Plasma Proteomics Identifies B2M as a Regulator of Pulmonary Hypertension in Heart Failure With Preserved Ejection Fraction.

BACKGROUND: Pulmonary hypertension (PH) represents an important phenotype in heart failure with preserved ejection fraction (HFpEF). However, management of PH-HFpEF is challenging because mechanisms involved in the regulation of PH-HFpEF remain unclear. METHODS: We used a mass spectrometry-based comparative plasma proteomics approach as a sensitive and comprehensive hypothesis-generating discovery technique to profile proteins in patients with PH-HFpEF and control subjects. We then validated and investigated the role of one of the identified proteins using in vitro cell cultures, in vivo animal models, and independent cohort of human samples. RESULTS: Plasma proteomics identified high protein abundance levels of B2M (ß2-microglobulin) in patients with PH-HFpEF. Interestingly, both circulating and skeletal muscle levels of B2M were increased in mice with skeletal muscle SIRT3 (sirtuin-3) deficiency or high-fat diet-induced PH-HFpEF. Plasma and muscle biopsies from a validation cohort of PH-HFpEF patients were found to have increased B2M levels, which positively correlated with disease severity, especially pulmonary capillary wedge pressure and right atrial pressure at rest. Not only did the administration of exogenous B2M promote migration/proliferation in pulmonary arterial vascular endothelial cells but it also increased PCNA (proliferating cell nuclear antigen) expression and cell proliferation in pulmonary arterial vascular smooth muscle cells. Finally, B2m deletion improved glucose intolerance, reduced pulmonary vascular remodeling, lowered PH, and attenuated RV hypertrophy in mice with high-fat diet-induced PH-HFpEF. CONCLUSIONS: Patients with PH-HFpEF display higher circulating and skeletal muscle expression levels of B2M, the magnitude of which correlates with disease severity. Our findings also reveal a previously unknown pathogenic role of B2M in the regulation of pulmonary vascular proliferative remodeling and PH-HFpEF. These data suggest that circulating and skeletal muscle B2M can be promising targets for the management of PH-HFpEF.

Investigating the "sex paradox" in pulmonary arterial hypertension: Results from the Pulmonary Hypertension Association Registry (PHAR).

BACKGROUND: Female sex is a significant risk factor for pulmonary arterial hypertension (PAH), yet males with PAH have worse survival - a phenomenon referred to as the "sex paradox" in PAH. METHODS: All adult PAH patients in the Pulmonary Hypertension Association Registry (PHAR) with congruent sex and gender were included. Baseline differences in demographics, hemodynamics, functional parameters, and quality of life were assessed by sex. Kaplan-Meier survival analysis was used to evaluate survival by sex. Mediation analysis was conducted with Cox proportional hazards regression by comparing the unadjusted hazard ratios for sex before and after adjustment for covariates. The plausibility of collider-stratification bias was assessed by modeling how large an unmeasured factor would have to be to generate the observed sex-based mortality differences. Subgroup analysis was performed on idiopathic and incident patients. RESULTS: Among the 1,891 patients included, 75% were female. Compared to men, women had less favorable hemodynamics, lower 6-minute walk distance, more PAH therapies, and worse functional class; however, sex-based differences were less pronounced when accounting for body surface area or expected variability by gender. On multivariate analysis, women had a 48% lower risk of death compared to men (Hazard Ratio 0.52, 95% Confidence interval 0.36 - 0.74, p < 0.001). Modeling found that under reasonable assumptions collider-stratification could account for sex-based differences in mortality. CONCLUSIONS: In this large registry of PAH patients new to a care center, men had worse survival than women despite having more favorable baseline characteristics. Collider-stratification bias could account for the observed greater mortality among men.

Gender Disparities in Critical Care Procedure Training of Internal Medicine Residents.

Background: Procedural training is a required competency in internal medicine (IM) residency, yet limited data exist on residents' experience of procedural training. Objectives: We sought to understand how gender impacts access to procedural training among IM residents. Methods: A mixed-methods, explanatory sequential study was performed. Procedure volume for IM residents between 2016 and 2020 was assessed at two large academic residencies (Program A and Program B: 399 residents and 4,020 procedures). Procedural rates and actual versus expected procedure volume by gender were compared, with separate analyses by clinical environment (intensive care unit [ICU] or structured procedural service). Semistructured gender-congruent focus groups were conducted. Topics included identity formation as a proceduralist and the resident procedural learning experience, including perceived gender bias in procedure allocation. Results: Compared with men, women residents performed disproportionately fewer ICU procedures per month at Program A (1.4 vs. 2.7; P < 0.05) but not at Program B (0.36 vs. 0.54; P = 0.23). At Program A, women performed only 47% of ICU procedures, significantly fewer than the 54% they were expected to perform on the basis of their time on ICU rotations (P < 0.001). For equal gender distribution of procedural volume at Program A, 11% of the procedures performed by men would have needed to have been performed by women instead. Gender was not associated with differences in the Program A structured procedural service (53% observed vs. 52% expected; P = 0.935), Program B structured procedural service (40% observed vs. 43% expected; P = 0.174), or in Program B ICUs (33% observed vs. 34% expected; P = 0.656). Focus group analysis identified that women from both residencies perceived that assertiveness was required for procedural training in unstructured learning environments. Residents felt that gender influenced access to procedural opportunities, ability to self-advocate for procedural experience, identity formation as a proceduralist, and confidence in acquiring procedural skills. Conclusion: Gender disparities in access to procedural training during ICU rotations were seen at one institution but not another. There were ubiquitous perceptions that assertiveness was important to access procedural opportunities. We hypothesize that structured allocation of procedures would mitigate disparities by allowing all residents to access procedural training regardless of self-advocacy. Residency programs should adopt structured procedural training programs to counteract inequities.

Echocardiographic estimation of pulmonary vascular resistance in advanced lung disease.

Noninvasive assessment of pulmonary hemodynamics is often performed by echocardiographic estimation of the pulmonary artery systolic pressure (ePASP), despite limitations in the advanced lung disease population. Other noninvasive hemodynamic variables, such as echocardiographic pulmonary vascular resistance (ePVR), have not been studied in this population. We performed a retrospective analysis of 147 advanced lung disease patients who received both echocardiography and right heart catheterization for lung transplant evaluation. The ePVR was estimated by four previously described equations. Noninvasive and invasive hemodynamic parameters were compared in terms of correlation, agreement, and accuracy. The ePVR models strongly correlated with invasively determined PVR and had good accuracy with biases of <1 Wood units (WU), although with moderate precision and wide 95% limits of agreement varying from 5.9 to 7.8 Wood units. The ePVR models were accurate to within 1.9 WU in over 75% of patients. In comparison to the ePASP, ePVR models performed similarly in terms of correlation, accuracy, and precision when estimating invasive hemodynamics. In screening for pulmonary hypertension, ePVR models had equivalent testing characteristics to the ePASP. Mid-systolic notching of the right ventricular outflow tract Doppler signal identified a subgroup of 11 patients (7%) with significantly elevated PVR and mean pulmonary artery pressures without relying on the acquisition of a tricuspid regurgitation signal. Analysis of ePVR and determination of the notching pattern of the right ventricular outflow tract Doppler flow velocity envelope provide reliable insights into hemodynamics in advanced lung disease patients, although limitations in precision exist.

Sex Differences and Similarities in Valvular Heart Disease.

As populations age worldwide, the burden of valvular heart disease has grown exponentially, and so has the proportion of affected women. Although rheumatic valve disease is declining in high-income countries, degenerative age-related causes are rising. Calcific aortic stenosis and degenerative mitral regurgitation affect a significant proportion of elderly women, particularly those with comorbidities. Women with valvular heart disease have been underrepresented in many of the landmark studies which form the basis for guideline recommendations. As a consequence, surgical referrals in women have often been delayed, with worse postoperative outcomes compared with men. As described in this review, a more recent effort to include women in research studies and clinical trials has increased our knowledge about sex-based differences in epidemiology, pathophysiology, diagnostic criteria, treatment options, outcomes, and prognosis.

Inotropic therapies in heart failure and cardiogenic shock: an educational review.

Reduced systolic function is central to the pathophysiology and clinical sequelae of acute decompensated heart failure (ADHF) with reduced ejection fraction and cardiogenic shock. These clinical entities are the final common pathway for marked deterioration of right or left ventricular function and can occur in multiple clinical presentations including severe ADHF, myocardial infarction, post-cardiac surgery, severe pulmonary hypertension, and advanced or end-stage chronic heart failure. Inotropic therapies improve ventricular systolic function and may be divided into three classes on the basis of their mechanism of action (calcitropes, mitotropes, and myotropes). Most currently available therapies for cardiogenic shock are calcitropes which can provide critical haemodynamic support, but also may increase myocardial oxygen demand, ischaemia, arrhythmia, and mortality. Emerging therapies to improve cardiac function such as mitotropes (e.g. perhexiline, SGLT2i) or myotropes (e.g. omecamtiv mecarbil) may provide useful alternatives in the future.

Placental Abruption as a Risk Factor for Heart Failure.

Complications of pregnancy present an opportunity to identify women at high risk of cardiovascular disease (CVD). Placental abruption is a severe and understudied pregnancy complication, and its relationship with CVD is poorly understood. The California Healthcare Cost and Utilization Project database was used to identify women with hospitalized pregnancies in California between 2005 and 2009, with follow-up through 2011. Pregnancies, exposures, covariates, and outcomes were defined by International Classification of Diseases Ninth Revision codes. Cox proportional-hazards regression was used to examine the association between placental abruption and myocardial infarction (MI), stroke, and heart failure (HF). Multivariate models controlling for age, race, medical co-morbidities, pregnancy complications, psychiatric and substance use disorders, and socioeconomic factors were employed. Among over 1.5 million pregnancies, placental abruption occurred in 14,881 women (1%). Median follow-up time from delivery to event or censoring was 4.87 (interquartile range 3.54 to 5.96) years. In unadjusted models, placental abruption was associated with risk of HF, but not MI or stroke. In fully-adjusted models, placental abruption remained significantly associated with HF (Hazard ratio 1.44; 95% confidence interval 1.09 to 1.90). Among women with placental abruptions, hypertensive disorders of pregnancy and preterm birth respectively modified and mediated the association between placental abruption and HF. In conclusion, placental abruption is a risk factor for HF, particularly in women who also experience hypertensive disorders of pregnancy and preterm birth. Placental abruption is a specific adverse pregnancy outcome associated with risk of HF.

Age-related differences in hemodynamics and functional status in pulmonary arterial hypertension: Baseline results from the Pulmonary Hypertension Association Registry.

BACKGROUND: The age of patients with pulmonary arterial hypertension (PAH) has increased, with registries now reporting mean ages of 50 to 65 years old. Limited data exist on age-related differences in hemodynamic and functional assessments in PAH. METHODS: Adults with PAH in the Pulmonary Hypertension Association Registry were divided into 3 groups (18-50, 51-65, and >65 years old). Analysis of variance and chi-square testing were used to assess for baseline differences. Linear regression was used to examine the association of age with continuous hemodynamic and functional variables. RESULTS: A total of 769 patients with mean age of 56 ± 16 years were included. Older patients had more connective tissue disease-associated PAH and less drug-associated PAH. In linear regression models, each year of increased age was associated with shorter 6-minute walk distance (-3.37 meters; 95% CI, -3.97 to -2.76), lower mean pulmonary arterial pressure (-0.21 mm Hg; 95% CI, -0.27 to -0.15), and lower pulmonary vascular resistance (-0.06 Wood units; 95% CI, -0.09 to -0.04). Pulmonary arterial compliance, cardiac index, right ventricular stroke work index, and percent predicted 6-minute walk distance were unrelated to age; resistance-compliance time was negatively related to age (-3 milliseconds per year; 95% CI, -4 to -2). CONCLUSIONS: Relative to their pulmonary vascular resistance, older patients have lower pulmonary artery compliance and worse right ventricular performance. Based on these findings, we suspect that age influences right ventricular loading conditions and the response of the right ventricle to increased afterload.

Successful Use of Pulmonary Vasodilators in Acute Chest Syndrome Complicated by Persistent Right Ventricular Failure.

Pulmonary hypertension (PH) is a known consequence of sickle cell disease (SCD) and is associated with increased mortality and more frequent episodes of acute chest syndrome (ACS). Pulmonary pressures are known to increase during ACS, and right ventricular (RV) failure has been described as a significant cause of mortality in this condition. Management of ACS includes exchange transfusion, pain control, and prevention of hypovolemia and hypoxemia. However, in patients with a history of precapillary PH in whom ACS is complicated by persistent RV failure and cardiogenic shock, RV afterload reduction with pulmonary vasodilators may be an effective treatment strategy. Here, we present a case of a young man with SCD-associated PH and ACS who was successfully managed with inhaled and oral pulmonary vasodilators in the setting of persistent elevations in pulmonary vascular resistance leading to acute RV failure and cardiogenic shock.

Noninvasive estimation of pulmonary vascular resistance improves portopulmonary hypertension screening in liver transplant candidates.

Despite limitations in sensitivity and specificity, estimation of the pulmonary artery systolic pressure (ePASP) on echocardiography is used for portopulmonary hypertension (PoPH) screening in liver transplant (LT) candidates. We proposed that alternative echocardiographic models, such as estimated pulmonary vascular resistance (ePVR), may provide improved testing characteristics in PoPH screening. In a retrospective analysis of 100 LT candidates, we found that the formula ePVR = ePASP/VTIRVOT  + 3 if MSN (VTIRVOT  = right ventricular outflow tract time velocity integral; MSN = mid-systolic notching of the VTIRVOT Doppler signal) significantly improves accuracy of PoPH screening compared to ePASP. We determined the optimal ePVR cutoff for PoPH screening to be 2.76 Wood units, as this cutoff provided 100% sensitivity and 73% specificity in screening for clinically significant PoPH. Comparatively, ePASP at a cutoff of 40 mm Hg provided 91% sensitivity and 48% specificity. We devised a new screening algorithm based on the use of ePVR at intermediate ePASP values (35-54 mm Hg), and we confirmed the testing characteristics of this algorithm in a separate validation cohort of 50 LT candidates. In screening LT candidates for PoPH, the ePASP lacks accuracy, leading to unnecessary RHCs and undiagnosed cases of PoPH. A screening algorithm which incorporates the ePVR may be more reliable.

Amygdala selectively modulates defensive responses evoked from the superior colliculus in non-human primates.

Brain circuitry underlying defensive behaviors includes forebrain modulatory sites, e.g. the amygdala and hypothalamus, and midbrain effector regions, such as the deep/intermediate layers of the superior colliculus (DLSC). When disinhibited, this network biases behavior towards reflexive defense reactions. While well characterized in rodent models, little is known about this system in the primate brain. Employing focal pharmacological manipulations, we have previously shown that activation of the DLSC triggers reflexive defensive responses, including cowering, escape behaviors and defensive vocalizations. Here, we show that activation of the DLSC also disrupts normal dyadic social interactions between familiar pairs of monkeys. When the basolateral complex of the amygdala (BLA) was inhibited concurrent with DLSC activation, cowering behavior was attenuated, whereas escape behaviors and defensive vocalizations were not. Moreover, inhibition of the BLA, previously shown to produce a profound increase in dyadic social interactions, was unable to normalize the decrease in social behavior resulting from DLSC activation. Together these data provide an understanding of forebrain-midbrain interactions in a species and circuit with translational relevance for the psychiatry of anxiety and post-traumatic stress disorders.

Memory loss in a nonnavigational spatial task after hippocampal inactivation in monkeys.

The hippocampus has a well-documented role for spatial navigation across species, but its role for spatial memory in nonnavigational tasks is uncertain. In particular, when monkeys are tested in tasks that do not require navigation, spatial memory seems unaffected by lesions of the hippocampus. However, the interpretation of these results is compromised by long-term compensatory adaptation occurring in the days and weeks after lesions. To test the hypothesis that hippocampus is necessary for nonnavigational spatial memory, we selected a technique that avoids long-term compensatory adaptation. We transiently disrupted hippocampal function acutely at the time of testing by microinfusion of the glutamate receptor antagonist kynurenate. Animals were tested on a self-ordered spatial memory task, the Hamilton Search Task. In the task, animals are presented with an array of eight boxes, each containing a food reinforcer; one box may be opened per trial, with trials separated by a delay. Only the spatial location of the boxes serves as a cue to solve the task. The optimal strategy is to open each box once without returning to previously visited locations. Transient inactivation of hippocampus reduced performance to chance levels in a delay-dependent manner. In contrast, no deficits were seen when boxes were marked with nonspatial cues (color). These results clearly document a role for hippocampus in nonnavigational spatial memory in macaques and demonstrate the efficacy of pharmacological inactivation of this structure in this species. Our data bring the role of the hippocampus in monkeys into alignment with the broader framework of hippocampal function.

Defense-like behaviors evoked by pharmacological disinhibition of the superior colliculus in the primate.

Stimulation of the intermediate and deep layers of superior colliculus (DLSC) in rodents evokes both orienting/pursuit (approach) and avoidance/flight (defense) responses (Dean et al., 1989). These two classes of response are subserved by distinct output projections associated with lateral (approach) and medial (defense) DLSC (Comoli et al., 2012). In non-human primates, DLSC has been examined only with respect to orienting/approach behaviors, especially eye movements, and defense-like behaviors have not been reported. Here we examined the profile of behavioral responses evoked by activation of DLSC by unilateral intracerebral infusions of the GABA(A) receptor antagonist, bicuculline methiodide (BIC), in nine freely moving macaques. Across animals, the most consistently evoked behavior was cowering (all animals), followed by increased vocalization and escape-like behaviors (seven animals), and attack of objects (three animals). The effects of BIC were dose-dependent within the range 2.5-14 nmol (threshold dose of 4.6 nmol). The behaviors and their latencies to onset did not vary across different infusion sites within DLSC. Cowering and escape-like behaviors resembled the defense-like responses reported after DLSC stimulation in rats, but in the macaques these responses were evoked from both medial and lateral sites within DLSC. Our findings are unexpected in the context of an earlier theoretical perspective (Dean et al., 1989) that emphasized a preferential role of the primate DLSC for approach rather than defensive responses. Our data provide the first evidence for induction of defense-like behaviors by activation of DLSC in monkeys, suggesting that the role of DLSC in responding to threats is conserved across species.

Superior colliculus mediates cervical dystonia evoked by inhibition of the substantia nigra pars reticulata.

Cervical dystonia (CD; spasmodic torticollis) can be evoked by inhibition of substantia nigra pars reticulata (SNpr) in the nonhuman primate (Burbaud et al., 1998; Dybdal et al., 2012). Suppression of GABAergic neurons that project from SNpr results in the disinhibition of the targets to which these neurons project. It therefore should be possible to prevent CD by inhibition of the appropriate nigral target region(s). Here we tested the hypothesis that the deep and intermediate layers of the superior colliculus (DLSC), a key target of nigral projections, are required for the emergence of CD. To test this hypothesis, we pretreated the DLSC of four macaques with the GABA(A) agonist muscimol to determine whether this treatment would prevent CD evoked by muscimol infusions in SNpr. Our data supported this hypothesis: inhibition of DLSC attenuated CD evoked by muscimol in SNpr in all four animals. In two of the four subjects, quadrupedal rotations were evoked by muscimol application into SNpr sites that were distinct from those that induced dystonia. We found that inhibition of DLSC did not significantly alter quadrupedal rotations, suggesting that this response is dissociable from the SNpr-evoked CD. Our results are the first to demonstrate a role of DLSC in mediating the expression of CD. Furthermore, these data reveal a functional relationship between SNpr and DLSC in regulating posture and movement in the nonhuman primate, raising the possibility that the nigrotectal pathway has potential as a target for therapeutic interventions for CD.

Transient inactivation of orbitofrontal cortex blocks reinforcer devaluation in macaques.

The orbitofrontal cortex (OFC) and its interactions with the basolateral amygdala (BLA) are critical for goal-directed behavior, especially for adapting to changes in reward value. Here we used a reinforcer devaluation paradigm to investigate the contribution of OFC to this behavior in four macaques. Subjects that had formed associations between objects and two different primary reinforcers (foods) were presented with choices of objects overlying the two different foods. When one of the two foods was devalued by selective satiation, the subjects shifted their choices toward the objects that represented the nonsated food reward (devaluation effect). Transient inactivation of OFC by infusions of the GABA(A) receptor agonist muscimol into area 13 blocked the devaluation effect: the monkeys did not reduce their selection of objects associated with the devalued food. This effect was observed when OFC was inactivated during both satiation and the choice test, and during the choice test only. This supports our hypothesis that OFC activity is required during the postsatiety object choice period to guide the selection of objects. This finding sharply contrasts with the role of BLA in the same devaluation process (Wellman et al., 2005). Whereas activity in BLA was required during the selective satiation procedure, it was not necessary for guiding the subsequent object choice. Our results are the first to demonstrate that transient inactivation of OFC is sufficient to disrupt the devaluation effect, and to document a role for OFC distinct from that of BLA for the conditioned reinforcer devaluation process in monkeys.