were found. Simple maneuvers such as squatting did not improve with training; visual feedback was needed for maneuvers such as thigh contraction, and performance declined without biofeedback; the third pattern, seen in maneuvers such as leg crossing, showed continued improvement with training, even without biofeedback. A survey at 3 to 4 months after training revealed continued use of physical maneuvers (3.8 +/- 3.1 per day), increased standing time with each episode of presyncopal symptoms (8.3 +/- 5.8 minutes), and continued global symptomatic improvement. Total peripheral resistance, but not heart rate or stroke index, showed significant regression with blood pressure improvement. CONCLUSION: Physical countermaneuvers are efficacious in reducing orthostatic hypotension, can be augmented by use of biofeedback, and may significantly improve the functional outcome. The major mechanism of improvement is an increase in total peripheral resistance, presumably by reducing the vascular capacitance.

Adult↗
PubMed1999

Stenosis of the main artery supplying an organ: effect of end-organ vascular compliance on the poststenotic peak systolic velocity.

Prior studies have shown variable results using poststenotic peak systolic velocity to detect hemodynamically significant renal artery stenoses. We postulated that vascular compliance, which affects the arterial waveform and varies by a factor of at least 5 in vivo, affects the peak systolic velocity, perhaps explaining the aforementioned variable results using peak systolic velocity to detect stenoses. A hydraulic model was used to investigate the relationship between end-organ vascular compliance and the peak systolic velocity. The peak systolic velocity was found to be mildly dependent on vascular compliance, decreasing with decreasing compliance. These results help explain some of the reported variability using peak systolic velocity to detect hemodynamically significant renal artery stenoses, but the effect is not great enough to explain the variability completely. Other factors not investigated in this study must exist that also affect peak systolic velocity.

Blood Flow Velocity↗
PubMed2000

[Cardiovascular impact of end-stage renal insufficiency in children undergoing hemodialysis].

Cardiac hypertrophy and arterial dysfunction have been described in end-stage renal disease (ESDR) in adults. The incremental elastic modulus (Einc), is a marker of vascular wall material stiffness and an independant predictor of cardiovascular mortality in adults with ESRD on hemodialysis. The relationship between arterial changes and the heart is unknown in the children with ESRD in the same conditions. Using a high-resolution vascular ultrasound and a computerized system of measurement (Iotec), we assessed noninvasively 10 ESRD patients (mean +/- SD, age, 11.5 +/- 4 years; blood pressure [BP], 120 +/- 10/63 +/- 4 mmHg) and 10 age-, sex-, and BP-matched controls (mean +/- SD, age, 11 +/- 4 years; BP, 114 +/- 8/58 +/- 8 mmHg). The systolic and diastolic diameter of the common carotid artery (CCA), the thickness of the wall (intima-media thickness, IMT), the cross sectional compliance (CSC), the cross sectional distensibility (CSD) and the (Einc) were determined. CSC and CSD were evaluated at the same level of pressure. The CCA pressure waveform was obtained by applanation tonometry to assess the reflected wave by the augmentation index (AI). Further the left ventricular mass index was assessed. The flow mediated dilation (FMD) (endothelium-dependent function) and the vasodilation induced by glyceryl-trinitrate (GTNMD) (GTN, an endothelium-independent dilator) were evaluated at the brachial artery site. Compared to control subjects, ESRD patients have mechanical artery dysfunction with lower CSC and CSD (0.11 +/- 0.04 vs 0.18 +/- 0.05 mm2.mmHg-1; p < 0.01; 0.43 +/- 0.10 vs 0.82 +/- 0.20 mmHg-1.10(-2); p < 0.001) and higher Einc (2.60 +/- 1.00 vs 1.40 +/- 0.30 mmHg.10(3); p < 0.001). Furthermore an earlier return of the reflected pulse wave (AI -0.24 +/- 0.08 vs -0.58 +/- 0.06; p < 0.005) is correlated to LV mass index (r = 0.55, P < 0.01) that is significantly increased (134 +/- 63 vs 69 +/- 25 g/m2; p < 0.005). These patients have an impaired FMD (4 +/- 2 vs 7 +/- 1%; p = 0.02) with a normal GTNMD. This study shows that early arterial dysfunction can occur in children with ESRD.

Adult↗
PubMed2001

[Effect of taurine on the microvessel exchange function and adrenergic response of veins and arteries in the cat skeletal muscle].

In cats anesthetized with Uretan and perfused with a constant blood volume, Taurine induced responses of neither arterial nor venous vessels of the skeletal muscle but increased the capillary filtration coefficient without any significant change of the capillary pressure in the skeletal muscle's microvessels. Taurine also increased both the constrictor and the dilatory responses of the arterial and venous vessels. The mechanism of the Taurine effects upon the smooth muscle elements of arteries and veins as well as upon proper mechanisms of capillary pressure control and capillary filtration coefficient, seems to be calcium-dependent.

Adrenergic alpha-Agonists↗
PubMed2001

[Capacity and exchange functions of the kidney blood vessels at various leveles of venous outflow].

In perfusion of the cat hemodynamically isolated kidney with a constant blood flow volume, responses of venous vessels to noradrenaline did not depend on the venous outflow pressure level and only involved a diminishing of the blood filling which distinguishes kidneys from other organs. The renal veins' capacity decreased in response to noradrenaline practically completely disappears in high values of the venous outflow pressure. The renal capillary filtration coefficient was shown to equal 0.21 +/- 0.11, whereas the effect of changes in renal vein's pressure on implementation of the microvessels' exchange function in determined by the shifts of capillary hydrostatic pressure.

Animals↗
PubMedDate not supplied

Arterial stiffness.

Explore the source record for details and available documents.

Aging↗
PubMed2006

[Distribution of systemic vascular resistance disorders and its related factors in Hebei province].

OBJECTIVE: To analyze the distribution features of systemic vascular resistance (SVR) disorder in healthy subjects in Hebei province. METHODS: SVR and systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), pulse pressure (PP), heart rate (HR), cardiac output (CO), cardiac index (CI), stroke volume (SV), stroke index (SI), left ventricular ejection time (LVET), left cardiac work (LCW) and cardiovascular function were determined with Bioz. com Cardio Dynamics. Total cholesterol (TC), triglyceride (TG) and influencing factor were tested by automated hematology analyzer in 999 healthy subjects living in Hebei province. RESULTS: SVR disorder gradually increased with the ageing in healthy subjects and the prevalences of SVR disorders was higher among females than among males (P < 0.001). SVR was positively correlated with SBP, DBP, MAP, PP, LVET, body mass index (BMI), TC, and TG, and was inversely associated with HR, CO, CI, SV, SI, LCW, and arterial compliance (AC). CO and MAP were independent influencing factors with SVR. CONCLUSION: SVR disorder is associated with age, sex, and blood pressure in populations in Hebei province and may be a marker of vascular injury.

Adolescent↗
PubMed2005

[Vascular stiffness in chronic renal failure patients treated by hemodialysis].

Cardiovascular disease is a major cause of morbidity in patients with end-stage renal failure. Arterial stiffness measured by pulse wave velocity (PWV) is an independent risk factor for morbidity in end stage renal failure patients. The aim of our study was to evaluate the arterial stiffness in patients with chronic renal failure. In 20 chronic renal failure patients treated by hemodialysis (HD) we assessed the PWV of the carotic artery as well as artery diameter and distensibility, systolic pressure (SBP), diastolic pressure (DBP), pulse pressure (PP), and basal biochemical parameters and compared them with the values determined in 20 healthy controls of comparable age. PWV and PP are significantly (p < 0.001, p < 0.05) higher and distensibility of the carotic artery was significantly lower (p < 0.001) compared to a control group SBP and DBP were < 140/90 mmHg in HD patients (high normotensive range) but were significantly (p < 0.05) higher than in a control group. In HD patients PP was correlated with arterial distensibility r = -0.600 (p < 0.005), and systolic artery rice r = -0.408 (p < 0.05). SBP was correlated with PP r = 0.689 (p < 0.0007) and with arterial distensibility r = -0.476 (p < 0.03), arterial diameter to systolic artery rice r = -0.463 (p < 0.03), systolic artery rice to arterial distensibility r = 0.885 (p < 0.00001), intima media to arterial distensibility r = 0.815 (p < 0.00001), intima media to arterial compliance r = 0.893 (p < 0.00001). Our results suggest that not only established hypertension but also high normotensive pressure could cause arterial stiffness absened in chronic renal failure patients.

Adult↗
PubMed2006

Comparison of arterial compliance indices derived via beat-to-beat blood pressure waveforms: aging and ethnicity.

Reduced arterial compliance has been implicated as a risk factor for future cardiovascular events in hypertensive patients. Recently, several non-invasive techniques have been used to access arterial compliance. However, comparisons of these techniques with older individuals and African-Americans have not been done. In the present study, beat-to-beat blood pressure was examined in 75 males and females (n = 24 old Caucasian; n = 24 young Caucasian; n = 27 African-Americans) who were part of the Baltimore Longitudinal Study of Aging (BLSA). Resting beat-to-beat blood pressure (5 minutes) was assessed using the PORTAPRES Ambulatory Blood Pressure Device. Results indicated that the three-element windkessel and the stroke volume-pulse pressure ratio measures of arterial compliance provide comparable estimates. Specifically, arterial compliance is reduced in the oldest individuals in our sample with young and African-Americans showing higher compliance. These results indicate that the simpler stroke volume-pulse pressure ratio provides reliable estimates of arterial compliance in both older adults and African-Americans. This technique is an excellent means to assess arterial compliance and is a useful measure to determine risk for adverse cardiovascular events.

Aged↗
PubMed1985

Cardiovascular adrenoreceptor balance during hemorrhagic hypotension and shock.

The primary aim of this study was to examine the hypothesis that the ability of the cardiovascular system to compensate for hemorrhagic hypotension is controlled by a balance between the relative influence of the alpha 1 and extrasynaptic alpha 2 adrenoreceptors. Previous studies have implied that, although both receptors participate in the baroreceptor response to hypotension, only the extrasynaptic alpha 2 receptors are able to maintain the compensatory vasoconstrictor effort for a prolonged period of time. In each experiment two Sprague-Dawley rats were anesthetized and subjected to a modified Wiggers hemorrhagic shock protocol. One rat in each pair was pretreated with either 25 mg/kg of the cyclooxygenase inhibitor sodium meclofenamate or 0.5 mg/kg of the selective alpha 1 antagonist prazosin. The results indicate that neither drug interfered with the normal maximum compensatory effort as defined by the maximum blood loss (ie, reduced total vascular capacitance) when mean arterial pressure (MAP) was reduced to 30 mmHg by hemorrhage. In fact, when normalized for pre-hemorrhage MAP, it was apparent that prazosin, which lowered pre-hemorrhage MAP, may have actually improved the compensatory response. Sodium meclofenamate increased the time to reach the maximum compensatory effort (comp time), while prazosin increased the time to reach 20% uptake from the blood reservoirs (decomp time). Since both drugs enhanced the total time (comp + decomp) and both are known to interfere with alpha 1 function, these studies support the hypothesis stated above.

Animals↗
PubMed1993

Modification of carotid chemoreceptor-induced changes in renal haemodynamics and function by carotid baroreflex in dogs.

1. Mongrel dogs were anaesthetized with thiopental sodium and chloralose and artificially ventilated. The carotid sinus regions were vascularly isolated and perfused either with arterial or mixed (arterial and venous) blood (PO2, 44.2 +/- 3.3 mmHg, mean +/- S.E.M.) to stimulate the chemoreceptors. Cervical vagosympathetic trunks were ligated and atenolol (2 mg kg-1, I.V.) was given in all dogs and gallamine triethiodide (3 mg kg-1 h-1, I.V.) was given in two dogs. Renal blood flow was measured by an electromagnetic flowmeter, glomerular filtration rate by creatinine clearance, sodium excretion by flame photometry and solute excretion by osmometry. The viability of the preparations was tested by recording total vascular capacitance responses to stimulation of carotid baro- and chemoreceptors. 2. In eleven tests in seven dogs at a constant aortic pressure of 88.9 +/- 2.6 mmHg stimulation of carotid chemoreceptors at a high carotid sinus pressure (194.0 +/- 3.6 mmHg) resulted in significant increases in urine flow of 22.8 +/- 3.0%, urinary sodium excretion of 30.7 +/- 5.2%, fractional sodium excretion of 35.3 +/- 18.6%, osmolar excretion of 17.5 +/- 4.1% and a decrease in free water clearance of 30.8 +/- 3.1% without significant changes in urinary sodium concentration, renal blood flow, glomerular filtration rate, and filtration fraction. 3. In seventeen tests in these seven dogs at a constant aortic pressure of 94.0 +/- 2.2 mmHg, stimulation of carotid chemoreceptor at a low carotid sinus pressure (72.0 +/- 1.3 mmHg) resulted in significant decreases in renal blood flow of 10.6 +/- 2.5%, glomerular filtration rate of 19.6 +/- 6.8%, filtration fraction of 13.2 +/- 5.5%, urine flow of 23.4 +/- 4.1%, urinary sodium concentration of 20.3 +/- 4.1%, urinary sodium excretion of 38.5 +/- 4.6%, fractional sodium excretion of 20.2 +/- 7.7%, osmolar excretion of 23.9 +/- 4.0% and an increase in free water clearance of 23.1 +/- 2.5%. 4. The results show that moderate stimulation of carotid chemoreceptors at a low carotid sinus pressure, when the activity in renal nerves is high and blood volume is low, can produce significant reflex decreases in renal haemodynamic and functional variables. However, at a high carotid sinus pressure when the renal sympathetic activity is low and blood volume is high, carotid chemoreceptor stimulation produces diuresis and natriuresis but no change in renal haemodynamics.

Animals↗
PubMed1998

Lung diffusing capacity and exercise in subjects with previous high altitude pulmonary oedema.

Subjects with a history of high-altitude pulmonary oedema (HAPE) have increased pulmonary artery pressure and more ventilation-perfusion (V'A/Q') inhomogeneity with hypoxia and exercise. We used noninvasive methods to determine whether there are differences in the pulmonary diffusing capacity for carbon monoxide (DL,CO) and cardiac output (Q') during exercise, indicative of a more restricted pulmonary vascular bed in subjects with a history of HAPE. Eight subjects with radiographically documented HAPE and five controls with good altitude tolerance had standard pulmonary function testing and were studied during exercise at 30 and 50% of normoxic maximal oxygen consumption (V'O2) at an inspiratory oxygen fraction of 0.14 and 0.21. DL,CO and Q' were measured by CO and acetylene rebreathing techniques. HAPE-resistant subjects had 35% greater functional residual capacity than HAPE-susceptible subjects. Vital capacity and total lung capacity were also 7-10% greater. There were no differences in airflow rates or resting diffusing capacity. However, DL,CO in HAPE-susceptible subjects was lower in hypoxia and with exercise, and showed less increase (32 versus 49%) with the combined stimulus of hypoxic exercise. HAPE-susceptible subjects had smaller increases in stroke volume, Q', and ventilation during exercise. The findings are consistent with lower pulmonary vasoconstriction, greater vascular capacitance and greater ventilatory responsiveness during exercise in subjects who are resistant to high-altitude pulmonary oedema. Their larger lung volumes suggest a constitutional difference in pulmonary parenchyma or vasculature, which may be a determinant of high-altitude pulmonary oedema resistance.

Adult↗
PubMed1998

[Contractile adrenergic responses of the arterial and venous vessels and transcapillary fluid exchange in the cat small intestine during taurine administration].

Taurine induced no responses of the intestine arterial and venous vessels in cats. Following the taurine administration, a decrease of the capillary filtration coefficient occurs against the background of the capillary pressure in the intestine microvessels, and adrenergic constrictor responses of the vessels are enhanced. The latter responses reduced with verapamil infusion become again enhanced following taurine administration.

Adrenergic alpha-Agonists↗
PubMed2006

Pharmacological and electrophysiological characterization of store-operated currents and capacitative Ca(2+) entry in vascular smooth muscle cells.

Capacitative Ca(2+) entry (CCE) in vascular smooth muscle cells contributes to vasoconstrictor and mitogenic effects of vasoactive hormones. In A7r5 rat aortic smooth muscle cells, measurements of cytosolic free Ca(2+) concentration ([Ca(2+)](i)) have demonstrated that depletion of intracellular Ca(2+) stores activates CCE. However, there is disagreement in published studies regarding the regulation of this mechanism by the vasoconstrictor hormone [Arg(8)]-vasopressin (AVP). We have employed electrophysiological methods to characterize the membrane currents activated by store depletion [store-operated current (I(SOC))]. Because of different recording conditions, it has not been previously determined whether I(SOC) corresponds to CCE measured using fura-2; nor has the channel protein responsible for CCE been identified. In the present study, the pharmacological characteristics of I(SOC), including its sensitivity to blockade by 2-aminoethoxydiphenylborane, diethylstilbestrol, or micromolar Gd(3+), were found to parallel the effects of these drugs on thapsigargin- or AVP-activated CCE measured under identical external ionic conditions using fura-2. Thapsigargin-stimulated I(SOC) was also measured in freshly isolated rat mesenteric artery smooth muscle cells (MASMC). Members of the transient receptor potential (TRP) family of nonselective cation channels, TRPC1, TRPC4, and TRPC6, were detected by reverse transcription-polymerase chain reaction and Western blot in both A7r5 cells and MASMC. TRPC1 expression was reduced in a stable A7r5 cell line expressing a small interfering RNA (siRNA) or by infection of A7r5 cells with an adenovirus expressing a TRPC1 antisense nucleotide sequence. Thapsigargin-stimulated I(SOC) was reduced in both the TRPC1 siRNA- and TRPC1 antisense-expressing cells, suggesting that the TRPC1 channel contributes to the I(SOC)/CCE pathway.

Animals↗
PubMed1990

Assessment of the splanchnic vascular capacity and capacitance using quantitative equilibrium blood-pool scintigraphy.

A series of human and animal experiments were carried out to assess the usefulness of equilibrium blood pool scintigraphy (EBPS) to study acute changes of the splanchnic vascular capacity and the splanchnic vascular pressure-volume (P-V) relationship. Corrected regional abdominal count rate changes, before and after various pharmacologic interventions, were used to assess regional splanchnic vascular volume changes. Animals were instrumented to manipulate and record splanchnic venous pressures. In patients, splanchnic vascular capacity increased by 5.2 +/- 6.9% (p less than 0.001) after 0.6 mg sublingual nitroglycerin while no significant change was noted after sugar pills (0.9 +/- 5.2%, p greater than 0.3). In dogs, splanchnic vascular capacity decreased by a mean of 16% during infusion of angiotensin (p less than 0.001) and increased by a mean of 32% during infusion of nitroprusside (p less than 0.001). The splanchnic vascular P-V curve was shifted rightwards during nitroglycerin administration. Thus, using the radionuclide technique we detected the expected qualitative and quantitative shifts in splanchnic capacity and capacitance. We conclude that EBPS is a useful method to assess acute changes of 1) the splanchnic vascular P-V relationship, in invasive animal studies, and 2) the splanchnic vascular capacity in noninvasive human and animal studies.

Adult↗