Stroke volume (SV), heart rate (HR) and arterio-venous O2 difference (a-vO2diff) responses to heavy and severe-intensity exercise have been well documented; however, there is a lack of information on the SV, HR and a v-O2diff responses of work rates within extreme exercise domain. The aim of this study was, therefore, to focus on central and peripheral components of VO2 responses to exercises performed within the heavy, severe and extreme exercise domain. Eight well-trained male cyclists participated in this study. Maximal O2 consumption (VO2max) and corresponding work rate (P@VO2max) were determined by multisession constant work rate exercises. Cardiovascular responses to exercises were evaluated by nitrous-oxide rebreathing method with work rates from 40 % to 160 % of P@VO2max, VO2max corresponded to 324+/-39.4 W; however, maximal SV responses occurred at 205+/-54.3 W (p<0.01). Maximal cardiac output (Q), HR, and a vO2diff responses were revealed by the P@VO2max. VO2 response to exercise significantly decreased from severe-intense exercises to the first work rate of extreme exercise domain due to significant decreases in Q, SV, and HR responses (p<0.05), except a v-O2diff (p>0.05). Moreover, non-significant decreases in Q, SV, and a v-O2diff were evaluated as response to increase in work rate belonging to extreme work rates (p>0.05), except the HR (p<0.05). Work rates within the lower district of the extreme exercise domain have an important potential to improve peripheral component of VO2, while the P@VO2max seems the most appropriate intensity for aerobic endurance development as it maximizes the central component of VO2max.

• MeSH
• cvičení * fyziologie   MeSH
• lidé MeSH
• minutový srdeční výdej fyziologie   MeSH
• spotřeba kyslíku * fyziologie   MeSH
• srdeční frekvence MeSH
• tepový objem fyziologie   MeSH
• terapie cvičením MeSH
• zátěžový test MeSH
• Check Tag
• lidé MeSH
• mužské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH

BACKGROUND: Mechanical ventilation induces changes in intrapleural, intrathoracic and intra-abdominal pressure. These changes have various implications on cardiac output (CO). AIMS: The aim of this study was to determine the feasibility of measuring changes in CO after elective extubation in neonates using the principle of transthoracic bioreactance (TBR). STUDY DESIGN: This was a prospective observational cohort study in a level III neonatal centre. CO, stroke volume (SV) and heart rate were measured continuously for 2 h before and 2 h after elective extubation by TBR. SUBJECTS: Neonates undergoing elective extubation were eligible for enrolment. OUTCOME MEASURES: The primary outcome of the study was change in CO post elective extubation. RESULTS: Ten neonates were enrolled, seven (70 %) had a statistically significant decrease in CO after extubation, three (30 %) infants had a statistically significant increase in CO after extubation. Changes in CO were primarily driven by changes in SV and the pattern of change was related to patent ductus arteriosus (PDA) status prior to extubation. CONCLUSION: Extubation significantly influences CO in neonatal patients and the pattern of change appears to be related to PDA status.

• MeSH
• extubace * MeSH
• lidé MeSH
• minutový srdeční výdej fyziologie   MeSH
• novorozenec MeSH
• otevřená tepenná dučej * MeSH
• prospektivní studie MeSH
• studie proveditelnosti MeSH
• Check Tag
• lidé MeSH
• novorozenec MeSH
• Publikační typ
• časopisecké články MeSH
• pozorovací studie MeSH

During general anesthesia (GA), direct analysis of arterial pressure or aortic flow waveforms may be inconclusive in complex situations. Patient-specific biomechanical models, based on data obtained during GA and capable to perform fast simulations of cardiac cycles, have the potential to augment hemodynamic monitoring. Such models allow to simulate Pressure-Volume (PV) loops and estimate functional indicators of cardiovascular (CV) system, e.g. ventricular-arterial coupling (Vva), cardiac efficiency (CE) or myocardial contractility, evolving throughout GA. In this prospective observational study, we created patient-specific biomechanical models of heart and vasculature of a reduced geometric complexity for n = 45 patients undergoing GA, while using transthoracic echocardiography and aortic pressure and flow signals acquired in the beginning of GA (baseline condition). If intraoperative hypotension (IOH) appeared, diluted norepinephrine (NOR) was administered and the model readjusted according to the measured aortic pressure and flow signals. Such patients were a posteriori assigned into a so-called hypotensive group. The accuracy of simulated mean aortic pressure (MAP) and stroke volume (SV) at baseline were in accordance with the guidelines for the validation of new devices or reference measurement methods in all patients. After NOR administration in the hypotensive group, the percentage of concordance with 10% exclusion zone between measurement and simulation was >95% for both MAP and SV. The modeling results showed a decreased Vva (0.64±0.37 vs 0.88±0.43; p = 0.039) and an increased CE (0.8±0.1 vs 0.73±0.11; p = 0.042) in hypotensive vs normotensive patients. Furthermore, Vva increased by 92±101%, CE decreased by 13±11% (p < 0.001 for both) and contractility increased by 14±11% (p = 0.002) in the hypotensive group post-NOR administration. In this work we demonstrated the application of fast-running patient-specific biophysical models to estimate PV loops and functional indicators of CV system using clinical data available during GA. The work paves the way for model-augmented hemodynamic monitoring at operating theatres or intensive care units to enhance the information on patient-specific physiology.

• MeSH
• algoritmy MeSH
• arteriální tlak fyziologie   MeSH
• biomechanika MeSH
• celková anestezie metody   MeSH
• hemodynamické monitorování metody   MeSH
• hypotenze farmakoterapie   patofyziologie   MeSH
• krevní tlak MeSH
• lidé středního věku MeSH
• lidé MeSH
• minutový srdeční výdej fyziologie   MeSH
• modely kardiovaskulární * MeSH
• noradrenalin aplikace a dávkování   MeSH
• ověření koncepční studie MeSH
• prospektivní studie MeSH
• tepový objem fyziologie   MeSH
• vazokonstriktory aplikace a dávkování   MeSH
• Check Tag
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

• MeSH
• diagnostické techniky kardiovaskulární klasifikace   MeSH
• fetální krev fyziologie   MeSH
• fetální srdce fyziologie   MeSH
• foramen ovale apertum diagnostické zobrazování   patologie   terapie   MeSH
• foramen ovale abnormality   diagnostické zobrazování   patologie   MeSH
• lidé MeSH
• minutový srdeční výdej fyziologie   MeSH
• myokard MeSH
• nemoci nedonošenců * diagnostické zobrazování   patologie   terapie   MeSH
• novorozenec nedonošený MeSH
• novorozenec MeSH
• otevřená tepenná dučej diagnostické zobrazování   patologie   terapie   MeSH
• plicní hypertenze MeSH
• syndrom přetrvávajícího fetálního oběhu diagnóza   klasifikace   terapie   MeSH
• vrozené srdeční vady * diagnostické zobrazování   patologie   terapie   MeSH
• Check Tag
• lidé MeSH
• novorozenec MeSH
• Publikační typ
• přehledy MeSH

BACKGROUND: Continuous, reliable evaluation of left ventricular (LV) contractile function in patients with advanced heart failure requiring intensive care remains challenging. Continual monitoring of dP/dtmax from the arterial line has recently become available in hemodynamic monitoring. However, the relationship between arterial dP/dtmax and LV dP/dtmax remains unclear. This study aimed to determine the relationship between arterial dP/dtmax and LV dP/dtmax assessed using echocardiography in patients with acute heart failure. METHODS: Forty-eight patients (mean age 70.4 years [65% male]) with acute heart failure requiring intensive care and hemodynamic monitoring were recruited. Hemodynamic variables, including arterial dP/dtmax, were continually monitored using arterial line pressure waveform analysis. LV dP/dtmax was assessed using continuous-wave Doppler analysis of mitral regurgitation flow. RESULTS: Values from continual arterial dP/dtmax monitoring were significantly correlated with LV dP/dtmax assessed using echocardiography (r = 0.70 [95% confidence interval (CI) 0.51-0.82]; P < 0.0001). Linear regression analysis revealed that LV dP/dtmax = 1.25 × (arterial dP/dtmax) (P < 0.0001). Arterial dP/dtmax was also significantly correlated with stroke volume (SV) (r = 0.63; P < 0.0001) and cardiac output (CO) (r = 0.42; P = 0.0289). In contrast, arterial dP/dtmax was not correlated with SV variation, dynamic arterial elastance, heart rate, systemic vascular resistance (SVR), or mean arterial pressure. Markedly stronger agreement between arterial and LV dP/dtmax was observed in subgroups with higher SVR (N = 28; r = 0.91; P < 0.0001), lower CO (N = 26; r = 0.81; P < 0.0001), and lower SV (N = 25; r = 0.60; P = 0.0014). A weak correlation was observed in the subjects with lower SVR (N = 20; r = 0.61; P = 0.0004); in the subgroups with higher CO (N = 22) and higher SV (N = 23), no significant correlation was found. CONCLUSION: Our results suggest that in patients with acute heart failure requiring intensive care with an arterial line, continuous calculation of arterial dP/dtmax may be used for monitoring LV contractility, especially in those with higher SVR, lower CO, and lower SV, such as in patients experiencing cardiogenic shock. On the other hand, there was only a weak or no significant correlation in the subgroups with higher CO, higher SV, and lower SVR.

• MeSH
• dopplerovská echokardiografie metody   MeSH
• funkce levé komory srdeční fyziologie   MeSH
• kontrakce myokardu fyziologie   MeSH
• lidé středního věku MeSH
• lidé MeSH
• minutový srdeční výdej fyziologie   MeSH
• pilotní projekty MeSH
• senioři nad 80 let MeSH
• senioři MeSH
• srdeční frekvence fyziologie   MeSH
• srdeční selhání diagnostické zobrazování   patofyziologie   MeSH
• Check Tag
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• senioři nad 80 let MeSH
• senioři MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH

Recently, mathematical models of human integrative physiology, derived from Guyton's classic 1972 model of the circulation, have been used to investigate potential mechanistic abnormalities mediating salt sensitivity and salt-induced hypertension. We performed validation testing of 2 of the most evolved derivatives of Guyton's 1972 model, Quantitative Cardiovascular Physiology-2005 and HumMod-3.0.4, to determine whether the models accurately predict sodium balance and hemodynamic responses of normal subjects to increases in salt intake within the real-life range of salt intake in humans. Neither model, nor the 1972 Guyton model, accurately predicts the usual changes in sodium balance, cardiac output, and systemic vascular resistance that normally occur in response to clinically realistic increases in salt intake. Furthermore, although both contemporary models are extensions of the 1972 Guyton model, testing revealed major inconsistencies between model predictions with respect to sodium balance and hemodynamic responses of normal subjects to short-term and long-term salt loading. These results demonstrate significant limitations with the hypotheses inherent in the Guyton models regarding the usual regulation of sodium balance, cardiac output, and vascular resistance in response to increased salt intake in normal salt-resistant humans. Accurate understanding of the normal responses to salt loading is a prerequisite for accurately establishing abnormal responses to salt loading. Accordingly, the present results raise concerns about the interpretation of studies of salt sensitivity with the various Guyton models. These findings indicate a need for continuing development of alternative models that incorporate mechanistic concepts of blood pressure regulation fundamentally different from those in the 1972 Guyton model and its contemporary derivatives.

• MeSH
• hemodynamika fyziologie   MeSH
• hypertenze etiologie   patofyziologie   MeSH
• krevní tlak fyziologie   MeSH
• kuchyňská sůl * MeSH
• lidé MeSH
• minutový srdeční výdej fyziologie   MeSH
• modely kardiovaskulární * MeSH
• počítačová simulace * MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH

Substantial increases in cardiac output (CO), stroke volume (SV), and gastrointestinal blood flow are essential for euryhaline rainbow trout (Oncorhyncus mykiss) osmoregulation in seawater. However, the underlying hemodynamic mechanisms responsible for these changes are unknown. By examining a range of circulatory and cardiac morphological variables of seawater- and freshwater-acclimated rainbow trout, the present study revealed a significantly higher central venous pressure (CVP) in seawater-acclimated trout (~0.09 vs. -0.02 kPa). This serves to increase cardiac end-diastolic volume in seawater and explains the elevations in SV (~0.41 vs. 0.27 ml/kg) and CO (~21.5 vs. 14.2 ml·min(-1)·kg(-1)) when compared with trout in freshwater. Furthermore, these hemodynamic modifications coincided with a significant increase in the proportion of compact myocardium, which may be necessary to compensate for the increased wall tension associated with a larger stroke volume. Following a temperature increase from 10 to 16.5°C, both acclimation groups exhibited similar increases in heart rate (Q10 of ~2), but SV tended to decrease in seawater-acclimated trout despite the fact that CVP was maintained in both groups. This resulted in CO of seawater- and freshwater-acclimated trout stabilizing at a similar level after warming (~26 ml·min(-1)·kg(-1)). The consistently higher CVP of seawater-acclimated trout suggests that factors other than compromised cardiac filling constrained the SV and CO of these individuals at high temperatures. The present study highlights, for the first time, the complex interacting effects of temperature and water salinity on cardiovascular responses in a euryhaline fish species.

• MeSH
• centrální žilní tlak fyziologie   MeSH
• minutový srdeční výdej fyziologie   MeSH
• mořská voda * MeSH
• Oncorhynchus mykiss fyziologie   MeSH
• osmoregulace fyziologie   MeSH
• remodelace komor fyziologie   MeSH
• tepový objem fyziologie   MeSH
• tolerance k soli fyziologie   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

In previous studies, one of the systolic time intervals - preejection period (PEP) - was used as an index of sympathetic activity reflecting the cardiac contractility. However, PEP could be also influenced by several other cardiovascular variables including preload, afterload and diastolic blood pressure (DBP). The aim of this study was to assess the behavior of the PEP together with other potentially confounding cardiovascular system characteristics in healthy humans during mental and orthostatic stress (head-up tilt test - HUT). Forty-nine healthy volunteers (28 females, 21 males, mean age 18.6 years (SD=1.8 years)) participated in the study. We recorded finger arterial blood pressure by volume-clamp method (Finometer Pro, FMS, Netherlands), PEP, thoracic fluid content (TFC) - a measure of preload, and cardiac output (CO) by impedance cardiography (CardioScreen® 2000, Medis, Germany). Systemic vascular resistance (SVR) - a measure of afterload - was calculated as a ratio of mean arterial pressure and CO. We observed that during HUT, an expected decrease in TFC was accompanied by an increase of PEP, an increase of SVR and no significant change in DBP. During mental stress, we observed a decrease of PEP and an increase of TFC, SVR and DBP. Correlating a change in assessed measures (delta values) between mental stress and previous supine rest, we found that deltaPEP correlated negatively with deltaCO and positively with deltaSVR. In orthostasis, no significant correlation between deltaPEP and deltaDBP, deltaTFC, deltaCO, deltaMBP or deltaSVR was found. We conclude that despite an expected increase of sympathetic activity during both challenges, PEP behaved differently indicating an effect of other confounding factors. To interpret PEP values properly, we recommend simultaneously to measure other variables influencing this cardiovascular measure.

• MeSH
• krevní tlak fyziologie   MeSH
• lidé MeSH
• minutový srdeční výdej fyziologie   MeSH
• mladiství MeSH
• mladý dospělý MeSH
• psychický stres patofyziologie   psychologie   MeSH
• srdeční frekvence fyziologie   MeSH
• sympatický nervový systém fyziologie   MeSH
• tepový objem fyziologie   MeSH
• test na nakloněné rovině metody   MeSH
• Check Tag
• lidé MeSH
• mladiství MeSH
• mladý dospělý MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH

Aims: Short-term studies have reported left ventricular (LV) dilatation following surgical creation of arteriovenous fistulas (AVF) or arteriovenous grafts (AVGs), but chronic cardiac structural and functional changes have not been examined or related to clinical outcomes following AVF/AVG. We sought to characterize the long-term changes in cardiac structure and function in patients undergoing shunt creation for haemodialysis. Methods and results: A retrospective analysis was performed of patients undergoing echocardiography before and after surgical AVF/AVG creation for the initiation of haemodialysis. 137 patients underwent echocardiographic examinations prior to AVF and 2.6 years (median) after AVF creation. Following AVF and dialysis initiation, there were reductions in blood pressure, body weight and estimated plasma volume coupled with modest reverse LV remodelling. In contrast, AVF/AVG creation was associated with significant right ventricular (RV) dilatation and deterioration in RV function. Incident heart failure (HF) developed in 43% of patients in tandem with greater RV remodeling. The development of RV dilation following surgical AVF/AVG was independently associated with increased risk of death [HR 3.9, 95% CI (1.7-9.2), P = 0.001]. Conclusion: In long-term follow-up, RV remodelling and dysfunction develop following AVF/AVG creation and dialysis initiation, despite improved control of LV pressure load through dialysis. Deleterious effects on right heart structure and function are coupled with development of incident HF and increased risk of death. Further study is required to identify patients at greatest risk for detrimental AVF/AVG changes who may benefit from alternate forms of dialysis or potentially ligation of existing AVF.

• MeSH
• arteriovenózní zkrat škodlivé účinky   MeSH
• chronické selhání ledvin patofyziologie   terapie   MeSH
• dialýza ledvin MeSH
• echokardiografie MeSH
• funkce pravé komory srdeční fyziologie   MeSH
• kardiorenální syndrom etiologie   patofyziologie   MeSH
• krevní tlak fyziologie   MeSH
• lidé MeSH
• minutový srdeční výdej fyziologie   MeSH
• objem plazmy fyziologie   MeSH
• pooperační komplikace etiologie   patofyziologie   MeSH
• remodelace komor fyziologie   MeSH
• retrospektivní studie MeSH
• senioři MeSH
• tělesná hmotnost fyziologie   MeSH
• výsledek terapie MeSH
• Check Tag
• lidé MeSH
• mužské pohlaví MeSH
• senioři MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH

Hodnocení srdeční funkce je klíčový prvek pro odhad prognózy srdečních onemocnění. Posouzení srdeční funkce in vivo je však ovlivněno mnoha faktory, univerzální parametr, který by definoval status „mechanicky zdravého srdce“, proto neexistuje. V přehledu jsou nové i stávající ukazatele srdeční funkce rozděleny podle toho, zda vyjadřují kontraktilitu nebo mechanickou energii srdeční činnosti. Je diskutována jejich role v hodnocení srdeční fyziologie, způsoby stanovení, možné klinické využití i nevýhody.

Heart function evaluation is a key element in predicting heart disease prognosis. However, in vivo cardiac function assessment is influenced by many factors, and therefore there is no universal parameter defining the status of a "mechanically healthy heart". In this review, new and existing parameters of heart function are divided according to whether they express contractility or mechanical energy of cardiac function. Their role in the evaluation of cardiac physiology, methods of assessment, possible clinical use and disadvantages are discussed.

• Klíčová slova
• systolická elastance, srdeční kontraktilita, endsystolická elastance, preload recruitable stroke work, srdeční výkon, ejekční frakce,
• MeSH
• funkční vyšetření srdce metody   MeSH
• infarkt myokardu diagnóza   MeSH
• kontrakce myokardu * fyziologie   MeSH
• lidé MeSH
• minutový srdeční výdej fyziologie   MeSH
• srdce - funkce komor * fyziologie   MeSH
• srdeční frekvence fyziologie   MeSH
• systola fyziologie   MeSH
• tepový objem * MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• přehledy MeSH