Greater Increase In Cardiac Output Research Articles

#6201 CHANGES ON LEFT VENTRICULAR FUNCTION AND CHARACTERISTICS ACCORDING TO THE DEGREE OF INTERDIALYTIC WEIGHT GAIN IN MAINTENANCE HEMODIALYSIS PATIENTS

Abstract Background and Aims Pronounced pulmonary circulation overloading has been observed in hemodialysis patients with higher fluid intake over the long interdialytic interval. This study aimed to evaluate the impact of the degree of fluid accumulation on left ventricular (LV) systolic and diastolic function and sizing characteristics. Method For the present analysis, 41 patients receiving maintenance hemodialysis thrice-weekly were divided by the recommended threshold of interdialytic-weight-gain corrected for dry weight (IDWG%) into a higher (>4.5%) and a lower (<4.5%)IDWG% group. All participants underwent 4 echocardiographic assessments at the start and the end of the 3-day and the 2-day interdialytic interval in a cross over design. Results Over the 3-day interval, significant increments in stroke volume (SV) were observed for both groups, but were more prominent in the higher IDWG% group(>4.5% 18.63±22.84vs. <4.5% 12.6±14.48mmHg, p = 0.04). Similarly, a greater increase in cardiac output was evidenced in patients with higher IDWG% over the 2-day interval (>4.5% 1.31±1.38 vs.<4.5% 0.36±2.08L/m2, p = 0.012). With regards to diastolic function, a significant increase in E/A and E/E’m ratios was observed over the 3-day interval, but significant between-group differences in interdialytic changes were detected only for the E/A ratio (IDWG>4.5% 0.35±0.29 vs. <4.5% 0.06±0.44, p = 0.035). Left atrial dimensions and LV mass were enlarged to a similar extent in both study-groups during both intervals. Conclusion Patients exceeding the recommended threshold of interdialytic fluid accumulation experience higher increases in SV and deterioration of preload-dependent indexes of diastolic function, particularly during the 3-day interval.

CHANGES ON LEFT VENTRICULAR FUNCTION AND CHARACTERISTICS ACCORDING TO THE DEGREE OF INTERDIALYTIC WEIGHT GAIN IN MAINTENANCE HEMODIALYSIS PATIENTS

Objective: Pronounced pulmonary circulation overloading has been observed in hemodialysis patients with higher fluid intake over the long interdialytic interval. This study aimed to evaluate the impact of the degree of fluid accumulation on left ventricular (LV) systolic and diastolic function and sizing characteristics. Design and method: For the present analysis, 41 patients receiving maintenance hemodialysis thrice-weekly were divided by the recommended threshold of interdialytic-weight- gain corrected for dry weight (IDWG%) into a higher (>4.5%) and a lower ( < 4.5%) IDWG% group. All participants underwent 4 echocardiographic assessments at the start and the end of the 3-day and the 2-day interdialytic interval in a crossover design. Results: Over the 3-day interval, significant increments in stroke volume (SV) were observed for both groups, but were more prominent in the higher IDWG% group (>4.5% 18.63 ± 22.84vs. <4.5%12.6 ± 14.48mmHg, p = 0.04). Similarly, a greater increase in cardiac output was evidenced in patients with higher IDWG% over the 2- day interval (>4.5%1.31 ± 1.38 vs.<4.5%0.36 ± 2.08L/m 2, p = 0.012). With regards to diastolic function, a significant increase in E/A and E/E’m ratios was observed over the 3-day interval, but significant between-group differences in interdialytic changes were detected only for the E/A ratio (IDWG>4.5% 0.35 ± 0.29 vs. <4.5% 0.06 ± 0.44, p = 0.035). Left atrial dimensions and LV mass were enlarged to a similar extent in both study-groups during both intervals. Conclusions: Patients exceeding the recommended threshold of interdialytic fluid accumulation experience higher increases in SV and deterioration of preload- dependent indexes of diastolic function, particularly during the 3-day interval.

Cardiovascular adjustments to cold pressor test in postmenopausal women and the impact of α1-adrenergic blockade.

We investigate the impact of menopause on cardiovascular adjustments to the cold pressor test (CPT) and the role of the α1-adrenergic receptor. Ten young women (YW) and nine postmenopausal women (MW) underwent 1min of CPT in control and α1-blockade conditions (0.03mg‧kg-1 of oral prazosin). CPT increased heart rate (HR) (YW: ∆20 ± 3bpm; MW: ∆13 ± 2bpm) and stroke volume (SV; YW: ∆15 ± 8ml; MW: ∆9 ± 6ml; p = 0.01 for time) and evoked a greater increase in cardiac output (CO) in YW (YW: ∆2.1 ± 0.2l‧m-1; MW: ∆1.3 ± 0.5l‧m-1; p = 0.01). α1-Blockade increased baseline HR and did not change HR, SV, and CO responses to CPT. MW presented an exaggerated systolic blood pressure (BP) response (YW: ∆38 ± 9mmHg; MW: ∆56 ± 24mmHg; p = 0.03). The α1-blockade did not change baseline BP while blunting its response. Total vascular resistance (TVR) was similar between groups at baseline and increased during CPT only in MW (YW: ∆2.3 ± 1.4mmHg‧L-1‧min; MW:∆6.8 ± 5.9mmHg‧L-1‧min). Under α1-blockade, the TVR increase during CPT was attenuated in MW and abolished in YW (YW: ∆0.3 ± 1.2mmHg‧L-1‧min and MW: ∆3.0 ± 2.0mmHg‧L-1‧min). CPT did not change femoral vascular conductance (FVC) in either group before the blockade (YW: ∆-0.3 ± 4.0ml‧min-1‧mmHg-1; MW: ∆-0.2 ± 0.8ml‧min-1‧mmHg-1); however, FVC tended to increase in young women (YW: ∆1.3 ± 1.0ml‧min-1‧mmHg-1; MW: ∆0.1 ± 1.5ml‧min-1‧mmHg-1; p = 0.06) after the α1-blockade. In postmenopausal women, the cardiac ability to adjust to CPT is blunted and α1-adrenergic receptor stimulation is important for the increase in stroke volume. In addition, the peripheral effect of α1-adrenergic receptor stimulation seems to be increased in postmenopausal women.

Norepinephrine versus phenylephrine infusion for preventing postspinal hypotension during cesarean section for twin pregnancy: a double-blinded randomized controlled clinical trial

BackgroundCompared with singleton pregnancy, twin gestation is featured by a greater increase in cardiac output. Therefore, norepinephrine might be more suitable than phenylephrine for maintaining blood pressure during cesarean section for twins, as phenylephrine causes reflex bradycardia and a resultant decrease in cardiac output. This study was to determine whether norepinephrine was superior to phenylephrine in maintaining maternal hemodynamics during cesarean section for twins.MethodsInformed consent was obtained from all the patients before enrollment. In this double-blinded, randomized clinical trial, 100 parturients with twin gestation undergoing cesarean section with spinal anesthesia were randomized to receive prophylactic norepinephrine (3.2 μg/min) or phenylephrine infusion (40 μg/min). The primary outcome was the change of heart rate and blood pressure during the study period. The secondary outcomes were to compare maternal complications, neonatal outcomes, Apgar scores and umbilical blood acid-base status between the two vasopressors.ResultsThere was no significant difference observed for the change of heart rate between two vasopressors. The mean standardized area under the curve of heart rate was 78 ± 12 with norepinephrine vs. 74 ± 11 beats/min with phenylephrine (mean difference 4.4, 95%CI − 0.1 to 9.0; P = .0567). The mean standardized area under the curve of systolic blood pressure (SBP) was significantly lower in parturients with norepinephrine, as the mean of differences in standardized AUC of SBP was 6 mmHg, with a 95% CI from 2 to 9 mmHg (P = .0013). However, requirements of physician interventions for correcting maternal hemodynamical abnormalities (temporary cessation of vasopressor infusion for reactive hypertension, rescuing vasopressor bolus for hypotension and atropine for heart rate less < 50 beats/min) and neonatal outcomes were also not significantly different between two vasopressors.ConclusionInfusion of norepinephrine was not associated with less overall decrease in heart rate during cesarean section for twins, compared with phenylephrine.Trial registrationChinese Clinical Trial Registry (ChiCTR1900021281).

Implications of Doppler Echocardiography-guided Heart Rate Modulation Using Ivabradine.

Objective Heart rate modulation therapy using ivabradine reduces both morbidity and mortality in patients with systolic heart failure. However, the target heart rate for this patient population remains to be elucidated. Methods In this prospective observational study, we included patients with heart failure and a reduced ejection fraction who received 5.0 mg/day of ivabradine for three days. At baseline and three days later, the overlap length between E-wave and A-wave using trans-mitral Doppler echocardiography, as well as the cardiac output using AESCLONE mini, were simultaneously measured. The associations between Δ overlap length and Δ cardiac output were then investigated. Results Eight patients [77 (53, 87) years old, 2 men] were included. The heart rate decreased from 81 (69, 104) bpm down to 64 (57, 79) bpm (p=0.012). The overlap length increased in four patients and decreased in the other four patients. During the time period of ivabradine therapy, patients who had a greater decrease in overlap length had a greater increase in cardiac output (r=0.84, p=0.009). Conclusion Decreases in the overlap length between E-wave and A-wave by Doppler echocardiography were associated with an increase in the cardiac output while on ivabradine therapy. The implications of Doppler echocardiography-guided heart rate modulation therapy targeting a minimal overlap length therefore require further evaluation in larger, prospective studies.

Augmented Hemodynamic Responses in Obese Young Men during Dynamic Exercise: Role of the Muscle Metaboreflex.

Studies found that cardiovascular responses to exercise are enhanced in individuals with obesity and are associated with a greater cardiac output (CO) response compared to normal weight controls. However, the mechanisms underlying these altered responses during dynamic exercise are not clear. We investigated whether the cardiovascular responses mediated by the muscle metaboreflex (MMR) activation are augmented in obese men during both static and dynamic exercise. Twenty males (10 obese (OG) and 10 non-obese (NOG)) were studied. Changes in CO, mean arterial pressure (MAP), and total vascular conductance (TVC) were compared between the two groups during dynamic handgrip exercise (DHE), post-exercise muscular ischemia (PEMI), and dynamic exercise corresponding to 40%, 60% and 80% workloads. Subjects completed 2 min of DHE at 30% of MVC, followed by 2 min of PEMI. MAP, CO, and TVC responses to DHE and dynamic exercise were significantly higher in OG, whereas there were no differences during PEMI. Increases in CO and MAP during mild to heavy dynamic exercise were seen in both groups, but the changes in these variables were greater in the OG. There were no significant differences in TVC between the two groups. Compared to NOG, the augmented blood pressure response to DHE and dynamic exercise in OG was associated with a greater increase in CO. Thus, the augmented CO and MAP responses were not associated with the activation of the MMR. Consequently, additional factors specific to obesity, such as the mechanoreflex, may have been involved.

Efficacy and safety of 20% albumin fluid loading in healthy subjects: a comparison of four resuscitation fluids.

Recently, buffered salt solutions and 20% albumin (small volume resuscitation) have been advocated as an alternative fluid for intravenous resuscitation. The relative comparative efficacy and potential adverse effects of these solutions have not been evaluated. In a randomized, double blind, cross-over study of six healthy male subjects we compared the pulmonary and hemodynamic effects of intravenous administration of 30 ml/kg of 0.9% saline, Hartmann's solution and 4% albumin, and 6 ml/kg of 20% albumin (albumin dose equivalent). Lung tests (spirometry, ultrasound, impulse oscillometry, diffusion capacity, and plethysmography), two- to three-dimensional Doppler echocardiography, carotid applanation tonometry, blood gases, serum/urine markers of endothelial, and kidney injury were measured before and after each fluid bolus. Data were analyzed with repeated measures ANOVA with effect of fluid type examined as an interaction. Crystalloids caused lung edema [increase in ultrasound B line (P = 0.006) and airway resistance (P = 0.009)], but evidence of lung injury [increased angiopoietin-2 (P = 0.019)] and glycocalyx injury [increased syndecan (P = 0.026)] was only observed with 0.9% saline. The colloids caused greater left atrial stretch, decrease in lung volumes, and increase in diffusion capacity than the crystalloids, but without pulmonary edema. Stroke work increased proportionally to increase in preload with all four fluids (R2 = 0.71). There was a greater increase in cardiac output and stroke volume after colloid administration, associated with a reduction in afterload. Hartmann's solution did not significantly alter ventricular performance. Markers of kidney injury were not affected by any of the fluids administrated. Bolus administration of 20% albumin is both effective and safe in healthy subjects. NEW & NOTEWORTHY Bolus administration of 20% albumin is both effective and safe in healthy subjects when compared with other commonly available crystalloids and colloidal solution.

The Effects of Hemodynamic Unloading in African Americans Implanted with Left Ventricular Assist Devices.

We aim to evaluate the echocardiographic/hemodynamic effects of left ventricular assist devices in African American (AA) versus non-AA patients undergoing ramp speed optimization and its subsequent effect on readmissions. In 65 patients (26 AA), no differences in baseline echocardiographic/hemodynamic parameters were noted. During ramp testing, there was a significantly greater increase in cardiac output (slope: 0.29 ± 0.24 vs. 0.15 ± 0.12, p < 0.01) with more rapid decrease in left ventricular end-diastolic diameter (slope: -0.21 ± 0.14 vs. -0.13 ± 0.07 L/min, p < 0.01) in the AA group. AAs had higher all-cause, but similar heart failure readmission rate as compared with the non-AA group.

Dynamic left intraventricular obstruction in patients with septic shock: pathogenetic role and prognostic implications

Background Left intraventricular flow obstruction (IVO) has been classically described in asymmetric hypertrophic cardiomyopathy, usually at the level of the left ventricular outflow tract (LVOT) or at midcavitary level, which is due to systolic anterior movement of the anterior leaflet of the mitral valve. This phenomenon has also been previously described in certain clinical situations mainly revolving around hypovolemia and catecholamine exposure and recently as a frequent event in patients with septic shock with an important correlation with fluid responsiveness. Multiple studies have demonstrated that static parameters limited the predictive value for fluid responsiveness, whereas dynamic parameters have shown a greater clinical use, including respiratory changes in aortic blood velocity, superior vena cava collapsibility, inferior vena cava (IVC) collapsibility, and changes in stroke volume and Cardiac Output (CO) owing to passive leg raising. Objective This study aimed to assess (a) the prevalence of dynamic IVO in patients with septic shock; (b) relation among IVO, volume status, and fluid responsiveness; and (c) relation between IVO and in-hospital mortality. Patients and methods A total of 40 patients with septic shock were studied over a period of 1 year for the presence of Doppler signs of dynamic IVO, clinical characteristics, hemodynamic parameters, and APACHE II and SOFA scoring. Echocardiographic data including IVC collapsibility, CO, LVOT mean and peak pressure gradient, LVOT maximum velocity, and midcavitary Doppler pattern were recorded initially and following fluid resuscitation (30 ml/kg). Patients were categorized into two groups: group A included patients with IVO and group B included patients without IVO. There was a statistically nonsignificant difference between both groups regarding the baseline demographic, clinical, and hemodynamic parameters. Results A total of 40 (45% were males and 55% females) patients, with a mean age of 52±20 years, were studied, of whom a total of 13 (32%) had IVO versus 27 patients without IVO. Following fluid infusion, as compared with group B, group A showed significantly greater increase in Cardiac Output (COP) (5.85±1.4 vs. 4.4±1.8, P=0.0203) and IVC collapsibility (54.42±6.8 vs 50.56±13, P=0.42). ICU mortality was significantly higher in patients with IVO [10/13 (76.9%)] versus patients without IVO [7/27 (25.9%), P Conclusion Dynamic left IVO is not uncommon in patients with septic shock in ICU. Response to fluid infusion was significantly higher in patients with IVO compared with patients without IVO, pointing to an additional role of fluid resuscitation in patients with sepsis.

Preliminary investigation of orally administered benazepril in horses with left‐sided valvular regurgitation

Despite the paucity of data available, orally administered angiotensin-converting enzyme (ACE) inhibitors are empirically used in horses with valvular regurgitation. Evaluate the echocardiographic and hormonal changes in response to oral benazepril in horses with left-sided valvular regurgitation. Prospective, randomised double-blind, placebo-controlled trial. Horses with mitral valve (MR) and/or aortic valve regurgitation (AR) received oral benazepril (n = 6) at a dosage of 1 mg/kg q 12 h or a placebo (n = 5) for 28 days. Echocardiography was performed before drug administration and after 28 days of treatment. Plasma renin activity, serum ACE activity, angiotensin II concentration, aldosterone concentration and biochemical variables were measured before drug administration and after 7 and 28 days of treatment. Relative to baseline, horses treated with benazepril had statistically significant reduction in left ventricular internal diameter in systole (mean difference between groups = -0.97 cm; 95% CI = -1.5 to -0.43 cm), aortic sinus diameter (-0.31 cm; -0.54 to -0.07 cm), and percentage of the aortic annulus diameter occupied by the base of the AR jet (-17.05%; -31.17 to -2.93%) compared with horses receiving a placebo. In addition, horses treated with benazepril had a significantly greater increase in cardiac output (11.95 L/min; 1.17-22.73 L/min) and fractional shortening (7.59%; 3.3-11.88%) compared with horses receiving a placebo. Despite profound serum ACE inhibition, renin activity and concentrations of angiotensin II and aldosterone were not significantly different between treatment groups or among time points. Very small sample size and short treatment period. Treatment with oral benazepril resulted in statistically significant echocardiographic changes that might indicate reduced cardiac afterload in horses with left-sided valvular regurgitation. Additional studies with a larger sample size will be necessary to determine if administration of benazepril is beneficial in horses with valvular regurgitation. The Summary is available in Spanish - see Supporting Information.

The haemodynamic effects of bolus versus slower infusion of intravenous crystalloid in healthy volunteers

PurposeThis pilot study aimed to characterise the haemodynamic effect of 1L of IV normal saline (NS) administered as a rapid versus slow infusion on cardiac output (CO), heart rate (HR), systemic blood pressures, and carotid blood flow in six healthy volunteers. Materials and methodsSix healthy male volunteers aged 18–65years were randomized to receive 1L NS given over 30min or 120min. On a subsequent study session the alternate fluid regimen was administered. Haemodynamic data was gathered using a non-invasive finger arterial pressure monitor (Nexfin®), echocardiography and carotid duplex sonography. Time to micturition and urine volume was also assessed. ResultsCompared to baseline, rapid infusion of 1L of saline over 30min produced a fall in Nexfin®-measured CO by 0.62L/min (p<0.001), whereas there was a marginal but significant increase during infusion of 1L NS over 120min of 0.02L/min (p<0.001). This effect was mirrored by changes in HR and blood pressure (BP) (p<0.001). There were no significant changes in carotid blood flow, time to micturition, or urine volume produced. ConclusionsSlower infusion of 1L NS in healthy male volunteers produced a greater increase in CO, HR and BP than rapid infusion.

Effect of Acute Stress on Cardiac Output and Systemic Peripheral Resistance in Obese Young Adults

Obesity is major problem in present population especially in children and young adults. Obesity is a state of excess adipose tissue mass. Stress is inevitable in the present scenario. Obesity adversely affects almost all the systems of the body including cardiovascular and respiratory system and reduces exercise tolerance & stress tolerance. Exposure to sudden extreme stress is commonly seen in medical students. Therefore the present study was conducted to assess the effect of acute stress on cardiac output and systemic peripheral resistance in obese young adults. Sixty asymptomatic healthy male medical students, aged 17–25 years, participated voluntarily in the present study. Subjects were divided in to two groups of 30 each. Group A comprised of non-obese (BMI 30). Cold pressor test (CPT) was used to induce acute stress which involves immersion of hand in cold water of 8°c for 2 minutes. Cardiac output and peripheral resistance were measured by using Impedance Cardiovasograph (Nivomon). All the parameters were recorded before and immediately after cold pressor test in both the groups. Results showed significant increase in cardiac output and systemic peripheral resistance (p 0.05) in control group but these were significantly higher in obese subjects of group B. Results show greater increase in cardiac output and systemic peripheral resistance in obese on exposure to acute stress and delayed recovery to baseline values in comparison to non obese.

Blood pressure changes following aerobic exercise in Caucasian and Chinese descendants.

Acute aerobic exercise produces post-exercise hypotension (PEH). Chinese populations have lower prevalence of cardiovascular disease compared to Caucasians. PEH may be associated cardiovascular disease through its influence on hypertension. The purpose of this study was to compare PEH between Caucasian and Chinese subjects following acute aerobic exercise. 62 (30 Caucasian and 32 Chinese, 50% male) subjects underwent measurement of peripheral and central hemodynamics as well as arterial and cardiac evaluations, 30 min and 60 min after 45 min of treadmill exercise. Caucasians exhibited significantly higher baseline BP than the Chinese. While the reduction in brachial artery systolic BP was greater in Caucasian than in the Chinese, there was no difference in changes in carotid systolic BP between the groups. The increase in cardiac output and heart rate was greater in the Chinese than Caucasians, but total peripheral resistance and leg pulse wave velocity decreased by a similar magnitude in the Chinese and Caucasian subjects. We conclude that acute aerobic exercise produces a greater magnitude of PEH in peripheral systolic BP in Caucasian compared to Chinese subjects. The different magnitude in PEH was caused by the greater increase in cardiac output mediated by heart rate, with no change in stroke volume. It is possible that initial BP differences between races influenced the findings.

Sex differences in blood pressure responses to mental stress are abolished after a single bout of exercise: underlying hemodynamic mechanisms

We aimed to investigate whether the pressor responses to mental stress (MS) are exaggerated in men due to heightened cardiac responses, before and after a bout of exercise. Fifteen men and 19 women underwent a protocol consisting of blood pressure (BP), cardiac output (CO) and forearm vascular assessments at baseline and during MS, and these measurements were performed before and 60 min after a bout of exercise. Before exercise, BP response was significantly augmented in men (Δ16 ± 2 mmHg) compared to women (Δ11 ± 1 mmHg). This BP response was accompanied by greater increases in CO in men and similar vascular responses between sexes. After exercise, BP and CO responses to MS were attenuated in men and, consequently, no sex differences were observed. Vascular responses were not affected by exercise. The mechanism underlying the lack of sex differences in BP response to MS after exercise was found to be a marked attenuation in CO in men only.

Impact of body position on central and peripheral hemodynamic contributions to movement-induced hyperemia: implications for rehabilitative medicine

This study used alterations in body position to identify differences in hemodynamic responses to passive exercise. Central and peripheral hemodynamics were noninvasively measured during 2 min of passive knee extension in 14 subjects, whereas perfusion pressure (PP) was directly measured in a subset of 6 subjects. Movement-induced increases in leg blood flow (LBF) and leg vascular conductance (LVC) were more than twofold greater in the upright compared with supine positions (LBF, supine: 462 ± 6, and upright: 1,084 ± 159 ml/min, P < 0.001; and LVC, supine: 5.3 ± 1.2, and upright: 11.8 ± 2.8 ml·min⁻¹ ·mmHg⁻¹, P < 0.002). The change in heart rate (HR) from baseline to peak was not different between positions (supine: 8 ± 1, and upright: 10 ± 1 beats/min, P = 0.22); however, the elevated HR was maintained for a longer duration when upright. Stroke volume contributed to the increase in cardiac output (CO) during the upright movement only. CO increased in both positions; however, the magnitude and duration of the CO response were greater in the upright position. Mean arterial pressure and PP were higher at baseline and throughout passive movement when upright. Thus exaggerated central hemodynamic responses characterized by an increase in stroke volume and a sustained HR response combined to yield a greater increase in CO during upright movement. This greater central response coupled with the increased PP and LVC explains the twofold greater and more sustained increase in movement-induced hyperemia in the upright compared with supine position and has clinical implications for rehabilitative medicine.

Gender differences in β‐adrenoceptor system in cardiac hypertrophy due to arteriovenous fistula

This study was undertaken to determine alterations in the β-adrenoceptor (β-AR) signaling system in male and female rats at 4 weeks after the induction of arteriovenous (AV) fistula or shunt. AV shunt produced a greater degree of cardiac hypertrophy and larger increase in cardiac output in male than in female animals. Increases in plasma levels of norepinephrine and epinephrine (EPI) due to AV shunt were also higher in male than females. While no difference in the β(1)-AR affinity was seen in males and females, AV shunt induced increase in β(1)-AR density in female rats was higher than that in males. Furthermore, no changes in basal adenylyl cyclase (AC) V/VI mRNA levels were seen; however, the increase in EPI-stimulated AC activities was greater in AV shunt females than in males. AV shunt decreased myocardial β(1)-AR mRNA level in male rats and increased β(2)-AR mRNA level in female hearts; an increase in G(i)-protein mRNA was detected only in male hearts. Although GRK2 gene expression was increased in both sexes, an increase in GRK3 mRNA was seen only in AV shunt female rats. β-arrestin1 mRNA was elevated in females whereas β-arrestin 2 gene expression was increased in both male and female AV shunt rats. While these data demonstrate gender associated differences in various components of the β-AR system in cardiac hypertrophy due to AV shunt, only higher levels of plasma catecholamines may account for the greater increase in cardiac output and higher degree of cardiac hypertrophy in males.

Comparison of Inhaled Iloprost and Nitric Oxide in Patients With Pulmonary Hypertension During Weaning From Cardiopulmonary Bypass in Cardiac Surgery: A Prospective Randomized Trial

The objective of this study was to compare the efficacy of inhaled iloprost and nitric oxide (iNO) in reducing pulmonary hypertension (PHT) during cardiac surgery immediately after weaning from cardiopulmonary bypass (CPB). A prospective randomized study. A single-center university hospital. Forty-six patients with PHT (mean pulmonary artery pressure (mPAP) > or = 26 mmHg preoperatively at rest, after anesthesia induction, and at the end of CPB) scheduled to undergo cardiac surgery were enrolled. Patients were randomly allocated to receive iloprost (group A, n = 23) or iNO (group B, n = 23) during weaning from CPB. Heart rate, mean arterial pressure, central venous pressure, pulmonary artery pressure (PAP), pulmonary capillary wedge pressure, and left atrial pressure were recorded continuously. Iloprost and iNO were administered immediately after the end of CPB before heparin reversal. Both substances caused significant reductions in mean PAP (mPAP) and pulmonary vascular resistance (PVR) and significant increases in cardiac output 30 minutes after administration (p < 0.0001). However, in a direct comparison, iloprost caused significantly greater reductions in PVR (p = 0.013) and mPAP (p = 0.0006) and a significantly greater increase in cardiac output (p = 0.002) compared with iNO. PHT after weaning from CPB was significantly reduced by the selective pulmonary vasodilators iNO and iloprost. However, in a direct comparison of the 2 substances, iloprost was found to be significantly more effective.

Fructose ingestion acutely elevates blood pressure in healthy young humans

Overconsumption of fructose, particularly in the form of soft drinks, is increasingly recognized as a public health concern. The acute cardiovascular responses to ingesting fructose have not, however, been well-studied in humans. In this randomized crossover study, we compared cardiovascular autonomic regulation after ingesting water and drinks containing either glucose or fructose in 15 healthy volunteers (aged 21-33 yr). The total volume of each drink was 500 ml, and the sugar content 60 g. For 30 min before and 2 h after each drink, we recorded beat-to-beat heart rate, arterial blood pressure, and cardiac output. Energy expenditure was determined on a minute-by-minute basis. Ingesting the fructose drink significantly increased blood pressure, heart rate, and cardiac output but not total peripheral resistance. Glucose ingestion resulted in a significantly greater increase in cardiac output than fructose but no change in blood pressure and a concomitant decrease in total peripheral resistance. Ingesting glucose and fructose, but not water, significantly increased blood pressure variability and decreased cardiovagal baroreflex sensitivity. Energy expenditure increased by a similar amount after glucose and fructose ingestion, but fructose elicited a significantly greater increase in respiratory quotient. These results show that ingestion of glucose and fructose drinks is characterized by specific hemodynamic responses. In particular, fructose ingestion elicits an increase in blood pressure that is probably mediated by an increase in cardiac output without compensatory peripheral vasodilatation.

Cardiovascular responses in healthy young women during exposure to whole-body vibration

The effects of varied seating posture conditions on cardiovascular responses in healthy women were studied during exposure to whole-body vibration (WBV). After an assessment of upper-body fitness, 14 healthy young women were exposed to 3, 4.5, and 6 Hz (at 0.9 g r.m.s. in the vertical direction) on a vibration simulator for 3 separate days. Each day the protocol consisted of 6 min of baseline without WBV (control), 8 min of WBV exposure to a single frequency either ‘with’ or ‘without’ backrest, 4 min of recovery, followed by 8 min of WBV at the same frequency with opposite backrest condition, and 4 min of recovery. Cardiac output was estimated by using the carbon dioxide rebreathing technique during three conditions: (1) control; and before completion of WBV session of sitting (2) ‘with’; and (3) ‘without’ backrest during exposure to WBV. Statistical analysis revealed that pulmonary oxygen uptake responses were not influenced by the change in frequency but only by the posture. Although cardiac output reached equal levels during sitting ‘without’ backrest at 3 and 4.5 Hz ( P>0.05), the heart rate difference was significant between these frequencies ( P<0.05), suggesting the role of stroke volume in maintaining cardiac output. As heart rate responses were not significant at 4.5 and 6 Hz ( P>0.05), the greater increase in cardiac output ( P<0.05) during sitting ‘with’ backrest compared to the control condition, can be attributed to decrease in stroke volume only. Based on the cardiovascular responses, it is speculated that the muscle pump in the legs is inactive during WBV exposure in the seated posture, thereby affecting stroke volume, especially at the spinal resonance frequency of 4.5 Hz. Overall, this study demonstrates that subjects exposed to WBV will experience greater metabolic responses compared to sitting without WBV, and these physiological responses during WBV resemble that of ‘light’ physical work. Relevance to industry Although, the risk of cardiovascular disease due to exposure to workplace WBV is still speculative, assessment of cardiovascular responses is important in improving the guidelines for human responses to vibration. Results from the present study are anticipated to further contribute to the understanding of the adverse health effects on human performance due to WBV.

Muscle metaboreflex-induced increases in cardiac sympathetic activity vasoconstrict the coronary vasculature

Ischemia of active skeletal muscle evokes a powerful blood pressure-raising reflex termed the muscle metaboreflex (MMR). MMR activation increases cardiac sympathetic nerve activity, which increases heart rate, ventricular contractility, and cardiac output (CO). However, despite the marked increase in ventricular work, no coronary vasodilation occurs. Using conscious, chronically instrumented dogs, we observed MMR-induced changes in arterial pressure, CO, left circumflex coronary blood flow (CBF), and coronary vascular conductance (CVC) before and after alpha1-receptor blockade (prazosin, 100 microg/kg iv). MMR was activated during mild treadmill exercise by partially reducing hindlimb blood flow. In control experiments, MMR activation caused a substantial pressor response-mediated via increases in CO. Although CBF increased (+28.1 +/- 3.7 ml/min; P < 0.05), CVC did not change (0.45 +/- 0.05 vs. 0.47 +/- 0.06 ml x min(-1) x mmHg(-1), exercise vs. exercise with MMR activation, respectively; P > 0.05). Thus all of the increase in CBF was due to the increase in arterial pressure. In contrast, after prazosin, MMR activation caused a greater increase in CBF (+55.9 +/- 17.1 ml/min; P < 0.05 vs. control) and CVC rose significantly (0.59 +/- 0.08 vs. 0.81 +/- 0.17 ml x min(-1) x mmHg(-1), exercise vs. exercise with MMR activation, respectively; P < 0.05). A greater increase in CO also occurred (+2.01 +/- 0.1 vs. +3.27 +/- 1.1 l/min, control vs. prazosin, respectively; P < 0.05). We conclude that the MMR-induced increases in sympathetic activity to the heart functionally restrain coronary vasodilation, which may limit increases in ventricular function.