Insights into RC time curve fit analysis of pulmonary artery pressure decay.

The notion of a constant relationship between resistance and capacitance (RC time) in the pulmonary circulation has been challenged by more recent research. The RC time can be obtained using either a simplified empirical approach or a semilogarithmic equation. Although direct curve-fit analysis is a feasible and ostensibly reference approach for RC analysis, it remains largely unexplored. We aimed to study the relationship between various RC methods in different states of pulmonary hemodynamics. Methods In total, 182 patients underwent clinically indicated right heart catheterization. The pressure curves were exported and processed using the MATLAB software. We calculated the RC time using the empirical method (RCEST), semilogarithmic approach (RCSL), and direct measurement of curve fit (RCFIT). Results Among 182 patients, 137 had pulmonary hypertension due to left heart disease (PH-LHD), 35 had pulmonary arterial hypertension (PAH), and 10 demonstrated normal hemodynamics (non-PH). RCEST consistently overestimated the RCFIT and RCSL measurements by a mean of 75%. With all three methods, the RC values were longer in the PAH (RCFIT = 0.36 ± 0.14 s) than in the PH-LHD (0.27 ± 0.1 s) and non-PH (0.27 ± 0.09 s) groups (p < 0.001). Although the RCSL and RCFIT values were similar among the three subgroups, they exhibited broad limits of agreement. Finally, the RCEST demonstrated a strong discriminatory ability (AUC = 0.86, p < 0.001, CI = 0.79-0.93) in identifying PAH. Conclusion RC time in PAH patients was substantially prolonged compared to that in PH-LHD and non-PH patients. The use of the empirical formula yielded systematic RC overestimation. In contrast, the semilogarithmic analysis provided reliable RC estimates, particularly for group comparisons.

What determines systemic blood flow in vertebrates?

In the 1950s, Arthur C. Guyton removed the heart from its pedestal in cardiovascular physiology by arguing that cardiac output is primarily regulated by the peripheral vasculature. This is counterintuitive, as modulating heart rate would appear to be the most obvious means of regulating cardiac output. In this Review, we visit recent and classic advances in comparative physiology in light of this concept. Although most vertebrates increase heart rate when oxygen demands rise (e.g. during activity or warming), experimental evidence suggests that this tachycardia is neither necessary nor sufficient to drive a change in cardiac output (i.e. systemic blood flow, Q̇sys) under most circumstances. Instead, Q̇sys is determined by the interplay between vascular conductance (resistance) and capacitance (which is mainly determined by the venous circulation), with a limited and variable contribution from heart function (myocardial inotropy). This pattern prevails across vertebrates; however, we also highlight the unique adaptations that have evolved in certain vertebrate groups to regulate venous return during diving bradycardia (i.e. inferior caval sphincters in diving mammals and atrial smooth muscle in turtles). Going forward, future investigation of cardiovascular responses to altered metabolic rate should pay equal consideration to the factors influencing venous return and cardiac filling as to the factors dictating cardiac function and heart rate.

Prognostic Value of Preoperative Pulmonary Arterial Capacitance for Patients Undergoing Aortic Valve Replacement for Severe Aortic Valve Stenosis.

BACKGROUND: Pulmonary arterial capacitance (PAC) is a determinant of right ventricular afterload and a strong independent predictor of unfavorable outcomes in advanced heart failure (HF) with pulmonary hypertension (PH). We aimed to test the hypothesis that preoperative PAC may affect postoperative clinical outcomes in patients undergoing aortic valve replacement (AVR) for severe aortic valve stenosis (AS), even in the absence of PH.Methods and Results:We studied 116 patients who underwent AVR for severe AS between January 2005 and December 2017. Right heart catheterization was performed for all patients prior to surgery. PAC and pulmonary vascular resistance (PVR) fit well to a hyperbolic relationship (PAC=0.23/PVR, R2=0.73). PAC also showed an inverse relationship with pulmonary capillary wedge pressure (PCWP) (r=-0.15) and mean pulmonary arterial pressure (r=-0.29) and provided a stronger prediction of death or HF admission than PCWP or PVR (area under the ROC curve of 0.74 vs. 0.40 and 0.41, respectively, P=0.002). During a median follow-up of 36 months, PAC (hazard ratio, 0.48; 95% confidence interval, 0.30-0.78; P=0.003) was an independent predictor of death or hospitalization for HF. CONCLUSIONS: In these patients undergoing AVR for severe AS, even in the absence of PH, preoperative reduced PAC was independently associated with adverse surgical outcomes. It seems that preoperative PAC has potential as an independent predictor of long-term prognosis after AVR for severe AS.

Pulmonary arterial compliance is a useful predictor of pulmonary vascular disease in congenital heart disease.

Histopathological assessment of the pulmonary arteries is crucial to determine the surgical indications in patients with congenital heart disease (CHD) and intractable pulmonary vascular disease (PVD). We aimed to clarify whether pulmonary hemodynamic parameters can predict PVD in patients with CHD and pulmonary arterial hypertension (PAH) We performed histopathological evaluations of lung specimens and cardiac catheterizations in 27 patients with CHD-PAH. We divided these patients into the patients with and without PVD, and compared pulmonary hemodynamic parameters including pulmonary arterial compliance (Cp) between two groups. Age at lung biopsy was 4 (2-7) months. There were 16 patients with trisomy 21. Cardiac diagnosis included ventricular septal defect in 16, atrial septal defect in 5, atrioventricular septal defect in 4, and others in 2. There were 11 patients with histopathologically proven PVD (Heath-Edwards classification grade ≥ 3 in 5; the index of PVD ≥ 1.1 in 3; extremely thickened media in 6; hypoplasia of the pulmonary arteries in 3). Cp in the patients with PVD was significantly lower than that in patients without PVD (0.99 [0.74-1.42] vs 1.56 [1.45-1.88], p = 0.0047), although there was no significant difference in the ratio of systemic to pulmonary blood flow, pulmonary arterial pressure, and resistance between two groups. A Cp cutoff value of < 1.22 ml/mmHg m2 as a predictor of PVD yielded a sensitivity and a specificity of 93% and 64%, respectively. Pulmonary arterial compliance can be a predictor of PVD among patients with CHD-PAH.

Acute stimulation of the soluble guanylate cyclase does not impact on left ventricular capacitance in normal and hypertrophied porcine hearts in vivo.

Experimental data indicate that stimulation of the nitric oxide-soluble guanylate cyclase(sGC)-cGMP-PKG pathway can increase left ventricular (LV) capacitance via phosphorylation of the myofilamental protein titin. We aimed to test whether acute pharmacological sGC stimulation with BAY 41-8543 would increase LV capacitance via titin phosphorylation in healthy and deoxycorticosteroneacetate (DOCA)-induced hypertensive pigs. Nine healthy Landrace pigs and 7 pigs with DOCA-induced hypertension and LV concentric hypertrophy were acutely instrumented to measure LV end-diastolic pressure-volume relationships (EDPVRs) at baseline and during intravenous infusion of BAY 41-8543 (1 and 3 µg·kg-1·min-1 for 30 min, respectively). Separately, in seven healthy and six DOCA pigs, transmural LV biopsies were harvested from the beating heart to measure titin phosphorylation during BAY 41-8543 infusion. LV EDPVRs before and during BAY 41-8543 infusion were superimposable in both healthy and DOCA-treated pigs, whereas mean aortic pressure decreased by 20-30 mmHg in both groups. Myocardial titin phosphorylation was unchanged in healthy pigs, but total and site-specific (Pro-Glu-Val-Lys and N2-Bus domains) titin phosphorylation was increased in DOCA-treated pigs. Bicoronary nitroglycerin infusion in healthy pigs ( n = 5) induced a rightward shift of the LV EDPVR, demonstrating the responsiveness of the pathway in this model. Acute systemic sGC stimulation with the sGC stimulator BAY 41-8543 did not recruit an LV preload reserve in both healthy and hypertrophied LV porcine myocardium, although it increased titin phosphorylation in the latter group. Thus, increased titin phosphorylation is not indicative of increased in vivo LV capacitance. NEW & NOTEWORTHY We demonstrate that acute pharmacological stimulation of soluble guanylate cyclase does not increase left ventricular compliance in normal and hypertrophied porcine hearts. Effects of long-term soluble guanylate cyclase stimulation with oral compounds in disease conditions associated with lowered myocardial cGMP levels, i.e., heart failure with preserved ejection fraction, remain to be investigated.

Ethnic differences in stratum corneum functions between Chinese and Thai infants residing in Bangkok, Thailand.

BACKGROUND/OBJECTIVES: Ethnic and racial differences in infant skin have not been well characterized. The purpose of this study was to establish whether there are ethnic differences and similarities in the stratum corneum (SC) functions of Thai and Chinese infants. METHODS: Healthy infants 6 to 24 months of age (N = 60; 30 Thai, 30 Chinese) who resided in Bangkok, Thailand, were enrolled. Transepidermal water loss (TEWL) and SC hydration (capacitance) on the thigh, buttock, and upper arm were measured. Ceramide content was determined in the SC on the upper arm. RESULTS: SC hydration was not remarkably different between the two ethnicities at any site measured, but TEWL was significantly higher in Chinese infants than in Thai infants at all sites. Hydration of the SC was not significantly correlated with age in either ethnicity. TEWL had significant but weak correlations with age on the thigh and upper arm in Thai infants. Ceramide content was significantly higher in Chinese SC than in Thai SC. No relationship between ceramide content and TEWL or hydration was observed in either ethnicity. CONCLUSION: The significant differences in TEWL and ceramide contents between Chinese and Thai infant skin could prove useful in designing skin care and diapering products that are best suited for each ethnicity.

Altered cardiovascular function is related to reduced BDNF in Parkinson's disease.

Brain-derived neurotrophic factor (BDNF) has been linked to cardiovascular health and function, however, the exact role is yet to be understood. The current study examined the relationship of circulatory BDNF with vascular function in Parkinson's disease (PD). ELISA was used to determine plasma BDNF in PD patients and healthy control (CT). Additionally, forearm resting blood flow (RBf), vascular resistance (RVr), venous capacitance (RVc), and venous outflow (RVo) as well as post occlusion blood flow (OcBf), vascular resistance (OcVr), venous capacitance (OcVc), and venous outflow (OcVo) were obtained using strain-gauge plethysmography. Simple linear regression showed that being PD patient can predict (p < 0.05) 12.9% of BDNF, 16.8% of RVc, 15.0% of OcVc, and 13.6% of OcVo. Subsequent stepwise regression included BDNF, RVc, OcVc, and OcVo, showed that being PD patient predicted (p < 0.05) 58.0% of BDNF, 47.7% of OcVo, and 15.1% of OcVc. Another simple linear regression demonstrated that BDNF predicted (p < 0.05) 18.5% of OcBf, 22.0% of OcVr, and 24.1% of OcVc in PD. In a subsequent stepwise linear regression, BDNF explained 26% ofOcVr (p = 0.008) and 42% of OcVc (p = 0.002) in PD. The study showed that BDNF is reduced and related to altered vascular function in PD. The results suggest that BDNF might contribute to preserving and maybe improving vascular function in PD.

Pulmonary Arterial Capacitance Index Is a Strong Predictor for Adverse Outcome in Children with Idiopathic and Heritable Pulmonary Arterial Hypertension.

OBJECTIVES: To evaluate the clinical utility of pulmonary artery capacitance index (PACi) in the assessment of disease severity and prognostic value in children with idiopathic and heritable pulmonary arterial hypertension (PAH). STUDY DESIGN: PACi is defined as the ratio of stroke volume index over pulmonary pulse pressure. A retrospective study was performed to compare PACi, brain natriuretic peptide (BNP), 6-minute walk distance, New York Heart association (NYHA) functional class, and adverse outcomes (hospitalization due to heart failure, lung transplantation, and cardiac mortality) in 72 Japanese children (10 ± 3.6 years) with idiopathic and heritable PAH. RESULTS: PACi had significant correlations with pulmonary vascular resistance index (r =-0.73, P < .0001), BNP levels (r = -0.40, P = .0008), and 6-minute walk distance (r = 0.57, P < .05). Statistically significant differences in PACi were observed between NYHA functional class II vs combined III and IV (median; 1.1 vs 0.6 mL/mm Hg/m2, respectively, P < .05). There were 25 of 72 (35%) children who had an adverse event including initiation of hospitalization due to heart failure, lung transplantation, and death. Cumulative event-free survival rate was significantly lower when PACi was <0.85 mL/mm Hg/m2 (log-rank test, P < .0001). CONCLUSIONS: PACi correlated with BNP and NYHA functional class and may serve as a strong prognostic marker in children with idiopathic and heritable PAH.

Assessing intracranial vascular compliance using dynamic arterial spin labeling.

Vascular compliance (VC) is an important marker for a number of cardiovascular diseases and dementia, which is typically assessed in the central and peripheral arteries indirectly by quantifying pulse wave velocity (PWV), and/or pulse pressure waveform. To date, very few methods are available for the quantification of intracranial VC. In the present study, a novel MRI technique for in-vivo assessment of intracranial VC was introduced, where dynamic arterial spin labeling (ASL) scans were synchronized with the systolic and diastolic phases of the cardiac cycle. VC is defined as the ratio of change in arterial cerebral blood volume (ΔCBV) and change in arterial pressure (ΔBP). Intracranial VC was assessed in different vascular components using the proposed dynamic ASL method. Our results show that VC mainly occurs in large arteries, and gradually decreases in small arteries and arterioles. The comparison of intracranial VC between young and elderly subjects shows that aging is accompanied by a reduction of intracranial VC, in good agreement with the literature. Furthermore, a positive association between intracranial VC and cerebral perfusion measured using pseudo-continuous ASL with 3D GRASE MRI was observed independent of aging effects, suggesting loss of VC is associated with a decline in perfusion. Finally, a significant positive correlation between intracranial and central (aortic arch) VC was observed using an ungated phase-contrast 1D projection PWV technique. The proposed dynamic ASL method offers a promising approach for assessing intracranial VC in a range of cardiovascular diseases and dementia.

The effect of propofol on haemodynamics: cardiac output, venous return, mean systemic filling pressure, and vascular resistances.

BACKGROUND: Although arterial hypotension occurs frequently with propofol use in humans, its effects on intravascular volume and vascular capacitance are uncertain. We hypothesized that propofol decreases vascular capacitance and therefore decreases stressed volume. METHODS: Cardiac output (CO) was measured using Modelflow(®) in 17 adult subjects after upper abdominal surgery. Mean systemic filling pressure (MSFP) and vascular resistances were calculated using venous return curves constructed by measuring steady-state arterial and venous pressures and CO during inspiratory hold manoeuvres at increasing plateau pressures. Measurements were performed at three incremental levels of targeted blood propofol concentrations. RESULTS: Mean blood propofol concentrations for the three targeted levels were 3.0, 4.5, and 6.5 µg ml(-1). Mean arterial pressure, central venous pressure, MSFP, venous return pressure, Rv, systemic arterial resistance, and resistance of the systemic circulation decreased, stroke volume variation increased, and CO was not significantly different as propofol concentration increased. CONCLUSIONS: An increase in propofol concentration within the therapeutic range causes a decrease in vascular stressed volume without a change in CO. The absence of an effect of propofol on CO can be explained by the balance between the decrease in effective, or stressed, volume (as determined by MSFP), the decrease in resistance for venous return, and slightly improved heart function. CLINICAL TRIAL REGISTRATION: Netherlands Trial Register: NTR2486.

Pulmonary Vascular Capacitance is Associated with Vasoreactivity and Long-Term Response to Calcium Channel Blockers in Idiopathic Pulmonary Arterial Hypertension.

PURPOSE: This study aimed to identify the relationship between pulmonary vascular capacitance (PVC) and vasoreactivity in patients with idiopathic pulmonary arterial hypertension (IPAH), and the value of PVC in predicting long-term response to CCB treatment. METHODS: Pulmonary vasodilator testing with inhaling iloprost was performed in 308 newly diagnosed IPAH patients. Acute vasodilator-responsive patients accepted CCBs treatment. Patients who benefit from long-term CCB were defined as those being in World Health Organization (WHO) functional class II or I after at least 1 year on CCB monotherapy. RESULTS: PVC had significant correlations with WHO function class, 6-min walk distance, mean pulmonary arterial pressure, and pulmonary vascular resistance (r = -0.363, p < 0.001; r = 0.333, p < 0.001; r = -0.514, p < 0.001; r = -0.739, p < 0.001). Thirty-five acute vasodilator-responsive IPAH patients (11.4 %) displayed less severe disease and a higher baseline PVC (1.5 ± 0.6 vs. 1.1 ± 0.7 ml/mmHg, p = 0.003). During acute vasodilator testing, PVC increased significantly by mean of 79 ± 48 % and reached to a higher absolute value of 2.6 ± 1.5 ml/mmHg compared with non-responsive patients (1.4 ± 1.5 ml/mmHg, p < 0.001). Furthermore, PVC increased more during acute vasodilator testing in the 24 patients who benefit from long-term CCB treatment (1.4 ± 1.3 vs. 0.5 ± 0.4 ml/mmHg, p = 0.004). The OR of increased PVC during vasodilator testing for predicting patients with long-term response to CCB was 1.24 (95 % CI 1.02-1.50, p = 0.031) as assessed by multivariable logistic regression analysis. CONCLUSIONS: PVC was higher in acute vasodilator-responsive IPAH patients and may be a predictor of long-term response to CCBs therapy.

The BAR domain protein PICK1 controls vesicle number and size in adrenal chromaffin cells.

Protein Interacting with C Kinase 1 (PICK1) is a Bin/Amphiphysin/Rvs (BAR) domain protein involved in AMPA receptor trafficking. Here, we identify a selective role for PICK1 in the biogenesis of large, dense core vesicles (LDCVs) in mouse chromaffin cells. PICK1 colocalized with syntaxin-6, a marker for immature granules. In chromaffin cells isolated from a PICK1 knockout (KO) mouse the amount of exocytosis was reduced, while release kinetics and Ca(2+) sensitivity were unaffected. Vesicle-fusion events had a reduced frequency and released lower amounts of transmitter per vesicle (i.e., reduced quantal size). This was paralleled by a reduction in the mean single-vesicle capacitance, estimated by averaging time-locked capacitance traces. EM confirmed that LDCVs were fewer and of markedly reduced size in the PICK1 KO, demonstrating that all phenotypes can be explained by reductions in vesicle number and size, whereas the fusion competence of generated vesicles was unaffected by the absence of PICK1. Viral rescue experiments demonstrated that long-term re-expression of PICK1 is necessary to restore normal vesicular content and secretion, while short-term overexpression is ineffective, consistent with an upstream role for PICK1. Disrupting lipid binding of the BAR domain (2K-E mutation) or of the PDZ domain (CC-GG mutation) was sufficient to reproduce the secretion phenotype of the null mutant. The same mutations are known to eliminate PICK1 function in receptor trafficking, indicating that the multiple functions of PICK1 involve a conserved mechanism. Summarized, our findings demonstrate that PICK1 functions in vesicle biogenesis and is necessary to maintain normal vesicle numbers and size.

Abdominal Aortic Hemodynamics in Intermittent Claudication Patients at Rest and during Dynamic Pedaling Exercise.

BACKGROUND: Lower-extremity exercise has been shown to eliminate adverse hemodynamics conditions, such as low and oscillating blood flow and wall shear stress, in the abdominal aortas of healthy young and older adults. METHODS: We use cine phase-contrast magnetic resonance imaging and a custom MRI-compatible exercise cycle to quantify hemodynamic changes because of pedaling exercise in patients diagnosed with intermittent claudication. RESULTS: With only an average heart increase of 35 ± 18% and exercise workload of 36 ± 16 watts, the patients experienced approximately 3- and 6-fold increases in blood flow, and 4- and 16-fold increases in wall shear stress at the supraceliac and infrarenal aortic locations, respectively. Also, all oscillations in flow and shear stress at rest were eliminated with exercise. CONCLUSIONS: Claudication patients experience 3- to 4-fold lower oscillations in flow and shear stress at rest as compared with healthy age-matched controls, likely because of reduced distal arterial compliance as a result of distal atherosclerosis. The magnitude of flow and shear oscillatory indices may be good indicators of distal arterial compliance and health, and may provide predictive power for the efficacy of focal interventions.

Systemic vascular effects of acute electrical baroreflex stimulation.

We intended to determine if acute baroreflex activation therapy (BAT) increases venous capacitance and aortic conductance. BAT is effective in resistant hypertension, but its effect on the systemic vasculature is poorly understood. Left ventricular (LV) and aortic pressures and subdiaphragmatic aortic and caval flows (ultrasonic) were measured in six anesthetized dogs. Changes in abdominal blood volume (Vabdominal) were estimated as the integrated difference in abdominal aortic inflow and caval outflow. An electrode was implanted on the right carotid sinus. Data were measured during control and BAT. Next, sodium nitroprusside (SNP) was infused and BAT was subsequently added. Finally, angiotensin II (ANG II) was infused, and three increased BAT currents were added. We found that BAT decreased mean aortic pressure (PAo) by 22.5 ± 1.3 mmHg (P < 0.001) and increased aortic conductance by 16.2 ± 4.9% (P < 0.01) and Vabdominal at a rate of 2.2 ± 0.6 ml·kg(-1)·min(-1) (P < 0.01). SNP decreased PAo by 17.4 ± 0.7 mmHg (P < 0.001) and increased Vabdominal at a rate of 2.2 ± 0.7 ml·kg(-1)·min(-1) (P < 0.05). During the SNP infusion, BAT decreased PAo further, by 26.0 ± 2.1 mmHg (P < 0.001). ANG II increased PAo by 40.4 ± 3.5 mmHg (P = 0.001). When an increased BAT current was added, PAo decreased to baseline (P < 0.01) while aortic conductance increased from 62.3 ± 5.2% to 80.2 ± 3.3% (P < 0.05) of control. Vabdominal increased at a rate of 1.8 ± 0.9 ml·kg(-1)·min(-1) (P < 0.01), reversing the ANG II effects. In conclusion, BAT increases arterial conductance, decreases PAo, and increases venous capacitance even in the presence of powerful vasoactive drugs. Increasing venous capacitance may be an important effect of BAT in hypertension.

Exercise ventilatory parameters for the diagnosis of reactive pulmonary hypertension in patients with heart failure.

BACKGROUND: Reactive pulmonary hypertension (PH) in left heart disease is associated with poor prognosis. This study aimed to evaluate the diagnostic utility of exercise ventilatory parameters on cardiopulmonary exercise testing for the diagnosis of reactive PH in patients with heart failure (HF) and reduced ejection fraction. METHODS: This was a single-center, retrospective analysis of a prospectively collected database of 131 patients with HF who underwent in-hospital assessment for heart transplantation. Pulmonary hemodynamics was assessed by direct cardiac catheterization. Minute ventilation/carbon dioxide production (VE/VCO2) slope, partial pressure of end-tidal carbon dioxide (ETCO2) changes on exercise, oxygen pulse, and exercise oscillatory ventilation were determined from cardiopulmonary exercise testing. RESULTS: Sixty-one of 131 consecutive patients had reactive PH. VE/VCO2 slope (>41), change in ETCO2 on exercise (<1.2 mm Hg) and exercise oscillatory ventilation were independently associated with reactive PH. These 3 parameters in combination produced 3 possible diagnostic scenarios: (1) if all 3 criteria ("if all") were present, (2) if any 2 of the 3 criteria ("2 of 3") were present, and (3) if any of the criteria ("if any") were present. The corresponding positive/negative likelihood ratios for reactive PH if all 3 criteria were present were 3.73/0.83, if 2 of the 3 criteria were present were 2.19/0.45, and if any of the 3 criteria were present were 1.75/0.11. The posttest probability increased from 46% to 76% ("if all" present) and reduced to 9% (if none of the criteria was present). CONCLUSION: Ventilatory parameters on cardiopulmonary exercise test are associated with reactive PH in patients with HF. The absence of abnormalities in these 3 ventilatory parameters can effectively exclude reactive PH in patients with HF and poor ejection fraction.

Chemohypersensitivity and autonomic modulation of venous capacitance in the pathophysiology of acute decompensated heart failure.

Heart failure is increasing in prevalence around the world, with hospitalization and re-hospitalization as a result of acute decompensated heart failure (ADHF) presenting a huge social and economic burden. The mechanism for this decompensation is not clear. Whilst in some cases it is due to volume expansion, over half of patients with an acute admission for ADHF did not experience an increase in total body weight. This calls into question the current treatment strategy of targeting salt and water retention in ADHF. An alternative hypothesis proposed by Fallick et al. is that an endogenous fluid shift from the splanchnic bed is implicated in ADHF, rather than an exogenous fluid gain. The hypothesis states further that this shift is triggered by an increase in sympathetic tone causing vasoconstriction in the splanchnic bed, a mechanism that can translocate blood rapidly into the effective circulating volume, generating the raised venous pressure and congestion seen in ADHF. This hypothesis encourages a new clinical paradigm which focuses on the underlying mechanisms of congestion, and highlights the importance of fluid redistribution and neurohormonal activation in its pathophysiology. In this article, we consider the concept that ADHF is attributable to episodic sympathetic hyperactivity, resulting in fluid shifts from the splanchnic bed. Chemosensitivity is a pathologic autonomic mechanism associated with mortality in patients with systolic heart failure. Tonic and episodic activity of the peripheral chemoreceptors may underlie the syndrome of acute decompensation without total body salt and water expansion. We suggest in this manuscript that chemosensitivity in response to intermittent hypoxia, such as experienced in sleep disordered breathing, may explain the intermittent sympathetic hyperactivity underlying renal sodium retention and acute volume redistribution from venous storage sites. This hypothesis provides an alternative structure to guide novel diagnostic and treatment strategies for ADHF.

[Value of dynamic arterial elastance in the predication of arterial pressure response to volume loading in shock patients].

OBJECTIVE: To explore the value of dynamic arterial elastance (Eadyn) in the predication of arterial pressure response to volume loading in shock patients. METHODS: A total of 32 patients with pulse indicator continuous cardiac output (PICCO) monitoring at our intensive care unit from January 2011 to December 2012 were retrospectively studied. The decision of fluid replacement was based upon the presence of shock (mean arterial pressure (MAP) ≤ 65 mm Hg, systolic arterial pressure <90 mm Hg or a decrease of 40 mm Hg from baseline) and preserved volume responsiveness condition with a stroke volume variation (SVV) value ≥ 10%. According to the MAP increase after volume loading, they were classified into MAP responders (≥ 15%) and MAP nonresponders (<15%) respectively. The goal was to investigate the influencing factors of the changes of MAP after volume loading and predict the arterial pressure response to volume loading. RESULTS: Significantly different between MAP responders and MAP nonresponders, baseline Eadyn was an effective predictor of MAP increase after volume loading. The area under the ROC curve was 0.95 for the prediction of volume loading on MAP for Eadyn at baseline (P < 0.01). A baseline Eadyn value >0.85 predicted a MAP increase after volume administration with a sensitivity of 89.5% and a specificity of 92.3%. CONCLUSION: Baseline Eadyn may predict accurately arterial pressure response in MAP to volume loading in shock patients.

Adrenomedullin-epinephrine cotreatment enhances cardiac output and left ventricular function by energetically neutral mechanisms.

Adrenomedullin (AM) used therapeutically reduces mortality in the acute phase of experimental myocardial infarction. However, AM is potentially deleterious in acute heart failure as it is vasodilative and inotropically neutral. AM and epinephrine (EPI) are cosecreted from chromaffin cells, indicating a physiological interaction. We assessed the hemodynamic and energetic profile of AM-EPI cotreatment, exploring whether drug interaction improves cardiac function. Left ventricular (LV) mechanoenergetics were evaluated in 14 open-chest pigs using pressure-volume analysis and the pressure-volume area-myocardial O(2) consumption (PVA-MVo(2)) framework. AM (15 ng·kg(-1)·min(-1), n = 8) or saline (controls, n = 6) was infused for 120 min. Subsequently, a concurrent infusion of EPI (50 ng·kg(-1)·min(-1)) was added in both groups (AM-EPI vs. EPI). AM increased cardiac output (CO) and coronary blood flow by 20 ± 10% and 39 ± 14% (means ± SD, P < 0.05 vs. baseline), whereas controls were unaffected. AM-EPI increased CO and coronary blood flow by 55 ± 17% and 75 ± 16% (P < 0.05, AM-EPI interaction) compared with 13 ± 12% (P < 0.05 vs. baseline) and 18 ± 31% (P = not significant) with EPI. LV systolic capacitance decreased by -37 ± 22% and peak positive derivative of LV pressure (dP/dt(max)) increased by 32 ± 7% with AM-EPI (P < 0.05, AM-EPI interaction), whereas no significant effects were observed with EPI. Mean arterial pressure was maintained by AM-EPI and tended to decrease with EPI (+2 ± 13% vs. -11 ± 10%, P = not significant). PVA-MVo(2) relationships were unaffected by all treatments. In conclusion, AM-EPI cotreatment has an inodilator profile with CO and LV function augmented beyond individual drug effects and is not associated with relative increases in energetic cost. This can possibly take the inodilator treatment strategy beyond hemodynamic goals and exploit the cardioprotective effects of AM in acute heart failure.

The α2 isoform of the Na,K-pump is important for intercellular communication, agonist-induced contraction, and EDHF-like response in rat mesenteric arteries.

The specific role of different isoforms of the Na,K-pump in the vascular wall is still under debate. We have previously suggested that the α(2) isoform of the Na,K-pump (α(2)), Na(+), Ca(2+)-exchange (NCX), and connexin43 form a regulatory microdomain in smooth muscle cells (SMCs), which controls intercellular communication and contractile properties of the vascular wall. We have tested this hypothesis by downregulating α(2) in cultured SMCs and in small arteries with siRNA in vivo. Intercellular communication was assessed by using membrane capacitance measurements. Arteries transfected in vivo were tested for isometric and isobaric force development in vitro; [Ca(2+)](i) was measured simultaneously. Cultured rat SMCs were well-coupled electrically, but 10 µM ouabain uncoupled them. Downregulation of α(2) reduced electrical coupling between SMCs and made them insensitive to ouabain. Downregulation of α(2) in small arteries was accompanied with significant reduction in NCX expression. Acetylcholine-induced relaxation was not different between the groups, but the endothelium-dependent hyperpolarizing factor-like component of the response was significantly diminished in α(2)-downregulated arteries. Micromolar ouabain reduced in a concentration-dependent manner the amplitude of norepinephrine (NE)-induced vasomotion. Sixty percent of the α(2)-downregulated arteries did not have vasomotion, and vasomotion in the remaining 40% was ouabain insensitive. Although ouabain increased the sensitivity to NE in the control arteries, it had no effect on α(2)-downregulated arteries. In the presence of a low NE concentration the α(2)-downregulated arteries had higher [Ca(2+)](i) and tone. However, the NE EC50 was reduced under isometric conditions, and maximal contraction was reduced under isometric and isobaric conditions. The latter was caused by a reduced Ca(2+)-sensitivity. The α(2)-downregulated arteries also had reduced contraction to vasopressin, whereas the contractile response to high K(+) was not affected. Our results demonstrate the importance of α(2) for intercellular coupling in the vascular wall and its involvement in the regulation of vascular tone.