The renin angiotensin aldosterone system

In this review, we will cover (i) the proteolytic cascade of the RAAS, (ii) its regulation by multiple feedback-controlled parameters, and (iii) the major effects of the RAAS. For the effects of the RAAS, we focus on the role of the RAAS in the regulation of volume homeostasis and vascular tone, as major determinants of arterial blood pressure.

Insulin resistance in the adipose tissue predicts future vascular resistance: The Hiroshima Study on Glucose Metabolism and Cardiovascular Diseases

BACKGROUND AND AIMS

Diameter, plaque score, and resistance index (RI) in the common carotid artery (CCA) are indicators of arterial remodeling, atherosclerosis, and vascular resistance, respectively. This study investigated the longitudinal association between adipose tissue insulin resistance or serum free fatty acid (FFA) levels and the CCA parameters.

METHODS

This retrospective cohort analysis included 1089 participants (mean age 57.6 years; 40.0 % women) with data on health checkups from January 1982 to March 2003 and carotid artery ultrasonography from January 2015 to June 2019. Baseline serum FFA and immunoreactive insulin levels were assessed before and 30, 60, and 120 min after glucose ingestion. Adipose insulin resistance index (Adipo-IR) was calculated as the product of fasting serum insulin and FFA levels. An RI value >0.75 was defined as high RI.

RESULTS

A significant association was found between Adipo-IR and RI; however, Adipo-IR showed no association with CCA diameter or plaque score. The incidence of high RI increased with Adipo-IR quartile (Q) groups (47.3 % in Q1, 52.8 % in Q2, 53.3 % in Q3, 62.4 % in Q4; Cochrane-Armitage test for trend, p < 0.001). In multivariate analysis, Adipo-IR levels (Q4 vs. Q1 odds ratio: 1.67, 95 % confidence interval: 1.12-2.51) were positively associated with high RI incidence. Moreover, a significant association was found between RI and serum FFA levels after glucose intake, but not fasting FFA levels.

CONCLUSIONS

Future vascular resistance was predicted by insulin resistance in the adipose tissue. After glucose intake, serum FFA levels may significantly impact vascular resistance development.

Influence of circle of Willis modeling on hemodynamic parameters in anterior communicating artery aneurysms and recommendations for model selection

Computational fluid dynamics (CFD) has been utilized to calculate hemodynamic parameters in anterior communicating artery aneurysm (AComA), which is located at a junction between left and right A1 and A2 segments. However, complete or half circle of Willis (CoW) models are used indiscriminately. This study aims to suggest recommendations for determining suitable CoW model. Five patient-specific CoW models with AComA were used, and each model was divided into complete, left-half, and right-half models. After validating the CFD using a flow experiment, the hemodynamic parameters and flow patterns in five AComAs were compared. In four out of five cases, inflow from one A1 side had a dominant influence on the AComA, while both left and right A1 sides affected the AComA in the remaining case. Also, the average difference in time-averaged wall shear stress between the complete and half models for four cases was 4.6%, but it was 62% in the other case. The differences in the vascular resistances of left and right A1 and A2 segments greatly influenced the flow patterns in the AComA. These results may help to enhance clinicians' understanding of blood flow in the brain, leading to improvements in diagnosis and treatment of cerebral aneurysms.

Naphazoline intoxication managed with minimally invasive cardiac output monitoring

Naphazoline, a nonspecific alpha-adrenoceptor stimulant, is a potent vasoconstrictor used in nasal sprays, eye drops, and over-the-counter antiseptics. Naphazoline intoxication increases afterload by constricting the peripheral arteries, which can lead to complications including multiple organ failure. Although phentolamine, a nonselective alpha-adrenoceptor antagonist, and nicardipine, a calcium channel blocker, are used for the treatment of naphazoline intoxication, no established administration protocols currently exist. We present the case of a 32-year-old male with depression who ingested 150 mL of an antiseptic containing 0.1% naphazoline (equivalent to 150 mg of naphazoline). Five hours after ingestion, the patient was admitted to hospital exhibiting signs of naphazoline intoxication, such as bradycardia (46 beats/min), blood pressure of 166/122 mmHg, and peripheral cyanosis. We used the FloTrac™/EV1000™ system (Edwards Lifesciences, Irvine, CA, USA), a minimally invasive cardiac output monitoring system, to monitor systemic vascular resistance. The systemic vascular resistance index (SVRI) was elevated (4457 dyne.s/cm5/m2; nomal range: 1970-2390 dyne.s/cm5/m2) upon admission and initial treatment with continuous intravenous infusion of phentolamine led to SVRI normalization within 2 h. With the goal of maintaining SVRI normalization, continuous infusion with nicardipine was then started. At 10 h after treatment initiation, the nicardipine dose peaked at 9 mg/h (1.9 μg/kg/min). Treatment was discontinued 8 h later, and the patient was discharged on the fourth day without sequelae. In conclusion, the use of a minimally invasive cardiac output monitoring system to track vascular resistance can effectively guide the dosing of phentolamine or nicardipine in the treatment of naphazoline intoxication.

Osmotic response during kidney perfusion with cryoprotectant in isotonic or hypotonic vehicle solution

Organ cryopreservation would revolutionize transplantation by overcoming the shelf-life limitations of conventional organ storage. To prepare an organ for cryopreservation, it is first perfused with cryoprotectants (CPAs). These chemicals can enable vitrification during cooling, preventing ice damage. However, CPAs can also cause toxicity and osmotic damage. It is a major challenge to find the optimal balance between protecting the cells from ice and avoiding CPA-induced damage. In this study, we examined the organ perfusion process to shed light on phenomena relevant to cryopreservation protocol design, including changes in organ size and vascular resistance. In particular, we compared perfusion of kidneys (porcine and human) with CPA in either hypotonic or isotonic vehicle solution. Our results demonstrate that CPA perfusion causes kidney mass changes consistent with the shrink-swell response observed in cells. This response was observed when the kidneys were relatively fresh, but disappeared after prolonged warm and/or cold ischemia. Perfusion with CPA in a hypotonic vehicle solution led to a significant increase in vascular resistance, suggesting reduced capillary diameter due to cell swelling. This could be reversed by switching to perfusion with CPA in isotonic vehicle solution. Hypotonic vehicle solution did not cause notable osmotic damage, as evidenced by low levels of lactate dehydrogenase (LDH) in the effluent, and it did not have a statistically significant effect on the delivery of CPA into the kidney, as assessed by computed tomography (CT). Overall, our results show that CPA vehicle solution tonicity affects organ size and vascular resistance, which may have important implications for cryopreservation protocol design.

Comparison of invasive and non-invasive measurements of cardiac index and systemic vascular resistance in living-donor liver transplantation: a prospective, observational study

BACKGROUND

Based on the controversy surrounding pulmonary artery catheterization (PAC) in surgical patients, we investigated the interchangeability of cardiac index (CI) and systemic vascular resistance (SVR) measurements between ClearSight™ and PAC during living-donor liver transplantation (LDLT).

METHODS

This prospective study included consecutively selected LDLT patients. ClearSight™-based CI and SVR measurements were compared with those from PAC at seven LDLT-stage time points. ClearSight™-based systolic (SAP), mean (MAP), and diastolic (DAP) arterial pressures were also compared with those from femoral arterial catheterization (FAC). For the comparison and analysis of ClearSight™ and the reference method, Bland-Altman analysis was used to analyze accuracy while polar and four-quadrant plots were used to analyze the trending ability.

RESULTS

From 27 patients, 189 pairs of ClearSight™ and reference values were analyzed. The CI and SVR performance errors (PEs) exhibited poor accuracy between the two methods (51.52 and 51.73%, respectively) in the Bland-Altman analysis. CI and SVR also exhibited unacceptable trending abilities in both the polar and four-quadrant plot analyses. SAP, MAP, and DAP PEs between the two methods displayed favorable accuracy (24.28, 21.18, and 26.26%, respectively). SAP and MAP exhibited acceptable trending ability in the four-quadrant plot between the two methods, but not in the polar plot analyses.

CONCLUSIONS

During LDLT, CI and SVR demonstrated poor interchangeability, while SAP and MAP exhibited acceptable interchangeability between ClearSight™ and FAC.

Impact of Pulmonary Arterial Elastance on Right Ventricular Mechanics and Exercise Capacity in Repaired Tetralogy of Fallot

BACKGROUND AND OBJECTIVES

Pathophysiological changes of right ventricle (RV) after repair of tetralogy of Fallot (TOF) are coupled with a highly compliant low-pressure pulmonary artery (PA) system. This study aimed to determine whether pulmonary vascular function was associated with RV parameters and exercise capacity, and its impact on RV remodeling after pulmonary valve replacement.

METHODS

In a total of 48 patients over 18 years of age with repaired TOF, pulmonary arterial elastance (Ea), RV volume data, and RV-PA coupling ratio were calculated and analyzed in relation to exercise capacity.

RESULTS

Patients with a low Ea showed a more severe pulmonary regurgitation volume index, greater RV end-diastolic volume index, and greater effective RV stroke volume (p=0.039, p=0.013, and p=0.011, respectively). Patients with a high Ea had lower exercise capacity than those with a low Ea (peak oxygen consumption [peak VO₂] rate: 25.8±7.7 vs. 34.3±5.5 mL/kg/min, respectively, p=0.003), while peak VO₂ was inversely correlated with Ea and mean PA pressure (p=0.004 and p=0.004, respectively). In the univariate analysis, a higher preoperative RV end-diastolic volume index and RV end-systolic volume index, left ventricular end-systolic volume index, and higher RV-PA coupling ratio were risk factors for suboptimal outcomes. Preoperative RV volume and RV-PA coupling ratio reflecting the adaptive PA system response are important factors in optimal postoperative results.

CONCLUSIONS

We found that PA vascular dysfunction, presenting as elevated Ea in TOF, may contribute to exercise intolerance. However, Ea was inversely correlated with pulmonary regurgitation (PR) severity, which may prevent PR, RV dilatation, and left ventricular dilatation in the absence of significant pulmonary stenosis.

Hemodynamic profiles of arterial hypertension with ambulatory blood pressure monitoring

Blood pressure (BP) measurements obtained during a twenty-four-hour ambulatory blood pressure monitoring (24 h ABPM) have not been reliably applied to extract arterial hemodynamics. We aimed to describe the hemodynamic profiles of different hypertension (HT) subtypes derived from a new method for total arterial compliance (C_t) estimation in a large group of individuals undergoing 24 h ABPM. A cross-sectional study was conducted, which included patients with suspected HT. Cardiac output, C_t, and total peripheral resistance (TPR) were derived through a two-element Windkessel model without having a pressure waveform. Arterial hemodynamics were analyzed according to HT subtypes in 7434 individuals (5523 untreated HT and 1950 normotensive controls [N]). The individuals mean age was 46.2 ± 13.0 years; 54.8% were male, and 22.1% were obese. In isolated diastolic hypertension (IDH), the cardiac index (CI) was greater than that in normotensive (N) controls (CI: IDH vs. N mean difference 0.10 L/m/m²; CI 95% 0.08 to 0.12; p value <0.001), with no significant clinical difference in C_t. Isolated systolic hypertension (ISH) and divergent systolic-diastolic hypertension (D-SDH) had lower C_t values than nondivergent HT subtype (C_t: divergent vs. nondivergent mean difference -0.20 mL/mmHg; CI 95% -0.21 to -0.19 mL/mmHg; p value <0.001). Additionally, D-SDH displayed the highest TPR (TPR: D-SDH vs. N mean difference 169.8 dyn*s/cm^-5; CI 95% 149.3 to 190.3 dyn*s/cm^-5; p value <0.001). A new method is provided for the simultaneous assessment of arterial hemodynamics with 24 h ABPM as a single diagnostic tool, which allows a comprehensive assessment of arterial function for hypertension subtypes. Main hemodynamic findings in arterial HT subtypes with regard to C_t and TPR. The 24 h ABPM profile reflects the state of C_t and TPR. Younger individuals with IDH present with a normal C_t and frequently increased CO. Patients with ND-SDH maintain an adequate C_t with a higher TPR, while subjects with D-SDH present with a reduced C_t, high PP and high TPR. Finally, the ISH subtype occurs in older individuals with significantly reduced C_t, high PP and a variable TPR proportional to the degree of arterial stiffness and MAP values. There was an observed increase in PP with age in relation to the changes in C_t (see also text). SBP: systolic blood pressure; DBP: diastolic blood pressure; MAP: mean arterial pressure; PP: pulse pressure; N: normotension; HT: hypertension; IDH: isolated diastolic hypertension; ND-SDH: nondivergent systole-diastolic hypertension; D-SDH: divergent systolic-diastolic hypertension; ISH: isolated systolic hypertension; C_t: total arterial compliance; TPR: total peripheral resistance; CO: cardiac output; 24 h ABPM: 24 h ambulatory blood pressure monitoring.

Applicability of the histidine-tryptophan-ketoglutarate solution as a machine perfusion solution for marginal liver grafts

BACKGROUND AND AIM

There are very few reports comparing the use of the University of Wisconsin solution and histidine-tryptophan-ketoglutarate solution as machine perfusion solutions for marginal liver grafts. We aimed to clarify whether the use of the histidine-tryptophan-ketoglutarate solution in hypothermic machine perfusion improves the split-liver graft function in a large animal model.

METHODS

Porcine split-liver grafts were created by 75% liver resection. Hypothermic machine perfusion experimental groups were divided as follows: Group 1, perfusate, University of Wisconsin gluconate solution (UW group; n = 5), and Group 2, perfusate, histidine-tryptophan-ketoglutarate solution (HTK group; n = 4). After 4 h of preservation, the liver function was evaluated using an isolated liver reperfusion model for 2 h.

RESULTS

In the HTK group, the portal vein and hepatic artery resistance during hypothermic machine perfusion and the portal vein resistance during isolated liver reperfusion were lower than those in the UW group. In addition, the total Suzuki score for hepatic ischemia-reperfusion injury in the HTK group was significantly better than that in the UW group. The number of anti-ETS-related genes staining-positive sinusoid epithelial cell nuclei in the HTK group was higher than that in the UW group (not significant).

CONCLUSIONS

The histidine-tryptophan-ketoglutarate solution can be perfused with lower vascular resistance than the University of Wisconsin solution, reducing shear stress and preventing sinusoid epithelial cell injury in marginal grafts used as split-liver grafts.

Prediction of hypotension during the alveolar recruitment maneuver in spine surgery: a prospective observational study

BACKGROUND

Atelectasis can occur in many clinical practices. One way to prevent this complication is through the alveolar recruitment maneuver (ARM). However, hemodynamic compromise can accompany ARM. This study aims to predict ARM-induced hypotension using a non-invasive method.

METHODS

94 American Society of Anesthesiologists physical status I-II patients aged 19 to 75 with scheduled spinal surgery were enrolled. After anesthesia, we performed a stepwise ARM. Data on perfusion index, mean arterial pressure, heart rate, pleth variability index, cardiac index, and stroke volume variation was collected before induction of anesthesia (T0), just before ARM (T1), at the start of ARM (T2), 0.5 min (T3), 1 min (T4), 1.5 min (T5, end of ARM), and 2 min after the beginning of ARM (T6). Hypotension was defined as when the mean arterial pressure at T5 decreased by 20% or more compared to the baseline. The primary endpoint is that the perfusion index measuring before induction of anesthesia, which reflects the patients' own vascular tone, was correlated with hypotension during ARM.

RESULTS

Seventy-five patients (79.8%) patients developed hypotension during ARM. The pre-induction persufion index (Pi) (95% confidence interval) was 1.7(1.4-3.1) in the non-hypotension group and 3.4(2.4-3.9) in the hypotension group. (p < 0.004) The hypotension group showed considerably higher Pi than the non-hypotension group before induction. The decrease of Pi (%) [IQR] in the non-hypotensive group (52.8% [33.3-74.7]) was more significant than in the hypotensive group. (36% [17.6-53.7]) (p < 0.05) The area under the receiver operating characteristic curve of Pi for predicting hypotension during ARM was 0.718 (95% CI 0.615-0.806; p = 0.004), and the threshold value of the Pi was 2.4.

CONCLUSION

A higher perfusion index value measuring before induction of anesthesia can be used to predict the development of hypotension during ARM. Prophylactic management of the following hypotension during ARM could be considered in high baseline Pi patients.

Persistent pulmonary hypertension of the newborn: Historical perspectives

For many decades, persistent pulmonary hypertension of the newborn (PPHN) remained a baffling disorder, often confused with cyanotic congenital heart disease, with a very high mortality. Originally described as a condition characterized by clear lung fields and profound hypoxemia, modern diagnostic techniques and novel therapeutics have improved the outcomes of affected newborns. This paper will review the historical aspects of PPHN and enable the reader to see how far we have come but also how far we have to go in conquering this unique disorder.

The warfare for plant highway: vascular plant-microbe interaction pinpoints lignin

Plant vascular pathogens are one kind of destructive pathogens in agricultural production. However, mechanisms behind the vascular pathogen-recognition and the subsequent defense responses of plants are not well known. A recent pioneering study on plant vascular immunity discovered a conserved MKP1-MPK-MYB signaling cascade that activates lignin biosynthesis in vascular tissues to confer vascular resistance in both monocot rice and the dicot Arabidopsis. The breakthrough provides a novel view on plant immunity to vascular pathogens and offers a potential strategy for the future breeding of disease-resistant crops.

Dapagliflozin induces vasodilation in resistance-size mesenteric arteries by stimulating smooth muscle cell KV7 ion channels

Dapagliflozin is a sodium-glucose cotransporter 2 (SGLT2) inhibitor that, in addition to glucose reduction, lowers systemic blood pressure. Here, we investigated if dapagliflozin could directly relax small mesenteric arteries that control peripheral vascular resistance and blood pressure, and the underlying molecular mechanism. We used pressurized arterial myography, pharmacological inhibition and Western blotting to investigate the direct effect of dapagliflozin on the contractility of freshly isolated, resistance-size rat mesenteric arteries. Our pressure myography data unveiled that dapagliflozin relaxed small mesenteric arteries in a concentration-dependent manner. Non-selective inhibition of K_V channels and selective inhibition of smooth muscle cell voltage-gated K⁺ channels K_V7 attenuated dapagliflozin-induced vasorelaxation. Inhibition of other major K_V isoforms such as K_V1.3, K_V1.5 channels as well as large-conductance Ca²⁺-activated K⁺ (BK_Ca) channels, ATP-sensitive (K_ATP) channels did not abolish vasodilation. Dapagliflozin-evoked vasodilation remained unaltered by pharmacological inhibition of endothelium-derived nitric oxide (NO) signaling, prostacyclin (PGI₂), as well as by endothelium denudation. Our Western blotting data revealed that SGLT2 protein is expressed in rat mesenteric arteries. However, non-selective inhibition of SGLTs did not induce vasodilation, demonstrating that the vasodilatory action is independent of SGLT2 inhibition. Overall, our data suggests that dapagliflozin directly and selectively stimulates arterial smooth muscle cells K_V7 channels, leading to vasodilation in resistance-size mesenteric arteries. These findings are significant as it uncovers for the first time a direct vasodilatory action of dapagliflozin in resistance mesenteric arteries, which may lower systemic blood pressure.

Safety and efficacy of RT234 vardenafil inhalation powder on exercise parameters in pulmonary arterial hypertension: phase II, dose-escalation study design

BACKGROUND

Pulmonary arterial hypertension (PAH) is a progressive disease characterized by high mean pulmonary arterial pressure (≥ 20 mmHg) and remodeling of the vascular arteries. Approved therapies improve symptoms and delay clinical worsening in the long term, but they do not relieve acute exertional symptoms. RT234, a drug/device combination (Respira Therapeutics, Palo Alto, CA, USA) that delivers the phosphodiesterase 5 inhibitor vardenafil to the lungs via inhalation, has been shown to reduce pulmonary vascular resistance in patients with PAH. This study aims to evaluate whether RT234 can increase oxygen capacity during cardiopulmonary exercise testing (CPET) in patients with PAH.

METHODS

This prospective, multi-center, open-label, two-cohort, dose-escalation, phase IIb trial in patients with PAH will evaluate the safety and efficacy of RT234 in improving exercise parameters. The trial began in September 2020 and is expected to be completed by early 2024. Patients eligible for enrollment will have a right heart catheterization-confirmed diagnosis of PAH, a 6-minute walking distance of ≥ 150 m, a minute ventilation/carbon dioxide production slope of ≥ 36, and will be on up to three stable oral and/or inhaled (not parenteral) PAH-specific background therapies. The estimated sample size is 86 patients, who will be divided into two dose cohorts. Cohort 1 will receive 0.5 mg RT234, and cohort 2 will receive 1.0 mg RT234. Each cohort will contain two subgroups based on the number of PAH background medications (up to two vs three). The trial will assess patients' changes from baseline in peak oxygen consumption (VO₂) during CPET 30 minutes after a single dose of 0.5 mg or 1.0 mg RT234, the change in the 6-minute walking distance, and the pharmacokinetics and safety profile of single doses of RT234.

CONCLUSION

This is the first trial involving an as-needed medication for PAH. The trial will provide insights into the safety and efficacy of as-needed RT234 in treating the acute symptoms of PAH during exercise and will inform the design of further trials.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov identifier NCT04266197.

The cerebroplacental ratio: association with maternal hypertension and proteinuria

Objective

To evaluate the resistive indices (RIs) of the fetal umbilical and middle cerebral arteries, as well as to determine the cerebroplacental ratio (CPR), in fetuses of women with hypertension.

Materials and Methods

This was a comparative cross-sectional study involving 75 pregnant women with pregnancy-induced hypertension (PIH) and 75 apparently healthy pregnant women (control group), all of whom were submitted to Doppler ultrasound examination of the fetal middle cerebral and umbilical arteries between 20 and 40 weeks of gestation. The two groups were compared in terms of the RI of the middle cerebral and umbilical arteries, as well as the CPR. The level of statistical significance was set at p ≤ 0.05.

Results

The mean age was 32.4 ± 4.6 years in the PIH group and 32.6 ± 4.6 years in the control group (p = 0.633). The mean umbilical artery RI was significantly higher in the PIH group than in the control group (0.67 ± 0.14 vs. 0.61 ± 0.08; p = 0.012), whereas the mean middle cerebral artery RI was significantly higher in the control group (0.80 ± 0.05 vs. 0.76 ± 0.08; p = 0.001). Among the women in the PIH group, the mean CPR was significantly lower for those with proteinuria than for those without (1.07 ± 0.26 vs. 1.27 ± 0.22; p = 0.001).

Conclusion

Maternal hypertension during pregnancy appears to be associated with increased fetal umbilical artery RI and reduced fetal middle cerebral artery RI, as well as with a low CPR. In pregnant women, the combination of PIH and proteinuria is also apparently associated with an increased risk of a low CPR.

Reliability of a New Semi-automatic Image Analysis Method for Evaluating the Doppler Signal and Intratendinous Vascular Resistance in Patellar Tendinopathy

The aim of this study was to determine the intra- and inter-rater reliability of a new semi-automatic image analysis method for quantification of the shape of the Doppler signal and the intratendinous vascular resistance in patellar tendinopathy. Thirty athletes (27.4 y, standard deviation = 8.57 y) with patellar intratendinous vascularity were included in a cross-sectional study (42 tendons analyzed). The intratendinous blood flow was assessed with power Doppler and ImageJ (Version 1.50b, National Institutes of Health, Bethesda, MD, USA) quantification software over a manually selected region of interest. Two blinded observers performed the analysis of the Doppler signal (vascular resistance) and shape descriptors (number of signals, pixel intensity, area, perimeter, major diameter, minor diameter, circularity and solidity). The intraclass correlation coefficient (ICC) was calculated, and the Bland-Altman mean of differences (MoD) and 95% limits of agreement (LoA) were determined. Also, small real differences (SRDs) and the standard error of measurement (SEM) were calculated. Intra-rater reliability was at a maximum for area (ICC = 0.999, 95% confidence interval [CI] = 0.998-0.999) and at a minimum for solidity (ICC = 0.782, 95% CI: 0.682-0.853). The MoD and 95% LoA were very low, and the relative SRD and SEM were below 5.3% and 2%, respectively. The inter-rater reliability was the maximum for area (ICC = 0.993, 95% CI = 0.989-0.996) and the minimum for circularity (ICC = 0.73; 95% CI=0.611-0.817). The MoD and 95% LoA were low, with the SRD and SEM below 6% and 2.2%. The proposed quantitative method for studying the intratendinous Doppler signal in the patellar tendon is reliable and reproducible.

Acute ambient air pollution exposure and placental Doppler results in the NICHD fetal growth studies - Singleton cohort

BACKGROUND

Increased placental vascular resistance is a proposed mechanism by which air pollution exposure during pregnancy lowers birth weight and increases pregnancy-induced hypertensive disorders.

OBJECTIVE

To examine the impact of acute air pollution exposure during pregnancy on uterine and umbilical artery Doppler indicators of placental vascular resistance.

METHODS

After a first ultrasound to confirm gestational age, 2562 pregnant women recruited in 12 clinics throughout the United States underwent up to five standardized ultrasounds with Doppler measurements. Exposures to 11 air pollutants were estimated for the hour of ultrasound and each of the 2 h prior to ultrasound at the clinics using the National Air Quality Forecast Capability reanalysis products. We used mixed logistic regression to study the longitudinal odds ratio (OR) of any, uni- or bi-lateral systolic and diastolic uterine artery notching compared to no notching and the longitudinal OR of abnormal end diastolic flow of the umbilical artery compared to forward flow. Uterine and umbilical artery resistance indexes were studied using linear mixed models.

RESULTS

Each inter-quartile range (IQR) increase of particulate matter < 2.5 μm, nitrate, ammonium, primary organic matter (POM) and nitrogen dioxide during the hour of ultrasound was associated with a decreased risk of unilateral systolic notch and with increased resistance index of the left uterine artery. For the umbilical artery, each IQR increase in ozone was associated with decreased resistance index (b: -0.26, 95 % CI: -0.52, -0.01) and with a decreased risk of abnormal end diastolic flow (OR: 0.36, 95 % CI: 0.14, 0.94); while each IQR increase of elemental carbon and POM was associated with increased risk of abnormal end diastolic flow (OR: 1.47, 95 % CI: 1.02, 2.13 and OR: 1.67, 95 % CI: 1.17, 2.39, respectively).

DISCUSSION

Our results suggest acute air pollution exposure may influence placental vascular resistance.

Continuous gastric saline perfusion elicits cardiovascular responses in freshwater rainbow trout (Oncorhynchus mykiss)

When in seawater, rainbow trout (Oncorhynchus mykiss) drink to avoid dehydration and display stroke volume (SV) mediated elevations in cardiac output (CO) and an increased proportion of CO is diverted to the gastrointestinal tract as compared to when in freshwater. These cardiovascular alterations are associated with distinct reductions in systemic and gastrointestinal vascular resistance (R_Sys and R_GI, respectively). Although increased gastrointestinal blood flow (GBF) is likely essential for osmoregulation in seawater, the sensory functions and mechanisms driving the vascular resistance changes and other associated cardiovascular changes in euryhaline fishes remain poorly understood. Here, we examined whether internal gastrointestinal mechanisms responsive to osmotic changes mediate the cardiovascular changes typically observed in seawater, by comparing the cardiovascular responses of freshwater-acclimated rainbow trout receiving continuous (for 4 days) gastric perfusion with half-strength seawater (½ SW, ~ 17 ppt) to control fish (i.e., no perfusion). We show that perfusion with ½ SW causes significantly larger increases in CO, SV and GBF, as well as reductions in R_Sys and R_GI, compared with the control, whilst there were no significant differences in blood composition between treatments. Taken together, our data suggest that increased gastrointestinal luminal osmolality is sensed directly in the gut, and at least partly, mediates cardiovascular responses previously observed in SW acclimated rainbow trout. Even though a potential role of mechano-receptor stimulation from gastrointestinal volume loading in eliciting these cardiovascular responses cannot be excluded, our study indicates the presence of internal gastrointestinal milieu-sensing mechanisms that affect cardiovascular responses when environmental salinity changes.

Intercostal and vastus lateralis microcirculatory response to a sympathoexcitatory manoeuvre in patients with chronic obstructive pulmonary disease

Patients with COPD present with systemic vascular malfunctioning and their microcirculation is possibly more fragile to overcome an increase in the sympathetic vasoconstrictor outflow during sympathoexcitatory situations. To test the skeletal muscle microvascular responsiveness to sympathoexcitation, we asked patients with COPD and age- and sex-matched controls to immerse a hand in iced water [Cold Pressor Test (CPT)]. Near-infrared spectroscopy detection of the indocyanine green dye in the intercostal and vastus lateralis microcirculation provided a blood flow index (BFI). BFI divided by mean blood pressure (MBP) provided an index of microvascular conductance (BFI/MBP). The CPT decreased BFI and BFI/MBP in the intercostal (P = 0.01 and < 0.01, respectively) and vastus lateralis (P = 0.08 and 0.03, respectively) only in the COPD group, and the per cent BFI and BFI/MBP decrease was similar between muscles (P = 0.78 and 0.85, respectively). Thus, our findings support that sympathoexcitation similarly impairs intercostal and vastus lateralis microvascular regulation in patients with COPD.

Association of carotid ultrasonography with perioperative stroke after thoracic aortic aneurysm treatment: a retrospective study

PURPOSE

The purpose of this study was to verify whether carotid ultrasonography (CUS) findings could be associated with the occurrence of perioperative stroke after thoracic aortic aneurysm (TAA) treatment.

METHODS

Patients with TAAs who were treated by either total arch replacement or thoracic endovascular aortic repair (TEVAR) were retrospectively enrolled. Left subclavian artery (LSA) embolization and bypass surgery of the left common carotid artery (CCA) to the LSA before TEVAR were additionally performed for some patients. CUS was performed before TAA treatment to evaluate carotid atherosclerosis and flow velocities of bilateral cervical arteries. After dividing patients into those with and without perioperative stroke, their background, atherosclerotic risk factors, history of stroke, TAA location and size, treatment procedures, and CUS parameters were compared between the two groups.

RESULTS

Of the 60 patients (18 women, 42 men; mean age 73.5 ± 10.2 years) with TAA, four (7.5%) developed perioperative stroke. There were no significant differences in the patients' characteristics and their TAAs between those with and without perioperative stroke. For the CUS parameters, end-diastolic velocity (EDV) of bilateral CCAs was significantly decreased in perioperative stroke patients (with vs without stroke; right: 9.2 ± 1.8 vs. 14.5 ± 4.6 cm/s, P = 0.025, left: 9.1 ± 0.3 vs. 15.0 ± 4.5 cm/s, P = 0.012), whereas the resistance index (RI) of bilateral CCAs was significantly elevated (right: 0.76 vs. 0.87, P = 0.008, left: 0.76 vs. 0.87, P < 0.001).

CONCLUSIONS

Lower EDV and higher RI of bilateral CCAs were significantly associated with perioperative stroke after TAA treatment. Thus, CUS findings may help predict the occurrence of perioperative stroke.

Hypocholesterolemia is a risk factor for reduced systemic vascular resistance reactivity during hemodialysis

Intradialytic hypotension (IDH) is associated with high mortality. Peripheral vascular resistance and circulating blood volume are important factors in IDH; however, the effects of hemodialysis (HD) on vascular resistance in IDH remain unclear. We herein performed a retrospective observational cohort study to investigate changes in and factors related to vascular resistance during HD. A total of 101 HD patients were divided into two groups (Decreased blood pressure (BP) during HD group: N = 19, Nondecreased BP group: N = 82), and cardiac output was measured with electrical velocimetry (AESCLON) for 3 h. The systemic vascular resistance index (SVRI) was significantly decreased in the Decreased BP group, while the cardiac index was similar in both groups. A multivariate regression analysis identified hypocholesterolemia as a predictor of reduced vascular resistance reactivity during HD. Furthermore, a correlation was found between changes in the SVRI and cholesterol levels in patients with a higher Geriatric Nutritional Risk Index (GNRI) but not in those with a lower GNRI. The present results suggest that hypocholesterolemia contributes to reducing systematic vascular resistance reactivity during HD, which is an important predictor of a reduction in BP during HD. The relationship between hypocholesterolemia and vascular resistance may involve mechanisms other than malnutrition.

Changes in choroidal circulation and pulse waveform in a case of pregnancy-induced hypertension with serous retinal detachment

Purpose

We aimed to examine the changes in choroidal blood flow (CBF), choroidal pulse waveform, and central choroidal thickness (CCT) in a case of pregnancy-induced hypertension (PIH) using laser speckle flowgraphy (LSFG) and enhanced depth imaging optical coherence tomography (EDI-OCT) before and after treatment with antihypertensive drugs.

Observations

A 24-year-old Japanese woman diagnosed with PIH presented with complaints of worsening and blurred vision in the right eye. Funduscopic findings at the initial visit showed serous retinal detachment (SRD), retinal hemorrhage, and arterial tortuosity. The LSFG color map showed a warm color. Macular mean blur rate (MBR), which is an index of relative blood flow velocity, in both eyes was high, along with choroidal thickening. Blowout time (BOT), which indicates the rate of time in which the MBR is greater than half the amplitude during one heartbeat, was low and acceleration time index (ATI), which represents the time-to-peak of MBR, was high. Several weeks after treatment with antihypertensive drugs, the CBF and ATI gradually decreased with regression of the SRD and thinning of the CCT. On the other hand, BOT gradually increased after treatment, showing a significant decrease in vascular resistance. Ocular perfusion pressure decreased after treatment because of the reduction in blood pressure.

Conclusions and Importance

LSFG might reveal choroidal overperfusion and increased vascular resistance, along with SRD and choroidal thickening, in a patient with PIH with reversal after treatment with antihypertensive drugs. These findings demonstrate the importance of evaluation of ocular blood flow and vascular resistance in women with PIH in order to routinely assess the clinical and systemic condition.

Impact of Anesthetic and Ventilation Strategies on Invasive Hemodynamic Measurements in Pediatric Heart Transplant Recipients

BACKGROUND

Care of pediatric heart transplant recipients relies upon serial invasive hemodynamic evaluation, generally performed under the artificial conditions created by anesthesia and supportive ventilation.

OBJECTIVES

This study aimed to evaluate the hemodynamic impacts of different anesthetic and ventilatory strategies.

METHODS

We compared retrospectively the cardiac index, right- and left-sided filling pressures, and pulmonary and systemic vascular resistances of all clinically well and rejection-free heart transplant recipients catheterized from 2005 through 2017. Effects of spontaneous versus positive pressure ventilation and of sedation versus general anesthesia were tested with generalized linear mixed models for repeated measures using robust sandwich estimators of the covariance matrices. Least squared means showed adjusted mean outcome values, controlled for appropriate confounders.

RESULTS

720 catheterizations from 101 recipients met inclusion criteria. Adjusted cardiac index was 3.14 L/min/m² (95% CI 3.01-3.67) among spontaneously breathing and 2.71 L/min/m² (95% CI 2.56-2.86) among ventilated recipients (p < 0.0001). With spontaneous breathing, left filling pressures were lower (9.9 vs 11.0 mmHg, p = 0.030) and systemic vascular resistances were higher (24.0 vs 20.5 Woods units, p < 0.0001). After isolating sedated from anesthetized spontaneously breathing patients, the observed differences in filling pressures and resistances emerged as a function of sedation versus general anesthesia rather than of spontaneous versus positive pressure ventilation.

CONCLUSION

In pediatric heart transplant recipients, positive pressure ventilation reduces cardiac output but does not alter filling pressures or vascular resistances. Moderate sedation yields lower left filling pressures and higher systemic vascular resistances than does general anesthesia. Differences are quantitatively small.

Hemodynamic Phenotypes of Hypertension Based on Cardiac Output and Systemic Vascular Resistance

BACKGROUND

Blood pressure is a physiologic measure that reflects cardiac output and systemic vascular resistance. Classification by these components could be useful in characterizing subtypes of hypertension, which may have a role in selecting treatment strategies. However, hemodynamic phenotypes of a large, stable, outpatient population with hypertension remain unknown.

METHODS

We included 34,238 people with systolic blood pressure of ≥130 mm Hg, who underwent impedance cardiography at 51 sites of iKang Health Checkup Centers throughout China between 2012 and 2018. Hemodynamic parameters measured included stroke volume, stroke volume index, heart rate, cardiac output, cardiac index, systemic vascular resistance, and systemic vascular resistance index. We characterized these by systolic blood pressure categories and assessed patient characteristics associated with the ratio of cardiac index to systemic vascular resistance index.

RESULTS

Among the study cohort (n = 33,414; mean age 52 ± 13 years; 36.6% female), 49%, 40%, and 11% had systolic blood pressure130-139, 140-159, and ≥160 mm Hg, respectively. Among patients with systolic blood pressure 140-159 mm Hg, 9353 (70%) had high systemic vascular resistance index but normal/low cardiac index, 1949 (15%) had high cardiac index but low/normal systemic vascular resistance index, and 2053 (15%) had low/normal cardiac index and systemic vascular resistance index. Using multivariable analysis, we found that cardiac index to systemic vascular resistance index ratio was negatively associated with age and body mass index (all P <0.05; R-square 0.16, 0.12, and 0.09 for systolic blood pressure 130-139, 140-159 and ≥160 mm Hg, respectively).

CONCLUSIONS

Different hemodynamic blood pressure phenotypes were identified across all hypertensive blood pressure categories. Although individual characteristics were associated with the cardiac index to systemic vascular resistance index ratio, they only weakly explained the variation.

Central hemodynamics are associated with fetal outcomes in pregnancies of advanced maternal age

OBJECTIVES

Age is a known risk factor for both maternal cardiovascular disease and adverse outcomes in pregnancy. We aimed to characterize the hemodynamic profiles in pregnancies of advanced maternal age (AMA) and correlate these with fetal outcomes.

STUDY DESIGN

This was a prospective observational study of pregnancies undergoing antenatal testing. Maternal hemodynamics were measured non-invasively using an imaging probe at the descending aorta and the Uscom BP + arm cuff utilizing pulse pressure wave analysis. The Wilcoxon rank-sum test, Fisher's exact test, and Spearman rank correlation test were used for statistical analysis in R.

MAIN OUTCOME MEASURES

Hemodynamic measurements, neonatal birthweight.

RESULTS

Twenty-one AMA and twenty-four control patients were enrolled. Mean age ± SD was 39 ± 3.22 in the AMA cohort and 28 ± 4.32 in the control cohort (p < 0.001). AMA patients were evaluated at a later gestational age (36 4/7 weeks) compared to control (34 1/7 weeks, p = 0.02). Between groups, there was no difference in BMI, race, hypertensive disease, diabetes, asthma, drug use, or indication for antenatal testing. 38% (AMA) and 37% (control) had hypertensive disorders of pregnancy. In AMA patients but not control patients, cardiac output (r = 0.52, p = 0.01), systemic vascular resistance (r = -0.53, p = 0.01), and systemic vascular resistance index (r = -0.62, p = 0.002) were significantly correlated with neonatal birthweight percentile.

CONCLUSIONS

Hemodynamic alterations consistent with a low output, high resistance cardiovascular circuit were associated with lower birthweight in AMA, but not in control pregnancies.

Effects of Cross-Clamping on Vascular Mechanics: Comparing Waveform Analysis With a Numerical Model

BACKGROUND

Immediate changes in vascular mechanics during aortic cross-clamping remain widely unknown. By using a numerical model of the arterial network, vascular compliance and resistance can be estimated and the time constant of pressure waves can be calculated and compared with results from the classic arterial waveform analysis.

METHODS

Experimental data were registered from continuous invasive radial artery pressure measurements from 11 patients undergoing vascular surgery. A stable set of beats were chosen immediately before and after each clamping event. Through the arterial waveform analysis, the time constant was calculated for each individual beat and for a mean beat of each condition as to compare with numerical simulations. Overall proportional changes in resistance and compliance during clamping and unclamping were calculated using the numerical model.

RESULTS

Arterial waveform analysis of individual beats indicated a significant 10% median reduction in the time constant after clamping, and a significant 17% median increase in the time constant after unclamping. There was a positive correlation between waveform analysis and numerical values of the time constant, which was moderate (ρ = 0.51; P = 0.01486) during clamping and strong (ρ = 0.77; P ≤ 0.0001) during unclamping. After clamping, there was a significant 16% increase in the mean resistance and a significant 23% decrease in the mean compliance. After unclamping, there was a significant 19% decrease in the mean resistance and a significant 56% increase in the mean compliance.

CONCLUSIONS

There are significant hemodynamic changes in vascular compliance and resistance during aortic clamping and unclamping. Numerical computer models can add information on the mechanisms of injury due to aortic clamping.

An integrative review of the literature on in-hospital worsening heart failure

A subset of patients hospitalized for acute exacerbation of chronic heart failure develop in-hospital worsening heart failure. The objective of this paper is to present an integrative review of in-hospital worsening heart failure, including definitions, incidence, prevalence, mechanisms, treatments, outcomes, and early identification by providers. A search of electronic databases was conducted from January 2000-August 2017 using multiple search terms. Papers were reviewed for relevance; retained papers were abstracted and data were reported in a narrative synthesis. Twenty papers were selected. Many papers were observational data from in-hospital events that occurred during research trials. There was great variability in in-hospital worsening heart failure definition, incidence, prevalence, and treatments offered. Despite rescue therapies, in-hospital worsening heart failure was associated with increased risk for longer hospital stays, higher readmission rates, and death. To date, there are no therapies that target the underlying mechanisms or minimize its occurrence.

Adolescent habitual caffeine consumption and hemodynamic reactivity during rest, psychosocial stress, and recovery

OBJECTIVE

Most adolescents regularly consume caffeine. Whereas observational studies have suggested that coffee may be cardio-protective, pharmacological experimentation with adults shows that caffeine at dietary doses increases blood pressure, thereby implicating regular caffeine consumption as a potential source of harm for cardiovascular health. The present study was in response to the dearth of caffeine research among younger consumers. It was hypothesised that compared to the consumption of little or no caffeine, adolescents who habitually consume caffeine have overall higher blood pressure and increased vascular resistance.

METHOD

Using a quasi-experimental design, continuous measurements of blood pressure, cardiac output, and total peripheral resistance were taken non-invasively from adolescents (n = 333) aged 14-15 years and 18-19 years who reported "low", "moderate", or "high" levels of caffeine intake. Measurements were conducted when participants generally had negligible or low systematic caffeine levels while at rest, during stress, and during recovery from stress.

RESULTS

Whereas habitual caffeine consumption did not predict blood pressure level, higher caffeine intake was associated with modestly increased vascular resistance during all phases of the experiment (i.e., at rest, during stress, and during recovery from stress).

CONCLUSIONS

Present findings are important because they suggest that early exposure to caffeine may lead to persistent increases in vascular resistance, which in turn is an acknowledged risk factor for the development of hypertension. These results highlight the need for further studies of adolescents to determine the robustness of any persistent caffeine-related hemodynamic effects, and the implications such effects could have for long-term cardiovascular health.

TNF-alpha inhibition could reduce biomarkers of endothelial dysfunction in patients with moderate to severe psoriasis: A 52-week echo-Doppler based quasi-experimental study

OBJECTIVES

Psoriasis is associated to endothelial dysfunction, which causes impaired vascular functioning. TNF-α blockers have shown the ability to improve vascular functioning in psoriasis. The nailfold vessel resistance index (NVRI) assesses microvascular functioning at nailfold. The objectives of the study is to assess the effect of the TNF-α inhibition with adalimumab on NVRI.

MATERIAL AND METHODS

Quasi-experimental study. Fifteen patients with moderate-severe psoriasis received adalimumab 40mg sc according to label information. Participants were assessed at baseline and at 12, 24 and 52 weeks after study intervention.

RESULTS

A reduction of -0.09±0.02 (P<.01) in NVRI and a -11.2±2,41ng/ml (P<.001) in E-selectin was observed at week 52.

CONCLUSIONS

Adalimumab could produce a progressive and sustained reduction of vessel resistance at nailfold and E-selectin in patients with psoriasis.

Midazolam increases preload dependency during endotoxic shock in rabbits by affecting venous vascular tone

Background

Septic patients often require sedation in intensive care unit, and midazolam is one of the most frequently used sedatives among them. But the interaction between midazolam and septic shock is not known. The aim of this study is to investigate the effects of midazolam on preload dependency in an endotoxic shock model by evaluating systemic vascular tone and cardiac function.

Methods

Eighteen rabbits were randomly divided into three groups: Control group, MID1 group and MID2 group. Rabbits underwent ketamine anaesthesia and mechanical ventilation, and haemodynamic assessments were recorded in three groups (T0). Endotoxic shock was induced by lipopolysaccharide intravenously, and fluid resuscitation and norepinephrine were administered to obtain the baseline mean arterial pressure (MAP) (T1). Rabbits received equivalent normal saline (Control) and two consecutive dosages of midazolam: 0.3 mg kg⁻¹ h⁻¹ (MID1) and 3 mg kg⁻¹ h⁻¹ (MID2) (T2). Rabbits received another round of fluid challenge and norepinephrine infusion to return the MAP to normal (T3).

Results

No significant differences in haemodynamic parameters were observed in three groups at T0, T1 or T3. Midazolam infusion significantly increased pulse pressure variation (PPV) and stroke volume variation (SVV) compared to the values in Control group, and MAP, central venous pressure (CVP), mean systemic filling pressure (Pmsf) and cardiac output (CO) decreased at T2. Same effects were observed with increasing doses of midazolam, and resistance for venous return (Rvr) decreased (MID1 vs. MID2) at T2. PPV and SVV increased significantly at T2 compared to the values at T1. MAP, CVP, Pmsf and CO decreased in MID1 and MID2 groups. Rvr also decreased in MID2 group (T2 vs. T1). Midazolam did not affect cardiac function index, systemic vascular resistance or artery resistance (T2 vs. T1).

Conclusions

Midazolam administration promoted preload dependency in septic shock models via decreased venous vascular tone without affecting cardiac function.

The timeline of blood pressure changes and hemodynamic responses during an experimental noise exposure

BACKGROUND

Noise exposure increases blood pressure and peripheral vascular resistance in both genders in an experimental setting, as previously reported by the authors.

OBJECTIVES

The aim of this re-analysis was to present the minute-by-minute timeline of blood pressure changes and hemodynamic events provoked by traffic noise in the young and healthy adults.

METHODS

The experiment consisted of three 10-min phases: rest in quiet conditions before noise (Leq = 40 dBA), exposure to recorded road-traffic noise (Leq = 89 dBA), and rest in quiet conditions after noise (Leq = 40 dBA). Participants' blood pressure, heart rate, and hemodynamic parameters (cardiac index and total peripheral resistance index) were concurrently measured with a thoracic bioimpedance device. The raw beat-to-beat data were collected from 112 participants, i.e., 82 women and 30 men, aged 19-32 years. The timeline of events was created by splitting each experimental phase into ten one-minute intervals (30 intervals in total). Four statistical models were fitted to answer the six study questions what is happening from one minute to another during the experiment.

RESULTS

Blood pressure decreased during quiet phase before noise, increased in the first minute of noise exposure and then decreased gradually toward the end of noise exposure, and continued to decline to baseline values after noise exposure. The cardiac index showed a gradual decrease throughout the experiment, whereas total vascular resistance increased steadily during and after noise exposure.

CONCLUSIONS

The timeline of events in this 30-min experiment provides insight into the hemodynamic processes underlying the changes of blood pressure before, during and after noise exposure.

Understanding the Haemodynamics of Hypertension

PURPOSE OF REVIEW

This article introduces the haemodynamic principles that underpin the pathophysiology of hypertension and introduces a rational physiological approach to appropriate pharmacologic treatment.

RECENT FINDINGS

Outdated understanding of haemodynamics based on previous measurement systems can no longer be applied to our understanding of the circulation. We question the current view of hypertension as defined by a predominantly systolic blood pressure and introduce the concept of vasogenic, cardiogenic and mixed-origin hypertension. We postulate that failure to identify the individual's haemodynamic pattern may lead to the use of inappropriate medication, which in turn may be a major factor in patient non-compliance with therapeutic strategies. A population-based approach to treatment of hypertension may lead to suboptimal functional dynamics in the individual patient. Finally, we question the validity of current guidelines and published evidence relating morbidity and mortality to the future treatment of hypertension. The importance of individual haemodynamic profiles may be pivotal in the understanding, diagnosis and treatment of hypertension if optimal control with minimal adverse effects is to be achieved. Research based on individual haemodynamic patterns is overdue.

DIAGNOSTIC VALUE OF DUPLEX DOPPLER ULTRASOUND PARAMETERS IN PAPILLARY THYROID CARCINOMA

Context

Papillary thyroid carcinoma (PTC) is the most common type of thyroid cancer due to its high fibrotic content; it can affect the blood flow resistance.

Objective

To introduce duplex Doppler ultrasonography (DDUS) parameters of papillary thyroid carcinoma (PTC) and their correlation with size.

Design

The study was designed as a prospective study.

Subjects and Methods

Thyroid nodules of the patients who were already scheduled for thyroid surgery either for malignant thyroid nodules or multinodular goiter were evaluated for DDUS parameters. Size, systolic to diastolic flow velocity (S/D) ratio, pulsatility index (PI), and resistive index (RI) of each nodule were recorded. Nodules were diagnosed as PTC or benign nodules based on histopathology. DDUS parameters were compared between PTCs versus benign nodules and micro PTCs (≤ 10 mm) versus large PTCs (> 10 mm). A correlation analysis was performed between the size and DDUS parameters.

Results

140 thyroid nodules (30 PTCs, 110 benign nodules) were obtained. The mean S/D ratio, PI, and RI values were significantly higher in PTC than in benign nodules (p values were 0.0001, 0.0003, and 0.0001 respectively). The optimal cut-off values of S/D (0.732), PI (0.732), and RI (0.738) had accuracy rates of 71%, 69%, and 69%, respectively. There was no statistically significant difference between micro PTC and large PTC with regards to DDUS parameters. The size and DDUS parameters of PTC showed no significant correlation.

Conclusions

PTC has a high resistive flow pattern regardless of its size; however the clinical utility of DDUS to differentiate a PTC from benign nodule is limited.

Ex Vivo Dual Perfusion of the Human Placenta: Disease Simulation, Therapeutic Pharmacokinetics and Analysis of Off-Target Effects

In recent years ex vivo dual perfusion of the human placental lobule is seeing an international renaissance in its application to understanding fetal health and development. Here, we discuss the methods and uses of this technique in the evaluation of (1) vascular function, (2) transplacental clearance, (3) hemodynamic and oxygenation changes associated with pregnancy complications on placental structure and function, and (4) placental toxicology and post-perfusion evaluation of tissue architecture.

Where Is the "Optimal" Fontan Hemodynamics?

Fontan circulation is generally characterized by high central venous pressure, low cardiac output, and slightly low arterial oxygen saturation, and it is quite different from normal biventricular physiology. Therefore, when a patient with congenital heart disease is selected as a candidate for this type of circulation, the ultimate goals of therapy consist of 2 components. One is a smooth adjustment to the new circulation, and the other is long-term circulatory stabilization after adjustment. When either of these goals is not achieved, the patient is categorized as having "failed" Fontan circulation, and the prognosis is dismal. For the first goal of smooth adjustment, a lot of effort has been made to establish criteria for patient selection and intensive management immediately after the Fontan operation. For the second goal of long-term circulatory stabilization, there is limited evidence of successful strategies for long-term hemodynamic stabilization. Furthermore, there have been no data on optimal hemodynamics in Fontan circulation that could be used as a reference for patient management. Although small clinical trials and case reports are available, the results cannot be generalized to the majority of Fontan survivors. We recently reported the clinical and hemodynamic characteristics of early and late failing Fontan survivors and their association with all-cause mortality. This knowledge could provide insight into the complex Fontan pathophysiology and might help establish a management strategy for long-term hemodynamic stabilization.

Relevance of Haemodynamics in Treating Pre-eclampsia

Blood pressure is a way of describing the end result of changes in cardiac output, intravascular volume and peripheral resistance. It has certain advantages in that it is a reproducible and easily measured parameter, but in itself, it offers only a limited understanding of the underlying haemodynamics. In pregnancy, profound haemodynamic changes occur and in hypertensive diseases of pregnancy defining a condition by blood pressure alone risks missing the underlying cause. Partly, this has been a problem of ascribing the cause of hypertensive syndromes to the placenta which has inhibited rigorous research into other possible causes of haemodynamic dysfunction. It is becoming increasingly evident that hypertension in pregnancy may be associated with primarily high cardiac output or high peripheral resistance. A knowledge of the underlying type of hypertension may allow more rational treatment of these conditions in pregnancy rather than therapeutic attempts at controlling blood pressure by any means possible as an end in itself.

Aerobic interval training reduces vascular resistances during submaximal exercise in obese metabolic syndrome individuals

PURPOSE

The aim of this study was to determine the effects of high-intensity aerobic interval training (AIT) on exercise hemodynamics in metabolic syndrome (MetS) volunteers.

METHODS

Thirty-eight, MetS participants were randomly assigned to a training (TRAIN) or to a non-training control (CONT) group. TRAIN consisted of stationary interval cycling alternating bouts at 70-90% of maximal heart rate during 45 min day^-1 for 6 months.

RESULTS

CONT maintained baseline physical activity and no changes in cardiovascular function or MetS factors were detected. In contrast, TRAIN increased cardiorespiratory fitness (14% in VO_2PEAK; 95% CI 9-18%) and improved metabolic syndrome (-42% in Z score; 95% CI 83-1%). After TRAIN, the workload that elicited a VO₂ of 1500 ml min^-1 increased 15% (95% CI 5-25%; P < 0.001). After TRAIN when subjects pedaled at an identical submaximal rate of oxygen consumption, cardiac output increased by 8% (95% CI 4-11%; P < 0.01) and stroke volume by 10% (95% CI, 6-14%; P < 0.005) being above the CONT group values at that time point. TRAIN reduced submaximal exercise heart rate (109 ± 15-106 ± 13 beats min^-1; P < 0.05), diastolic blood pressure (83 ± 8-75 ± 8 mmHg; P < 0.001) and systemic vascular resistances (P < 0.01) below CONT values. Double product was reduced only after TRAIN (18.2 ± 3.2-17.4 ± 2.4 bt min^-1 mmHg 10^-3; P < 0.05).

CONCLUSIONS

The data suggest that intense aerobic interval training improves hemodynamics during submaximal exercise in MetS patients. Specifically, it reduces diastolic blood pressure, systemic vascular resistances, and the double product. The reduction in double product, suggests decreased myocardial oxygen demands which could prevent the occurrence of adverse cardiovascular events during exercise in this population. CLINICALTRIALS.

GOV IDENTIFIER

NCT03019796.

Cardiovascular effects of histamine in three widely diverse species of reptiles

The cardiovascular system of vertebrates is regulated by a vast number of regulatory factors, including histamine. In pythons, histamine induces a strong tachycardia and dilates the systemic vasculature, which resembles the cardiovascular response to the elevated metabolic rate during digestion. In fact, there is an important role of increased histaminergic tone on the heart during the initial 24 h of digestion in pythons. Whilst the cardiovascular effects of histamine are well studied in pythons, little is known about the effects in other groups of reptiles. The histaminergic effects on the heart vary among species and histamine may exert either pressor and depressor effects by causing either constrictive or dilatory vascular responses. Here, we investigated the cardiovascular effects of histamine in three species of reptiles with very different cardiovascular and pulmonary morphologies. Experiments were performed on both anesthetized and recovered animals. We show a species-dependent effect of histamine on the systemic vasculature with dilation in rattlesnakes and constriction in turtles and caimans but no effect on the pulmonary circulation. The histamine-induced dilation in rattlesnakes was mediated through an activation of H₂-receptors, whereas the histamine-induced constriction in caimans was mediated through both adrenergic signaling and H₁-receptors activation. In all three species, histamine-induced tachycardia by direct stimulation of histaminergic receptors as well as an indirect activation of adrenoreceptors. This finding highlights a more complex mechanism underlying the action of histamine than previously recognized in reptiles.

The Circulatory System in Liver Disease

In the cirrhotic liver, distortion of the normal liver architecture is caused by structural and vascular changes. Portal hypertension is often associated with a hyperdynamic circulatory syndrome in which cardiac output and heart rate are increased and systemic vascular resistance is decreased. The release of several vasoactive substances is the primary factor involved in the reduction of mesenteric arterial resistance, resulting in sodium and water retention with eventual formation of ascites. Management of these patients with acute cardiac dysfunction often requires invasive hemodynamic monitoring in an intensive care unit setting to tailor decisions regarding use of fluids and vasopressors.

Valved patch closure of aortopulmonary window

The case of an 8-year-old boy with an aortopulmonary window who underwent unidirectional valved patch closure of the window is described. The advantages of unidirectional valved patch closure in this setting are discussed.

Commentary on: "Vascular distensibilities have minor effects on intracardiac shunt patterns in reptiles" by Filogonio et al. (2017)

The recent study by Filogonio et al. (2017) suggested that net cardiac shunt patterns in two species of reptiles (Trachemys scripta and Crotalus durissus) were not significantly influenced by the vascular distensibilities of the systemic and pulmonary vasculatures. This is in contrast to a previously published study (Hillman et al., 2014) in the toad (Rhinella marina) in which net cardiac shunts were predicted primarily by the physical properties of vascular distensibility rather than physiological control of resistance of the systemic and pulmonary vasculature. We analyze the data and conclusions reached by Filogonio et al. (2017) regarding the role of vascular distensibilities in determining net cardiac shunt patterns in reptiles in comparison with toads. In our view, the conclusions reached by Filogonio et al. (2017) are not supported by the data primarily because vascular distensibilities were not measured in the reptiles analyzed in their study.

Effect of nitric oxide on renal autoregulation during hypothermia in the rat

Hypothermia-induced reduction of metabolic rate is accompanied by depression of both glomerular perfusion and filtration. The present study investigated whether these changes are linked to changes in renal autoregulation and nitric oxide (NO) signalling. During hypothermia, renal blood flow (RBF) and glomerular filtration rate (GFR) were reduced and urine production was increased, and this was linked with reduced plasma cGMP levels and increased renal vascular resistance. Although stimulation of NO production decreased vascular resistance, blood pressure and urine flow, intravenous infusion of the NO precursor L-arginine or the NO donor sodium nitroprusside did not alter RBF or GFR. In contrast, inhibition of NO synthesis by N^w-nitro-L-arginine led to a further decline in both parameters. Functional renal autoregulation was apparent at both temperatures. Below the autoregulatory range, RBF in both cases increased in proportion to the perfusion ±pressure, although, the slope of the first ascending limb of the pressure-flow relationship was lower during hypothermia. The main difference was rather that the curves obtained during hypothermia levelled off already at a RBF of 3.9 ± 0.3 mL/min then remained stable throughout the autoregulatory pressure range, compared to 7.6 ± 0.3 mL/min during normothermia. This was found to be due to a threefold increase in, primarily, the afferent arteriolar resistance from 2.6 to 7.5 mmHg min mL⁻¹. Infusion of sodium nitroprusside did not significantly affect RBF during hypothermia, although a small increase at pressures below the autoregulatory range was observed. In conclusion, cold-induced rise in renal vascular resistance results from afferent arteriolar vasoconstriction by the autoregulatory mechanism, setting RBF and GFR in proportion to the metabolic rate, which cannot be explained by reduced NO production alone.

Automated oscillometric blood pressure and pulse-wave acquisition for evaluation of vascular stiffness in atherosclerosis

OBJECTIVE

Evaluation of diagnostic accuracy of an oscillometry-based device (VascAssist) combining fully automated ankle-brachial index (ABI) and pulse-wave velocity (PWV) assessment for detection of peripheral arterial disease (PAD).

SUBJECTS AND METHODS

110 consecutive subjects including symptomatic PAD patients (n = 41) and healthy PAD-free participants (n = 69) were recruited. All subjects underwent standard manual Doppler-based ABI (sABI) and oscillometry-based automated ABI (aABI) measurements (VascAssist). Oscillometry by the VascAssist included central and peripheral PWV assessment. Additionally, arterial stiffness (AS) was evaluated by flow-mediated vasodilation (FMD) of the brachial artery in all patients. All symptomatic PAD patients underwent catheter angiography for endovascular intervention and post-interventional acquisition of sABI, aABI, PWV and FMD.

RESULTS

Sensitivity, specificity, PPV and NPV of aABI for detecting PAD was 73%, 100%, 100%, and 86% as compared to 80%, 96%, 92%, and 89% for sABI. Pearson-correlation for diabetics was r = 0.81; (P < .001) and for non-diabetics r = 0.77; (P < .001). Bland-Altman-analysis revealed a difference (95% CI) for diabetics of 0.09 (-0.22-0.4] and non-diabetics 0.022 [-0.25-0.295]. Weak correlation exists for FMD/AS analysis (pre-interventional R = 0.386, P = .043; post-interventional R = -0.06; P = .76) and significant increase of pre-/post-interventional PWV analysis (P < .001).

CONCLUSION

Combined automatic ABI and PWV acquisition with the VascAssist device showed excellent diagnostic accuracy for detection of PAD. Compared to FMD, AS analysis may serve as an investigator-independent (screening) tool for determination of functional vascular damage in atherosclerosis.

Accelerometer-determined physical activity and the cardiovascular response to mental stress in children

OBJECTIVES

Cardiovascular reactivity has been associated with future hypertension and cardiovascular mortality. Higher physical activity (PA) has been associated with lower cardiovascular reactivity in adults, but little data is available in children. The purpose of this study was to examine the relationship between PA and cardiovascular reactivity to mental stress in children.

DESIGN

Cross-sectional study.

METHODS

This study sample included children from the Oswego Lead Study (n=79, 46% female, 9-11 years old). Impedance cardiography was performed while children participated in a stress response protocol. Children were also asked to wear Actigraph accelerometers on their wrists for 3 days to measure intensity and duration of PA and sedentary time.

RESULTS

In multivariable models, moderate to vigorous (MV) PA was associated with lower body mass index (BMI) percentile and lower total peripheral resistance (TPR) response to stress (beta=-0.025, p=0.02; beta=-0.009, p=0.05). After additional adjustment for BMI, MVPA was also associated with lower diastolic blood pressure response to stress (beta=-0.01, p=0.03). Total PA and sedentary time were not associated with BMI or cardiovascular responses to stress.

CONCLUSIONS

A modest, inverse relation of PA to vascular reactivity to mental stress was observed in children. These data provide confirmatory evidence that the promotion of PA recommendations for children are important for cardiovascular health.

Initial orthostatic hypotension in teenagers and young adults

Objective

To assess: (1) the frequency of an abnormally large fall in blood pressure (BP) upon standing from supine in patients with initial orthostatic hypotension (IOH); (2) the underlying hemodynamic mechanisms of this fall in BP upon standing from supine and from squatting.

Methods

In a retrospective study of 371 patients (≤30 years) visiting the syncope unit, the hemodynamic response to standing and squatting were studied in 26 patients who were diagnosed clinically with IOH, based on history taking only. In six patients changes in cardiac output (CO) and systemic vascular resistance (SVR) were determined, and the underlying hemodynamics were analyzed.

Results

15/26 (58 %) patients with IOH had an abnormally large initial fall in systolic BP (≥40 mmHg). There was a large scatter in CO and SVR response after arising from supine [ΔCO at BP nadir median −8 % (range −37, +27 %); ΔSVR at BP nadir median −31 % (range −46, +10 %)]. The hemodynamic response after squatting showed a more consistent pattern, with a fall in SVR in all six patients [ΔCO at BP nadir median +23 % (range −12, +31 %); ΔSVR at BP nadir median −42 %, (range −52, −35 %)].

Interpretation

The clinical diagnosis of IOH is based on history taking, as an abnormally large fall in systolic BP can only be documented in 58 %. For IOH upon standing after supine rest, the hemodynamic mechanism can be either a large fall in CO or in SVR. For IOH upon arising from squatting a large fall in SVR is a consistent finding.

Behavior of vascular resistance undergoing various pressure insufflation and perfusion on decellularized lungs

Bioengineering of functional lung tissue by using whole lung scaffolds has been proposed as a potential alternative for patients awaiting lung transplant. Previous studies have demonstrated that vascular resistance (Rv) could be altered to optimize the process of obtaining suitable lung scaffolds. Therefore, this work was aimed at determining how lung inflation (tracheal pressure) and perfusion (pulmonary arterial pressure) affect vascular resistance. This study was carried out using the lungs excised from 5 healthy male Sprague-Dawley rats. The trachea was cannulated and connected to a continuous positive airway pressure (CPAP) device to provide a tracheal pressure ranging from 0 to 15cmH2O. The pulmonary artery was cannulated and connected to a controlled perfusion system with continuous pressure (gravimetric level) ranging from 5 to 30cmH2O. Effective Rv was calculated by ratio of pulmonary artery pressure (PPA) by pulmonary artery flow (V'PA). Rv in the decellularized lungs scaffolds decreased at increasing V'PA, stabilizing at a pulmonary arterial pressure greater than 20cmH2O. On the other hand, CPAP had no influence on vascular resistance in the lung scaffolds after being subjected to pulmonary artery pressure of 5cmH2O. In conclusion, compared to positive airway pressure, arterial lung pressure markedly influences the mechanics of vascular resistance in decellularized lungs.

Evidence-based versus pathophysiology-based approach to diagnosis and treatment of neonatal cardiovascular compromise

With the advances in biomedical research and neonatal intensive care, our understanding of cardiovascular developmental physiology and pathophysiology has significantly improved during the last few decades. Despite this progress, the current management of circulatory compromise depends primarily on experts' opinions rather than high level of evidence. The lack of reliable, accurate, continuous and preferably non-invasive monitoring techniques has further limited our ability to collect the information needed for the design and execution of more sophisticated clinical trials with a better chance to provide the evidence we need. Given the lack of randomized, placebo-controlled trials investigating clinically relevant outcomes of novel treatments of neonatal cardiovascular compromise, we must now use the available lower level of evidence and our present understanding of developmental physiology and pathophysiology when providing cardiovascular supportive care to critically ill neonates. However, with recent advances in cardiovascular monitoring capabilities, direct and more objective assessment of the changes in cardiovascular function, organ blood flow, and tissue oxygenation have become possible. These advances have helped in our clinical assessment and enabled us to start designing more sophisticated interventional clinical trials using clinically relevant endpoints.

Minimally invasive monitoring

Although use of the classic pulmonary artery catheter has declined, several techniques have emerged to estimate cardiac output. Arterial pressure waveform analysis computes cardiac output from the arterial pressure curve. The method of estimating cardiac output for these devices depends on whether they need to be calibrated by an independent measure of cardiac output. Some newer devices have been developed to estimate cardiac output from an arterial curve obtained noninvasively with photoplethysmography, allowing a noninvasive beat-by-beat estimation of cardiac output. This article describes the different devices that perform pressure waveform analysis.

The role of pulmonary arterial stiffness in COPD

COPD is the second most common cause of pulmonary hypertension, and is a common complication of severe COPD with significant implications for both quality of life and mortality. However, the use of a rigid diagnostic threshold of a mean pulmonary arterial pressure (mPAP) of ≥25mHg when considering the impact of the pulmonary vasculature on symptoms and disease is misleading. Even minimal exertion causes oxygen desaturation and elevations in mPAP, with right ventricular hypertrophy and dilatation present in patients with mild to moderate COPD with pressures below the threshold for diagnosis of pulmonary hypertension. This has significant implications, with right ventricular dysfunction associated with poorer exercise capability and increased mortality independent of pulmonary function tests.

The compliance of the pulmonary artery (PA) is a key component in decoupling the right ventricle from the pulmonary bed, allowing the right ventricle to work at maximum efficiency and protecting the microcirculation from large pressure gradients. PA stiffness increases with the severity of COPD, and correlates well with the presence of exercise induced pulmonary hypertension. A curvilinear relationship exists between PA distensibility and mPAP and pulmonary vascular resistance (PVR) with marked loss of distensibility before a rapid rise in mPAP and PVR occurs with resultant right ventricular failure. This combination of features suggests PA stiffness as a promising biomarker for early detection of pulmonary vascular disease, and to play a role in right ventricular failure in COPD. Early detection would open this up as a potential therapeutic target before end stage arterial remodelling occurs.

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Pulmonary hypertension is common in COPD.

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Right ventricular remodeling occurs at pressures below the diagnostic threshold of PH.

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Pulmonary arterial stiffening occurs early in the development of PH.

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Non-invasive measurement of pulmonary stiffness may serve as an early biomarker of PH.

Recombinant interleukin-1β dilates steelhead trout coronary microvessels: effect of temperature and role of the endothelium, nitric oxide and prostaglandins

Interleukin (IL)-1β is associated with hypotension and cardiovascular collapse in mammals during heat stroke, and the mRNA expression of this pro-inflammatory cytokine increases dramatically in the blood of Atlantic cod (Gadus morhua) at high temperatures. These data suggest that release of IL-1β at high temperatures negatively impacts fish cardiovascular function and could be a primary determinant of upper thermal tolerance in this taxa. Thus, we measured the concentration-dependent response of isolated steelhead trout (Oncorhynchus mykiss) coronary microvessels (<150 μm in diameter) to recombinant (r) IL-1β at two temperatures (10 and 20°C). Recombinant IL-1β induced a concentration-dependent vasodilation with vessel diameter increasing by approximately 8 and 30% at 10(-8) and 10(-7) mol l(-1), respectively. However, this effect was not temperature dependent. Both vessel denudation and cyclooxygenase blockade (by indomethacin), but not the nitric oxide (NO) antagonist L-NIO, inhibited the vasodilator effect of rIL-1β. In contrast, the concentration-dependent dilation caused by the endothelium-dependent calcium ionophore A23187 was completely abolished by L-NIO and indomethacin, suggesting that both NO and prostaglandin signaling mechanisms exist in the trout coronary microvasculature. These data: (1) are the first to demonstrate a functional link between the immune and cardiovascular systems in fishes; (2) suggest that IL-1β release at high temperatures may reduce systemic vascular resistance, and thus, the capacity of fish to maintain blood pressure; and (3) provide evidence that both NO and prostaglandins play a role in regulating coronary vascular tone, and thus, blood flow.