Higher Stroke Volume Research Articles

Atrioventricular delay programming in cardiac resynchronization therapy devices: fixed or adaptive?: A randomized monocenter trial

IntroductionCardiac resynchronization therapy devices are routinely programmed on fixed atrioventricular delays (AVD) under resting conditions based on echocardiographic techniques. Whether this AVD also ensures optimal exercise hemodynamics, is unclear. MethodsIn order to compare fixed-AVD with rate-adaptive AVD, 100 patients with cardiac resynchronization therapy systems and sinus rhythm were randomized to fixed-AVD or adaptive-AVD. The patients then underwent bicycle ergometry with noninvasive hemodynamic monitoring. At rest and at peak exercise, stroke volume, cardiac output, and cardiac index were determined using “electrical velocimetry.” ResultsThere were no significant differences in clinical characteristics and baseline hemodynamic parameters between fixed or adaptive AVD. In patients randomized to adaptive AVD, a trend towards higher stroke volume, cardiac output, and cardiac index at peak exercise was encountered. ConclusionsBased on the trend towards better exercise hemodynamics demonstrated by this pilot study, a randomized follow-up study with clinical end points appears to be justified to clarify this issue.

Efectos de un programa de ejercicio físico supervisado sobre la estructura cardiaca durante la gestación. Ensayo clínico aleatorizado

ObjectiveTo analyze the safety of aerobic exercise for the cardiovascular system in pregnant women, and to assess improvement in the cardiovascular system. Subjects and methodsA randomized clinical trial was designed. Data collection was performed at weeks 20 and 34 of gestation. At week 20, 45 women were studied in the exercise (EG), of which 35 completed the study. There were 14 pregnant women in the control group (CG) in week 20, of which nine completed the study. ResultsAt week 20 there were improvements in body mass index (EG: 25.1.±.4.3/CG: 27.9±4.5) (P=.04), and in systolic blood pressure (EG: 104.7±10.9/CG: 112 .5±11.3) (P=.02). In the CG there was concentric hypertrophy (N=2; 14.3%). At week 34, the EG had a higher stroke volume (EG: 52.33±10.42/GC: 43.69±9.48) (P=.03). ConclusionAerobic exercise during pregnancy is safe for the cardiovascular system and even improves some parameters.

Infection after Acute Ischemic Stroke: Risk Factors, Biomarkers, and Outcome

Background. The activation of inflammatory cascades triggered by ischemic stroke may play a key role in the development of infections. Methods. Patients admitted with ischemic stroke within 24 hours were prospectively enrolled. Biomarkers of infection were measured on days 1, 3, and 5. The patients were continuously monitored for predefined infections. Results. Patients with infection were older (OR 1.06 per year, 95% CI 1.01–1.11) and had a higher National Institute of Health Stroke Scale Score (NIHSS, OR 1.21, 95% CI 1.10–1.34), localization in the insula, and higher stroke volumes on diffusion-weighted imaging. The maximum temperature on days 1 and 3, leukocytes, interleukin-6, lipopolysaccharide-binding protein on days 1, 3, and 5, C-reactive protein on days 3 and 5, and procalcitonin on day 5 were higher and HLA-DR-expression on monocytes on days 1, 3, and 5 lower in patients with infection. Age and NIHSS predicted the development of infections. Infection was an independent predictor of poor functional outcome. Conclusions. Severe stroke and increasing age were shown to be early predictors for infections after stroke.

Altered hemodynamic regulation and reflex control during exercise and recovery in obese boys

The aims of the present study were to assess in obese and lean boys 1) the hemodynamic responses and baroreflex sensitivity (BRS) to isometric handgrip exercise (HG) and recovery and 2) the muscle metaboreflex-induced blood pressure response and the variables that determine this response. Twenty-seven boys (14 obese and 13 lean boys, body mass index: 29.2 ± 0.9 vs. 18.9 ± 0.3 kg/m(2), respectively) participated. The testing protocol involved 3 min of baseline, 3 min of HG (30% maximum voluntary contraction), 3 min of circulatory occlusion, and 3 min of recovery. The same protocol was repeated without occlusion. At baseline, no differences were detected between groups in beat-to-beat arterial pressure (AP), heart rate (HR), and BRS; however, obese boys had higher stroke volume and lower total peripheral resistance than lean boys (P < 0.05). During HG, lean boys exhibited higher HR and lower BRS compared with their obese counterparts. In lean boys, BRS decreased during HG compared with baseline, whereas in obese boys, it was not significantly modified. In lean boys, TPR was elevated during HG and declined after exercise, whereas in obese boys, TPR did not significantly decrease after exercise cessation. In the postexercise period, BRS in lean boys returned to baseline, whereas an overshoot was observed in obese boys. Postexercise BRS was correlated with body mass index (R = 0.56, P < 0.05). Although the metaboreflex-induced increase in AP was similar between obese and lean children, it was achieved via different mechanisms: in lean children, total peripheral resistance was the main contributor to AP maintenance during the metaboreflex, whereas in obese children, stroke volume significantly contributed to AP maintenance during the metaboreflex. In conclusion, obese normotensive children demonstrated altered cardiovascular hemodynamics and reflex control during exercise and recovery.

Cardiac output but not stroke volume is similar in a Wingate and $$ \dot{V}{\text{O}}_{{ 2 {\text{peak}}}} $$ test in young men

Wingate test (WT) training programmes lasting 2-3weeks lead to improved peak oxygen consumption. If a single 30s WT was capable of significantly increasing stroke volume and cardiac output, the increase in peak oxygen consumption could possibly be explained by improved oxygen delivery. Thus, we investigated whether a single WT increases stroke volume and cardiac output to similar levels than those obtained at peak exercise during a graded cycling exercise test (GXT) to exhaustion. Fifteen healthy young men (peak oxygen consumption 45.0±5.3mlkg(-1)min(-1)) performed one WT and one GXT on separate days in randomised order. During the tests, we estimated cardiac output using inert gas rebreathing (nitrous oxide and sulphur hexafluoride) and subsequently calculated stroke volume. We found that cardiac output was similar (18.2±3.3 vs. 17.9±2.6lmin(-1); P=0.744), stroke volume was higher (127±37 vs. 94±15ml; P<0.001), and heart rate was lower (149±26 vs. 190±12 beatsmin(-1); P<0.001) at the end (27±2s) of a WT as compared to peak exercise during a GXT. Our results suggest that a single WT produces a haemodynamic response which is characterised by similar cardiac output, higher stroke volume and lower heart rate as compared to peak exercise during a GXT.

Nervous and humoral catecholaminergic control of blood pressure and cardiac performance in the Antarctic fish Pagothenia borchgrevinki

The role of circulating and neural catecholamines for cardiovascular control in the Antarctic fish Pagothenia borchgrevinki was studied in vivo using pharmacological tools and with immunohistochemistry on isolated tissues. Adrenergic nerve blockade with bretylium decreased dorsal aortic pressure (P(da)) and systemic vascular resistance (R(sys)), while cardiac output (Q) did not change. The blockade of alpha-adrenoceptors with phentolamine reduced P(da) and R(sys) further, revealing that vasomotor tone was influenced by circulating catecholamines in bretylium treated fish. The physiological evidence for an adrenergic nervous control of the vasculature was corroborated by the presence of tyrosine hydroxylase (TH)-immunoreactive fibres associated with blood vessels in spleen, gonads and gastrointestinal tract. TH-immunoreactive fibres were not observed in the atrium and ventricle, but a dense population of TH-immunoreactive fibres was apparent in the bulbus arteriosus. The present study suggests that an adrenergic nervous mechanism is responsible for maintaining vasomotor tone in P. borchgrevinki. While experiments failed to demonstrate a tonic adrenergic nervous influence affecting cardiac performance, an adrenergic nervous control of bulbar compliance may be essential for optimizing gill blood flow dynamics in this species, which has a high relative stroke volume and displays profound changes in stroke volume in vivo.

Effects of Acute Hypoxia at Moderate Altitude on Stroke Volume and Cardiac Output During Exercise

It has been unclear how acute hypoxia at moderate altitude affects stroke volume (SV), an index of cardiac function, during exercise. The present study was conducted to reveal whether acute normobaric hypoxia might alter SV during exercise.Nine healthy male subjects performed maximal exercise testing under normobaric normoxic, and normobaric hypoxic conditions (O(2): 14.4%) in a randomized order. A novel thoracic impedance method was used to continuously measure SV and cardiac output (CO) during exercise. Acute hypoxia decreased maximal work rate (hypoxia; 247 + or - 6 [SE] versus normoxia; 267 + or - 8 W, P < 0.005) and VO(2) max (hypoxia; 2761 + or - 99 versus normoxia; 3039 + or - 133 mL/min, P < 0.005). Under hypoxic conditions, SV and CO at maximal exercise decreased (SV: hypoxia; 145 + or - 11 versus normoxia; 163 + or - 11 mL, P < 0.05, CO: hypoxia; 26.7 + or - 2.1 versus normoxia; 30.2 + or - 1.8 L/min, P < 0.05). In acute hypoxia, SV during submaximal exercise at identical work rate decreased. Furthermore, in hypoxia, 4 of 9 subjects attained their highest SV at maximal exercise, while in normoxia, 8 of 9 subjects did.Acute normobaric hypoxia attenuated the increment of SV and CO during exercise, and SV reached a plateau earlier under hypoxia than in normoxia. Cardiac function during exercise at this level of acute normobaric hypoxia might be attenuated.

Cardiac output and oxygen uptake relationship during physical effort in men and women over 60 years old

This study investigated the relationship between oxygen uptake (VO(2)), cardiac output (Q), stroke volume (SV), and heart rate (HR) in 54 men and 77 women (age = 69 +/- 5 years) during incremental effort. Subjects performed a maximal cycle-ergometer test and VO(2) was directly measured. HR and SV were assessed by ECG and cardiograph impedance. Regression equations were calculated for Q-VO(2), HR-VO(2), and Q-HR relationships. The equations obtained for women were (a) Q (l min(-1)) = 2.61 + 4.67 VO(2) (l min(-1))(r(2) = 0.84); (b) HR (bpm) = 62.03 + 46.55 VO(2) (l min(-1)) (r (2) = 0.72); (c) SV (ml) 100:6[1 - e(-2.6 VO2 (1 min-1))] (r (2) = 0.41); (d) HR (bpm) = 41.48 + 9.24 Q (l min(-1)) (r (2) = 0.73). Equations for men were (a) Q (l min(-1)) = 2.52 + 5.70 VO(2) (l min(-1)) (r (2) = 0.89); (b) HR (bpm) = 66.31 + 32.35 VO(2) (l min(-1)) (r (2) = 0.72); (c) [1 - e(-1.7 VO2 (1 min-1))] (r (2) = 0.47); (d) HR (bpm) = 56.33 + 5.25 Q (l min(-1)) (r (2) = 0.69). The intercepts for Q-VO(2) and HR-VO(2) equations were similar for both genders, but the slopes were different (P < 0.05). The SV increased from baseline to 50-60% of VO(2) peak in both groups. No gender effect was found in SV increasing pattern, but the absolute values were in general higher for men (P > 0.05). A significant difference between men and women was observed for both slopes and intercepts in the Q-HR relationship (P < 0.05). In conclusion, (a) Q-VO(2) relation was linear during progressive effort; (b) regression intercepts were similar, but the slopes were higher for men compared to women; (c) SV-VO(2) relationship was nonlinear and maximum SV was reached at very submaximal workload; (d) older men exhibited higher Q upward potential as well higher SV but lower HR for a given submaximal workload than women of similar age.

Cardiac response to exercise in young, normal weight and overweight men and women

Overweight and obesity are associated with hemodynamic changes at rest. Whether these changes are mirrored during exercise is uncertain. We compared cardiac output (Q) and stroke volume (SV) in 12 overweight (OW) and 12 normal weight (NW) adults at rest and during exercise. Participants were assessed for body composition, peak oxygen consumption, and Q and SV at rest and during cycling exercise at 50, 75 and 100 W. Cardiac output was significantly higher at rest and during exercise in OW than NW when fat mass and ethnicity were used as covariates. When fat free mass was added as a covariate, Q was no longer different between groups. Stroke volume tended to be higher in OW than NW when fat mass and ethnicity were used as covariates (P = 0.055) with no differences in heart rate observed. Although the total change in Q and SV was similar between groups with each exercise intensity, overall Q was higher in the OW than NW participants. The higher Q is likely explained by a higher SV, secondary to a greater blood volume in the OW. The elevated hemodynamic response in OW may reflect the early cardiac adaptations of excess body mass.

Left atrial systolic force in hypertensive patients with left ventricular hypertrophy: the LIFE study

In hypertensive patients without prevalent cardiovascular disease, enhanced left atrial systolic force is associated with left ventricular hypertrophy and increased preload. It also predicts cardiovascular events in a population with high prevalence of obesity. Relations between left atrial systolic force and left ventricular geometry and function have not been investigated in high-risk hypertrophic hypertensive patients. Participants in the Losartan Intervention For Endpoint reduction in hypertension echocardiography substudy without prevalent cardiovascular disease or atrial fibrillation (n = 567) underwent standard Doppler echocardiography. Left atrial systolic force was obtained from the mitral orifice area and Doppler mitral peak A velocity. Patients were divided into groups with normal or increased left atrial systolic force (>14.33 kdyn). Left atrial systolic force was high in 297 patients (52.3%), who were older and had higher body mass index and heart rate (all P < 0.01) but similar systolic and diastolic blood pressure, in comparison with patients with normal left atrial systolic force. After controlling for confounders, increased left atrial systolic force was associated with larger left ventricular diameter and higher left ventricular mass index (both P < 0.01). Prevalence of left ventricular hypertrophy was greater (84 vs. 64%; P < 0.001). Participants with increased left atrial systolic force exhibited normal ejection fraction; higher stroke volume, cardiac output, transmitral peak E velocities and peak A velocities; and lower E/A ratio (all P < 0.01). Enhanced left atrial systolic force identifies hypertensive patients with greater left ventricular mass and prevalence of left ventricular hypertrophy, but normal left ventricular chamber systolic function with increased transmitral flow gradient occurring during early filling, consistent with increased preload.

Temperature tolerance of Zoea I from two different populations of the kelp crab Taliepus dentatus

Thermal tolerance of single larval stages has rarely been studied, eventhough the larva might be the actual physiological bottleneck of all life history stages setting distribution limits. Therefore, temperature tolerance of Zoea I was examined in two different population of the Chilean kelp crab Taliepus dentatus. We measured activity, oxygen consumption, cardiac performance and the CN composition of larval T. dentatus of two populations from central and southern Chile at various temperatures (1) to determine at which organisational level T. dentatus larvae get first affected by temperature, integrating variables from the organismal, tissue functional to the biochemical elemental level, and (2) to compare the thermal tolerance of larvae from varying environmental temperature regimes to look at functional differences between populations as a correlate of adaptation capacities of the Zoea. Our mechanistic analysis explicitly sheds light on how temperature affects the physiology of crab larvae. We found that the highest organisational level gets affected first, seen in activity decrements at unsuitably high or low temperatures, paralleled by decreases in oxygen consumption rates. Cardiac performance is more robust to temperature changes. Heart beat rate decreases only at very high and low temperature extremes and stroke volume is almost temperature independent. The comparison between the southern and central populations showed a limited but clear adaptation of larvae from the southern sampling site to the colder environmental temperature regime, visible at all organisational levels.

EPINEPHRINE VERSUS DOPAMINE TO TREAT SHOCK IN HYPOXIC NEWBORN PIGS RESUSCITATED WITH 100% OXYGEN

Shock and tissue hypoperfusion are common after asphyxia. We compared systemic and regional hemodynamic effects of epinephrine and dopamine in the treatment of shock and hypotension in asphyxiated newborn piglets resuscitated with 100% oxygen. Twenty-four piglets (1-3 days old; weight, 1.4-2.6 kg) were acutely instrumented to measure cardiac index (CI), carotid, mesenteric and renal arterial blood flows, and mean systemic (SAPs) and pulmonary arterial pressures (PAPs). Piglets had normocapnic alveolar hypoxia (F(IO2)=0.08-0.10) for 50 min and reoxygenated with F(IO2)=1.0 for 1 h then F(IO2)=0.21 for 3.5 h. After 2 h reoxygenation, either dopamine (2 microg kg(-1) min(-1)) or epinephrine (0.2 microg kg(-1) min(-1)) was given for 30 min in a blinded randomized manner, which was then increased to maintain SAP (within 10% of baseline, pressure-driven dose) for 2 h. Hypoxia caused hypotension (SAP, 44%+/-3% of baseline), cardiogenic shock (CI, 41%+/-4%), and metabolic acidosis (mean pH, 7.04-7.09). Upon reoxygenation, hemodynamic parameters immediately recovered but gradually deteriorated during 2 h with SAP at 45+/-1 mmHg, CI at 74+/-9% of baseline, and pH 7.32+/-0.03. Low doses of either drug had no significant systemic and renal hemodynamic response. Epinephrine (0.3-1.5 microg kg(-1) min(-1)) for 2 h increased SAP and CI (with higher stroke volume) and decreased pulmonary vascular resistance (with reduced PAP-SAP ratio), whereas the responses with dopamine (10-25 microg kg(-1) min(-1)) were modest. Low-dose epinephrine improved mesenteric and carotid arterial flows, whereas the pressure-driven doses of epinephrine and dopamine increased carotid and mesenteric arterial flows, respectively. To treat shock in asphyxiated newborn piglets resuscitated with 100% oxygen, epinephrine exhibits an inotropic action compared with dopamine, whereas both catecholamines can increase carotid and mesenteric perfusion.

FLUID RESUSCITATION IN SEVERE SEPSIS AND SEPTIC SHOCK

The aim of this study was to investigate whether the type of i.v. fluid administered has an impact on outcome in an animal model of septic shock. The study included 28 anesthetized, invasively monitored, mechanically ventilated female sheep (29.5 +/- 4.0 kg), which received 0.5 g/kg body weight of feces into the abdominal cavity to induce peritonitis. During the surgical operation and 4 h after feces spillage, only Ringer's lactate (RL) was administered in all animals. Thereafter, animals were randomized to receive continuous infusions of RL (n = 7) alone or combined with either 20% albumin (n = 7, volume ratio to RL 1:10) or 6% hydroxyethyl starch (HES) (n = 7, volume ratio to RL 1:1), or gelatin alone (n= 7, no volume limitation). Fluid resuscitation was titrated to maintain pulmonary artery occlusion pressure at baseline levels throughout the experiment. No antibiotics or vasoactive drugs were administered, and animals were monitored until their spontaneous death. Hemodynamic variables were better with HES and albumin than with the other fluids, as reflected by higher stroke volume, cardiac index, and oxygen delivery (all P < 0.05). Hydroxyethyl-starch-treated animals also had lower arterial lactate concentrations (P < 0.01). However, times to develop hypotension and oliguria were similar in all groups. Blood interleukin (IL) 6 concentrations were significantly increased in all groups. The mean survival time was similar in all groups. In this clinically relevant model of prolonged septic shock, albumin and HES solution resulted in higher cardiac output, oxygen delivery, and lower blood lactate levels than gelatin and RL; however, the choice of i.v. fluid did not affect outcome.

Clinical Comparison Between HeartMate VE Auto-Mode and HeartMate XVE Auto-Mode With Opti-Fill and the Effect of Stroke Volume on Blood Chamber and Inflow Valve Peak Pressures

We determined the difference between HeartMate (HM) VE auto mode, average filling 76 mL, and HM XVE Opti-Fill, average filling 79 mL, regarding blood chamber and inflow valve peak pressure pulses (BCPP and IVPP). The relation between stroke volume (SV) and peak pressures was investigated by using a circulatory mock loop. At high SVs, 79 to 83 mL, BCPP and IVPP never exceeded 400 mm Hg. For lower SVs, down to 50 mL, the peak pressures increased to 788 mm Hg for BCPP and 416 mm Hg for IVPP. Distribution of SV was measured in 2 VE and 6 XVE patients during rest and activities of daily living (ADL). For clinical comparison, percentages of SV >78 mL were determined. At rest, 2190 (VE) and 5772 (XVE) pump beats were registered and 4511 (VE) and 8713 (XVE) during ADL. Percentages of "SV >78 mL" at rest, respectively, were 42.5 +/- 3.5 and 78.2 +/- 4.7 (p < 0.01) and during ADL, respectively, 48.7 +/- 7.4 and 73.5 +/- 5.3 (p < 0.01). The Opti-Fill software shows a significant increase in percentage SV >78 mL and makes an important contribution to reducing the incidence of high peak pressures in the clinical setting.

Mechanical Heart Valve Performance in a Pulsatile Pediatric Ventricular Assist Device

A pulsatile pediatric ventricular assist device with a dynamic stroke volume of 12 ml is currently under development at the Pennsylvania State University. A monoleaflet valve (Björk-Shiley Monostrut) and a bileaflet valve (CPHV, CarboMedics Prosthetic Heart Valve) were examined in this study. A high-speed video and data acquisition system was used to simultaneously record video images, pressure waveforms, and flow waveforms for an array of in vitro test conditions that varied heart rate and systolic duration. The CPHV in both the horizontal and vertical orientations have larger regurgitant volumes than the Monostrut valves at all operating conditions in both the inlet and outlet positions. However, the CPHV has higher stroke volumes and cardiac outputs than the Monostrut valve at higher heart rates and longer systolic durations. In addition, the hydrodynamic performance of the Monostrut valve is more sensitive to changes in operating conditions for the pulsatile pediatric ventricular assist device than the CPHV in both orientations. Additional testing is under way to identify the optimal operating conditions for each type of valve.

NOS3 Gene Polymorphisms and Exercise Hemodynamics in Postmenopausal Women

We tested whether the G894T and T-786C NOS3 polymorphisms were associated with exercise cardiovascular (CV) hemodynamics in sedentary, physically active, and endurance-trained postmenopausal women. CV hemodynamic parameters including heart rate (HR), systolic (SBP) and diastolic (DBP) blood pressures and cardiac output (Q), as determined by acetylene rebreathing, stroke volume (SV), arteriovenous oxygen difference (a-vO2 diff), and total peripheral resistance (TPR) were measured during submaximal (40, 60, 80 %) and maximal (approximately 100 % VO2max) exercise. NOS3 G894T genotype was not significantly associated, either independently or interactively with habitual physical activity (PA) level, with SBP, Q, TPR, or a-vO2 diff during submaximal or maximal exercise. However, NOS3 894T non-carriers had a higher submaximal exercise HR than NOS3 894T allele carriers (120 +/- 2 vs. 112 +/- 2 beats/min, p = 0.007). NOS3 894T allele carriers had a higher SV than 894T non-carriers (78 +/- 2 vs. 72 +/- 2 ml/beat, p = 0.03) during submaximal exercise. NOS3 894T non-carriers also had a higher maximal exercise HR averaged across habitual PA groups than T allele carrier women (165 +/- 2 vs. 158 +/- 2 beats/min, p = 0.04). NOS3 894T allele carriers also tended to have a higher SV during maximal exercise than 894T non-carriers (70 +/- 2 vs. 64 +/- 2 ml/beat, p = 0.08). NOS3 T-786C genotype was not significantly associated, either independently or interactively, with any of the CV hemodynamic measures during submaximal or maximal exercise. These results suggest an association of NOS3 G894T genotype with submaximal and maximal exercise CV hemodynamic responses, especially HR, in postmenopausal women.

Spurious systolic hypertension in youth: what does it really mean in clinical practice?

In clinical practice, brachial blood pressure measurement remains the classical reference for identifying hypertension, but this has been challenged recently. Indeed, estimation of central aortic pressure has been shown to be a stronger predictor of coronary artery disease [1,2] and even brings new insights regarding the effect of different antihypertensive drugs, as documented in the Conduit Artery Function Evaluation (CAFE) study. CAFE is a sub-study of the large Anglo-Scandinavian Cardiac Outcomes trial (ASCOT) in which, despite the similar control of brachial blood pressure, aortic blood pressure was significantly lower in the amlodipine-perindopril arm compared to the betablocker-diuretic arm [3,4].

WISE‐2005: Adrenergic responses to 60 days of 6o head‐down bed‐rest (BR) in women with exercise counter‐measures

Women are especially susceptible to orthostatic intolerance on return from space or after BR. Before and after 2 doses of isoproterenol (ISO) or norepinephrine (NOR) MAP, HR, cardiac output (Q), stroke volume (SV), and total peripheral resistance (TPR) were measured in 8 controls and 8 women with flywheel and lower body negative pressure treadmill exercise (EX). Pre-BR, ISO2 caused: higher HR, higher SV, higher Q, and lower TPR. NOR2 caused: lower SV, lower Q, higher TPR and higher MAP. Post-BR controls show higher baseline HR (64.9 ± 2.3 to 72.5 ± 4.8 bpm) and no increase in MAP due to NOR1. Post-BR EX show no increase of baseline HR, higher baseline TPR (18.0 ± 2.1 to 20.2 ± 2.8 mmHg/mL/min), reduced baseline Q (5.5 ± 0.5 mL/min to 4.5 ± 0.5 mL/min), reduced Q with ISO2 (Pre: 8.6 ± 0.9 mL/min; Post: 7.5 ± 0.8 mL/min), augmented TPR with NOR1 (Pre: 19.4 ± 2.2 mmHg; Post: 23.7 ± 3.3 mmHg). Controls show decreased peripheral and increased cardiac sensitivity of adrenergic receptors. EX show increased peripheral sensitivity without cardiac augmentation. We conclude that exercise is cardioprotective after exposure to 60-day BR (CSA, NASA, ESA & CNES).

Vascular calcification and cardiovascular function in chronic kidney disease

Vascular calcification and arterial stiffening are independent predictors of all causes and cardiovascular mortality in chronic kidney disease (CKD). Few data are currently available comparing vascular calcification and its attendant functional cardiovascular consequences between CKD stage 4 patients and both peritoneal dialysis (PD) and haemodialysis (HD) (CKD stage 5) patients. We studied 134 subjects (60 HD, 28 PD and 46 CKD 4). Vascular calcification was quantified using multi-slice spiral CT scanning of a 5 cm standardized segment of superficial femoral artery. Pulse wave analysis and pulse wave velocity were assessed using applanation tonometry, to determine arterial compliance. Further digital arterial pulse wave analysis was used to measure systemic haemodynamic variables. All medications were recorded and biochemical variables were time averaged for the 6 months prior to entering the study. Forty-seven percent of CKD 4 patients demonstrated vascular calcification as compared with CKD 5 (71% PD and 73% HD, P = 0.02). HD patients had higher calcification scores (median 121) than either PD (median 21) or CKD 4 (median 0) (P = 0.008). There were no significant differences in baseline characteristics between the groups. Comparing tertiles of patients (based on calcification score), increased calcification score was associated with a reduction in arterial compliance (mean PWV 8.9 +/- 1.1, 11 +/- 3.6, 11.3 +/- 3.7 m/s, P = 0.005). The degree of calcification did not influence systolic blood pressure (BP), diastolic BP or heart rate. However, more heavily calcified patients demonstrated significantly higher mean pulse pressures (58 +/- 19, 74 +/- 22 and 72 +/- 25 mmHg, P = 0.001), lower total peripheral resistance (1.5 +/- 1, 1.3 +/- 0.8, 0.9 +/- 0.4, P = 0.01) and higher stroke volume (84 +/- 25, 95 +/- 29, 106 +/- 39 ml, P = 0.01). More heavily calcified patients were significantly older and predominantly male. This study has successfully utilized a novel technique for the quantification of calcification. We have demonstrated vascular calcification and associated cardiovascular dysfunction in CKD 4, PD and HD with significant differences between the groups. Thirty percent of individuals show no calcification, even those established on renal replacement therapy for a prolonged period of time. Further work is required to identify factors which promote progression of arterial calcification in those who are susceptible.

Accuracy of 3-Dimensional Color Doppler-Derived Flow Volumes With Increasing Image Depth

We and others have reported on the use of digital color Doppler sonography from real-time 3-dimensional (3D) echocardiography and its use in accurately calculating cardiac flow volumes, namely stroke volume (SV) and, hence, cardiac output. However, in some patients, image depth is higher than average, and this may affect the accuracy of volume calculation. We sought to investigate the impact of image depth and the accompanying change in signal strength, spatial resolution, and pulse repetition frequency on the accuracy of SV calculation from 3D color Doppler data in an in vitro model. A tube model of the left ventricular outflow tract was constructed from plastic tubing and connected to a pulsatile pump. The volume flowing through the tube was imaged using a 3D echocardiography system. Stroke volumes from the pump were computed from the DICOM data using commercially available software and compared with a reference standard of timed volumes with the use of a graduated measuring cylinder over a range of depth settings and SVs. There was good correlation between the 3D-derived SVs and the reference cylinder measures over all depths from 4 to 16 cm at 1-cm increments with a tube diameter of 17 mm, a pump rate of 60 beats/min, and SVs ranging from 20 to 70 mL. The average r(2) value for the 13 different depths was 0.976. However, the accuracy of the 3D method of volume calculation appeared to fall at depths greater than 13 cm, especially at higher SVs. Stroke volume calculation from real-time 3D color Doppler data in this in vitro study shows that at depths greater than approximately 13 cm, accuracy decreases, especially at higher SVs. This may be due to decreased resolution and the reduced frame rate at these depths. At shallower depths, volume calculation form the 3D Doppler data appears very accurate.