Multi-omic and multispecies analysis of right ventricular dysfunction

BACKGROUND

Right ventricular failure (RVF) is a leading cause of morbidity and mortality in multiple cardiovascular diseases, but there are no treatments for RVF as therapeutic targets are not clearly defined. Contemporary transcriptomic/proteomic evaluations of RVF are predominately conducted in small animal studies, and data from large animal models are sparse. Moreover, a comparison of the molecular mediators of RVF across species is lacking.

METHODS

Transcriptomics and proteomics analyses defined the pathways associated with cardiac magnetic resonance imaging (MRI)-derived values of RV hypertrophy, dilation, and dysfunction in control and pulmonary artery banded (PAB) pigs. Publicly available data from rat monocrotaline-induced RVF and pulmonary arterial hypertension patients with preserved or impaired RV function were used to compare molecular responses across species.

RESULTS

PAB pigs displayed significant right ventricle/ventricular (RV) hypertrophy, dilation, and dysfunction as quantified by cardiac magnetic resonance imaging. Transcriptomic and proteomic analyses identified pathways associated with RV dysfunction and remodeling in PAB pigs. Surprisingly, disruptions in fatty acid oxidation (FAO) and electron transport chain (ETC) proteins were different across the 3 species. FAO and ETC proteins and transcripts were mostly downregulated in rats but were predominately upregulated in PAB pigs, which more closely matched the human response. All species exhibited similar dysregulation of the dilated cardiomyopathy and arrhythmogenic right ventricular cardiomyopathy pathways.

CONCLUSIONS

The porcine metabolic molecular signature was more similar to human RVF than rodents. These data suggest there may be divergent molecular responses of RVF across species, and pigs may more accurately recapitulate metabolic aspects of human RVF.

Ferroptosis Promotes Pulmonary Hypertension

Background

Mitochondrial dysfunction, characterized by impaired lipid metabolism and heightened reactive oxygen species (ROS) generation, results in lipid peroxidation-induced ferroptosis. Ferroptosis is an inflammatory mode of cell death as it both promotes complement activation and recruits macrophages. In pulmonary arterial hypertension (PAH), pulmonary arterial endothelial cells exhibit disrupted lipid metabolism and increased ROS production, and there is ectopic complement deposition and inflammatory macrophage accrual in the surrounding vasculature. However, the integrative effects of ferroptosis on metabolism, cellular landscape changes in the lung, complement induction, and pulmonary vascular remodeling are unknown.

Methods

Multi-omics analyses in rodents and a genetic association study in humans evaluated the role of ferroptosis in PAH.

Results

Ferrostatin-1, a small-molecule ferroptosis inhibitor, mitigated PAH severity and improved right ventricular function in monocrotaline rats. RNA-seq and proteomics analyses demonstrated ferroptosis was induced with increasingly severe PAH. Metabolomics and proteomics data showed ferroptosis inhibition restructured lung metabolism and altered phosphatidylcholine and phosphatidylethanolamine levels. RNA-seq, proteomics, and confocal microscopy revealed complement activation and pro-inflammatory cytokines/chemokines were suppressed by ferrostatin-1. Additionally, ferrostatin-1 combatted changes in endothelial, smooth muscle, and interstitial macrophage abundances and gene activation patterns in the lungs as revealed by deconvolution RNA-seq. Finally, the presence of six single-nucleotide polymorphisms in ferroptosis genes were independently associated with pulmonary hypertension severity in the Vanderbilt BioVU repository.

Conclusions

Rodent and human data nominate ferroptosis as a PAH regulating pathway via its ability to modulate lung lipid metabolism, repress pathogenic complement activation, dampen interstitial macrophage infiltration, and restore the lung cellular environment.

Ketone bodies in right ventricular failure: A unique therapeutic opportunity

Background

Ketone bodies are pleotropic metabolites that play important roles in multiple biological processes ranging from bioenergetics to inflammation regulation via suppression of the NLRP3 inflammasome, and epigenetic modifications. Ketone bodies are elevated in left ventricular failure (LVF) and multiple approaches that increase ketone concentrations exert advantageous cardiac effects in rodents and humans. However, the relationships between ketone bodies and right ventricular failure (RVF) are relatively unexplored.

Methods

51 PAH patients were dichotomized into preserved or impaired RV function based on a cardiac index of 2.2 L/min/m2. Impaired RV function patients were further segmented into intermediate or severe RV dysfunction based on a right atrial pressure of 8 mm Hg. Serum ketone bodies acetoacetate (AcAc) and beta-hydroxybutyrate (βOHB) were quantified using ultra performance liquid chromatography and mass spectrometry. In rodent studies, male Sprague Dawley rats were assigned to three groups: control (saline injection), monocrotaline (MCT) standard chow diet (MCT-Standard), and MCT ketogenic diet (MCT-Keto). Immunoblots and confocal microscopy probed macrophage NLRP3 activation in RV extracts and sections. RV fibrosis was determined by Picrosirus Red. Echocardiography evaluated RV function. Pulmonary arteriole remodeling was assessed from histological specimens.

Results

Human RVF patients lacked a compensatory ketosis as serum AcAc and βOHB levels were not associated with hemodynamic, echocardiographic, or biochemical measures of RV dysfunction. In rodent studies, AcAc and βOHB levels were also not elevated in MCT-mediated RVF, but the ketogenic diet significantly increased AcAc and βOHB levels. MCT-Keto exhibited suppressed NLRP3 activation with a reduction in NLRP3, ASC (apoptosis-associated speck-like protein), pro-caspase-1, and interleukin-1 beta on immunoblots. Moreover, the number of ASC-positive macrophage in RV sections was reduced, RV fibrosis was blunted, and RV function was augmented in MCT-Keto rats.

Conclusion

The ketogenic response is blunted in pulmonary arterial hypertension (PAH) patients with RVF. In the MCT rat model of PAH-mediated RVF, a dietary-induced ketosis improves RV function, suppresses NLRP3 inflammasome activation, and combats RV fibrosis. The summation of these data suggest ketogenic therapies may be particularly efficacious in RVF, and therefore future studies evaluating ketogenic interventions in human RVF are warranted.

Sex differences in right ventricular function between Groups 1 and 3 pulmonary hypertension

Group 3 pulmonary hypertension (PH) patients have disproportionate right ventricular dysfunction (RVD) compared to pulmonary arterial hypertension. We evaluated how sex and PH etiology modulated RVD. Strain echocardiography showed no intrasex differences between PH types. Heightened RVD in Group 3 PH may be due to a greater male proportion.

Effect of Combination of Balloon Pulmonary Angioplasty and Medical Therapy on Reverse Right Ventricular Remodeling and Hemodynamics in Chronic Thromboembolic Pulmonary Hypertension

INTRODUCTION

Chronic thromboembolic pulmonary hypertension (CTEPH) is a progressive and debilitating disorder that results from incomplete resolution of vascular obstructions resulting in pulmonary hypertension. Surgical pulmonary thromboendarterectomy (PTE) is the treatment of choice for CTEPH. Unfortunately, many CTEPH patients are ineligible for PTE or do not have access to an expert surgical center. Medical therapy imparts important symptomatic and exercise benefits for CTEPH patients, but it does not extend survival. Balloon pulmonary angioplasty (BPA) is an emerging transcatheter approach that is both safe and efficacious. However, the potential synergy between upfront BPA and medical therapy treatment approaches in patients with inoperable CTEPH is unknown. Here, we evaluated how the combination of BPA and medical therapy compared to medical therapy alone in a newly established BPA program.

METHODS

Twenty-one patients with inoperable or residual CTEPH were evaluated in this single-center observational study. Ten patients underwent upfront BPA and medical therapy while 11 patients were treated with medical therapy alone. Hemodynamic and echocardiographic assessments were performed at baseline and at least 1 month after completion of therapy. Continuous variables were compared using t-test or Mann-Whitney U-test. Categorical variables were analyzed with Chi squared and Fisher's exact test where appropriate.

RESULTS

Combination therapy significantly reduced mean pulmonary arterial pressure (mPAP) and pulmonary vascular resistance (PVR), but medical therapy only significantly lowered PVR. Comprehensive echocardiographic analysis revealed a more robust reverse right ventricular (RV) remodeling effect and augmentation of RV function with combination therapy. At the end of study, the combination therapy group had lower mPAP and PVR and better RV function. Importantly, there were no significant adverse effects in patients treated with BPA.

CONCLUSION

Combination therapy significantly improves hemodynamics and RV function in inoperable CTEPH while carrying an acceptable risk profile, even in a newly developed program. Further studies comparing upfront combination therapy to medical therapy with larger, long-term, and randomized approaches should be considered.

Effect of Chronic Digoxin Use on Mortality and Heart Failure Hospitalization in Pulmonary Arterial Hypertension

Background Digoxin acutely increases cardiac output in patients with pulmonary arterial hypertension (PAH) and right ventricular failure; however, the effects of chronic digoxin use in PAH are unclear. Methods and Results Data from the Minnesota Pulmonary Hypertension Repository were used. The primary analysis used likelihood of digoxin prescription. The primary end point was a composite of all-cause mortality or heart failure (HF) hospitalization. Secondary end points included all-cause mortality, HF hospitalization, and transplant-free survival. Multivariable Cox proportional hazards analyses determined the hazard ratios (HR) and 95% CIs for the primary and secondary end points. Among 205 patients with PAH in the repository, 32.7% (n=67) were on digoxin. Digoxin was more often prescribed to patients with severe PAH and right ventricular failure. After propensity score-matching, 49 patients were digoxin users, and 70 patients were nonusers; of these 31 (63.3%) in the digoxin group and 41 (58.6%) in nondigoxin group met the primary end point during a median follow-up time of 2.1 (0.6-5.0) years. Digoxin users had a higher combined all-cause mortality or HF hospitalization (HR, 1.82 [95% CI, 1.11-2.99]), all-cause mortality (HR, 1.92 [95% CI, 1.06-3.49]), HF hospitalization (HR, 1.89 [95% CI, 1.07-3.35]), and worse transplant-free survival (HR, 2.00 [95% CI, 1.12-3.58]) even after adjusting for patient characteristics and severity of PAH and right ventricular failure. Conclusions In this retrospective, nonrandomized cohort, digoxin treatment was associated with greater all-cause mortality and HF hospitalization, even after multivariate correction. Future randomized controlled trials should assess the safety and efficacy of chronic digoxin use in PAH.

Pulmonary Arterial Hypertension Patients Have a Proinflammatory Gut Microbiome and Altered Circulating Microbial Metabolites

Rationale: Inflammation drives pulmonary arterial hypertension (PAH). Gut dysbiosis causes immune dysregulation and systemic inflammation by altering circulating microbial metabolites; however, little is known about gut dysbiosis and microbial metabolites in PAH. Objectives: To characterize the gut microbiome and microbial metabolites in patients with PAH. Methods: We performed 16S ribosomal RNA gene and shotgun metagenomics sequencing on stool from patients with PAH, family control subjects, and healthy control subjects. We measured markers of inflammation, gut permeability, and microbial metabolites in plasma from patients with PAH, family control subjects, and healthy control subjects. Measurements and Main Results: The gut microbiome was less diverse in patients with PAH. Shannon diversity index correlated with measures of pulmonary vascular disease but not with right ventricular function. Patients with PAH had a distinct gut microbial signature at the phylogenetic level, with fewer copies of gut microbial genes that produce antiinflammatory short-chain fatty acids (SCFAs) and secondary bile acids and lower relative abundances of species encoding these genes. Consistent with the gut microbial changes, patients with PAH had relatively lower plasma concentrations of SCFAs and secondary bile acids. Patients with PAH also had enrichment of species with the microbial genes that encoded the proinflammatory microbial metabolite trimethylamine. The changes in the gut microbiome and circulating microbial metabolites between patients with PAH and family control subjects were not as substantial as the differences between patients with PAH and healthy control subjects. Conclusions: Patients with PAH have proinflammatory gut dysbiosis, in which lower circulating SCFAs and secondary bile acids may facilitate pulmonary vascular disease. These findings support investigating modulation of the gut microbiome as a potential treatment for PAH.

A Multi-omic and Multi-Species Analysis of Right Ventricular Failure

Right ventricular failure (RVF) is a leading cause of morbidity and mortality in multiple cardiovascular diseases, but there are no approved treatments for RVF as therapeutic targets are not clearly defined. Contemporary transcriptomic/proteomic evaluations of RVF are predominately conducted in small animal studies, and data from large animal models are sparse. Moreover, a comparison of the molecular mediators of RVF across species is lacking. Here, we used transcriptomics and proteomics analyses to define the molecular pathways associated with cardiac MRI-derived values of RV hypertrophy, dilation, and dysfunction in pulmonary artery banded (PAB) piglets. Publicly available data from rat monocrotaline-induced RVF and pulmonary arterial hypertension patients with preserved or impaired RV function were used to compare the three species. Transcriptomic and proteomic analyses identified multiple pathways that were associated with RV dysfunction and remodeling in PAB pigs. Surprisingly, disruptions in fatty acid oxidation (FAO) and electron transport chain (ETC) proteins were different across the three species. FAO and ETC proteins and transcripts were mostly downregulated in rats, but were predominately upregulated in PAB pigs, which more closely matched the human data. Thus, the pig PAB metabolic molecular signature was more similar to human RVF than rodents. These data suggest there may be divergent molecular responses of RVF across species, and that pigs more accurately recapitulate the metabolic aspects of human RVF.

Junctophilin-2 Regulates Mitochondrial Metabolism

Right ventricular dysfunction (RVD) is a risk factor for mortality in multiple cardiovascular diseases, but approaches to combat RVD are lacking. Therapies used for left heart failure are largely ineffective in RVD, and thus the identification of molecules that augment RV function could improve outcomes in a wide-array of cardiac limitations. Junctophilin-2 (JPH2) is an essential protein that plays important roles in cardiomyocytes, including calcium handling/maintenance of t-tubule structure and gene transcription. Additionally, JPH2 may regulate mitochondrial function as Jph2 knockout mice exhibit cardiomyocyte mitochondrial swelling and cristae derangements. Moreover, JPH2 knockdown in embryonic stem cell-derived cardiomyocytes induces downregulation of the mitochondrial protein mitofusin-2 (MFN2), which disrupts mitochondrial cristae structure and transmembrane potential. Impaired mitochondrial metabolism drives RVD, and here we evaluated the mitochondrial role of JPH2. We showed JPH2 directly interacts with MFN2, ablation of JPH2 suppresses mitochondrial biogenesis, oxidative capacity, and impairs lipid handling in iPSC-CM. Gene therapy with AAV9-JPH2 corrects RV mitochondrial morphological defects, mitochondrial fatty acid metabolism enzyme regulation, and restores the RV lipidomic signature in the monocrotaline rat model of RVD. Finally, AAV-JPH2 improves RV function without altering PAH severity, showing JPH2 provides an inotropic effect to the dysfunction RV.

An integrated proteomic and transcriptomic signature of the failing right ventricle in monocrotaline induced pulmonary arterial hypertension in male rats

Aim: Pulmonary arterial hypertension (PAH) is an obstructive pulmonary vasculopathy that results in death from right ventricular failure (RVF). There is limited understanding of the molecular mechanisms of RVF in PAH. Methods: In a PAH-RVF model induced by injection of adult male rats with monocrotaline (MCT; 60 mg/kg), we performed mass spectrometry to identify proteins that change in the RV as a consequence of PAH induced RVF. Bioinformatic analysis was used to integrate our previously published RNA sequencing data from an independent cohort of PAH rats. Results: We identified 1,277 differentially regulated proteins in the RV of MCT rats compared to controls. Integration of MCT RV transcriptome and proteome data sets identified 410 targets that are concordantly regulated at the mRNA and protein levels. Functional analysis of these data revealed enriched functions, including mitochondrial metabolism, cellular respiration, and purine metabolism. We also prioritized 15 highly enriched protein:transcript pairs and confirmed their biological plausibility as contributors to RVF. We demonstrated an overlap of these differentially expressed pairs with data published by independent investigators using multiple PAH models, including the male SU5416-hypoxia model and several male rat strains. Conclusion: Multiomic integration provides a novel view of the molecular phenotype of RVF in PAH which includes dysregulation of pathways involving purine metabolism, mitochondrial function, inflammation, and fibrosis.

Association of Right Ventricular Afterload With Atrial Fibrillation Risk in Older Adults: The Atherosclerosis Risk in Communities Study

BACKGROUND

Atrial fibrillation (AF) is widely perceived to originate from the left atrium (LA). Whether increases in right ventricular (RV) afterload in older adults play an etiological role in AF genesis independent of LA and left ventricular (LV) remodeling is unknown.

RESEARCH QUESTION

Is higher RV afterload associated with greater AF risk independent of LA and LV remodeling?

STUDY DESIGN AND METHODS

In this observational prospective study, we included 2,246 community-dwelling older adults (mean age, 75 years) without known cardiovascular disease, with LV ejection fraction > 50%, LA volume index < 34 mL/m2, and E/e' ratio < 14 and a measurable functional tricuspid regurgitation jet velocity. From 2D-echocardiograms, we estimated pulmonary artery systolic pressure (PASP) and pulmonary vascular resistance (PVR). We ascertained incident AF (through 2018) from hospital discharge codes and death certificates. We estimated hazard ratios (HR) by Cox regression.

RESULTS

During follow-up (median, 6.3 years; interquartile interval, 5.5-6.9 years), 215 participants developed AF. AF risk was significantly higher in the third (vs first) tertile of PASP (HR, 1.65; 95% CI, 1.08-2.54) and PVR (HR, 1.38; 95% CI, 1.00-2.08) independent of LA and LV structure and function, heart rate, BMI, prevalent sleep apnea, systemic BP, antihypertensive medications, and lung, kidney, and thyroid function. These associations persisted after further exclusion of participants with tricuspid regurgitation jet velocity > 2.8 m/s and lateral and septal mitral annular velocity above age- and sex-specific reference limits.

INTERPRETATION

In older adults, higher RV afterload is associated with greater AF risk independent of LA and LV remodeling. Future research should focus on confirming this novel association and elucidate underlying mechanisms.

Glyoxylase-1 combats dicarbonyl stress and right ventricular dysfunction in rodent pulmonary arterial hypertension

Background

Heightened glycolytic flux is associated with right ventricular (RV) dysfunction in pulmonary arterial hypertension (PAH). Methylglyoxal, a glycolysis byproduct, is a highly reactive dicarbonyl that has toxic effects via non-enzymatic post-translational modifications (protein glycation). Methylglyoxal is degraded by the glyoxylase system, which includes the rate-limiting enzyme glyoxylase-1 (GLO1), to combat dicarbonyl stress. However, the potential consequences of excess protein glycation on RV function are unknown.

Methods

Bioinformatics analysis of previously identified glycated proteins predicted how protein glycation regulated cardiac biology. Methylglyoxal treatment of H9c2 cardiomyocytes evaluated the consequences of excess protein glycation on mitochondrial respiration. The effects of adeno-associated virus serotype 9-mediated (AAV9) GLO1 expression on RV function in monocrotaline rats were quantified with echocardiography and hemodynamic studies. Immunoblots and immunofluorescence were implemented to probe the effects of AAV-Glo1 on total protein glycation and fatty acid oxidation (FAO) and fatty acid binding protein levels.

Results

In silico analyses highlighted multiple mitochondrial metabolic pathways may be affected by protein glycation. Exogenous methylglyoxal minimally altered mitochondrial respiration when cells metabolized glucose, however methylglyoxal depressed FAO. AAV9-Glo1 increased RV cardiomyocyte GLO1 expression, reduced total protein glycation, partially restored mitochondrial density, and decreased lipid accumulation. In addition, AAV9-Glo1 increased RV levels of FABP4, a fatty acid binding protein, and hydroxyacyl-CoA dehydrogenase trifunctional multienzyme complex subunits alpha and beta (HADHA and HADHB), the two subunits of the mitochondrial trifunctional protein for FAO. Finally, AAV9-Glo1 blunted RV fibrosis and improved RV systolic and diastolic function.

Conclusion

Excess protein glycation promotes RV dysfunction in preclinical PAH, potentially through suppression of FAO.

Incidence and Risk Factors of Pulmonary Hypertension After Venous Thromboembolism: An Analysis of a Large Health Care Database

Background

Pulmonary hypertension (PH) is a devastating potential complication of pulmonary embolism, a manifestation of venous thromboembolism (VTE). The incidence of and risk factors for PH in those with prior VTE are poorly characterized.

Methods and Results

International Classification of Diseases ( ICD ) codes from inpatient and outpatient medical claims from MarketScan administrative databases for years 2011 to 2018 were used to identify cases of VTE, comorbidities before the VTE event, and PH occurring subsequent to the VTE event. Cumulative incidence and hazard ratios (HR), and their 95% CI, were calculated. The 170 021 VTE cases included in the analysis were on average (±SD) 57.5±15.8 years old and 50.5% were female. A total of 5943 PH cases accrued over an average follow‐up of 1.94 years. Two years after incident VTE, the cumulative incidence (95% CI) of PH was 3.5% (3.4%–3.7%) overall. It was higher among older individuals, among women (3.9% [3.8%–4.1%]) than men (3.2% [3.0%–3.3%]), and among patients presenting with pulmonary embolism (6.2% [6.0%–6.5%]) than those presenting with deep vein thrombosis only (1.1% [1.0%–1.2%]). Adjusting for age and sex, risk of PH was higher among patients with VTE with underlying comorbidities. Using the Charlson comorbidity index, there was a dose–response relationship, whereby greater scores were associated with increased PH risk (score ≥5 versus 0: HR, (2.50 [2.30–2.71])). When evaluating individual comorbidities, the strongest associations were observed with concomitant heart failure (HR, 2.17 [2.04–2.31]), chronic pulmonary disease (2.01 [1.90–2.14]), and alcohol abuse (1.66 [1.29–2.13]).

Conclusions

In this large, real‐world population of insured people with VTE, 3.5% developed PH in the 2 years following their initial VTE event. Risk was higher among women, with increasing age, and in those with additional comorbidities at the time of the VTE event. These data provide insights into the burden of PH and risk factors for PH among patients with VTE.

Macrophage-NLRP3 Activation Promotes Right Ventricle Failure in Pulmonary Arterial Hypertension

RATIONALE

Pulmonary arterial hypertension (PAH) often results in death from right ventricular failure (RVF). NLRP3-macrophage activation may promote RVF in PAH.

OBJECTIVES

Evaluating the contribution of the NLRP3 inflammasome in RV-macrophages to PAH-RVF.

METHODS

Rats with decompensated RV hypertrophy (RVH) [monocrotaline (MCT) and Sugen-5416 hypoxia (SuHx)] were compared with compensated RVH rats [pulmonary artery banding (PAB)]. Echocardiography and right heart catheterization were performed. Macrophages, atrial natriuretic peptide (ANP) and fibrosis were evaluated by microscopy or flow cytometry. NLRP3 inflammasome activation and cardiotoxicity were confirmed by immunoblot and in vitro strategies. MCT-rats were treated with SC-144 (a GP130 antagonist) and MCC950 (an NLRP3 inhibitor). Macrophage-NLRP3 activity was evaluated in PAH-RVF patients.

MEASUREMENTS AND MAIN RESULTS

Macrophages, fibrosis, and ANP were increased in MCT and SuHx-RVs but not LVs or PAB rats. While MCT-RV macrophages were inflammatory, lung macrophages were anti-inflammatory. CCR2+ macrophages (monocyte-derived) were increased in MCT- and SuHx-RVs and highly expressed NLRP3. The macrophage-NLRP3 pathway was upregulated in PAH patients' decompensated RVs. Cultured MCT-monocytes showed NLRP3 activation, and in co-culture experiments resulted in cardiomyocyte mitochondrial damage, which MCC950 prevented. In vivo, MCC950 reduced NLRP3 activation and regressed pulmonary vascular disease and RVF. SC-144 reduced RV-macrophages and NLRP3 content, prevented STAT3 activation, and improved RV function without regressing pulmonary vascular disease.

CONCLUSION

NLRP3-macrophage activation occurs in the decompensated RV in preclinical PAH models and PAH patients. Inhibiting GP130 or NLRP3 signaling improves RV function. The concept that PAH-RVF results from RV inflammation rather than solely from elevated RV afterload suggest a new therapeutic paradigm. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Inflammatory Glycoprotein 130 Signaling Links Changes in Microtubules and Junctophilin-2 to Altered Mitochondrial Metabolism and Right Ventricular Contractility

BACKGROUND

Right ventricular dysfunction (RVD) is the leading cause of death in pulmonary arterial hypertension (PAH), but no RV-specific therapy exists. We showed microtubule-mediated junctophilin-2 dysregulation (MT-JPH2 pathway) causes t-tubule disruption and RVD in rodent PAH, but the druggable regulators of this critical pathway are unknown. GP130 (glycoprotein 130) activation induces cardiomyocyte microtubule remodeling in vitro; however, the effects of GP130 signaling on the MT-JPH2 pathway and RVD resulting from PAH are undefined.

METHODS

Immunoblots quantified protein abundance, quantitative proteomics defined RV microtubule-interacting proteins (MT-interactome), metabolomics evaluated the RV metabolic signature, and transmission electron microscopy assessed RV cardiomyocyte mitochondrial morphology in control, monocrotaline, and monocrotaline-SC-144 (GP130 antagonist) rats. Echocardiography and pressure-volume loops defined the effects of SC-144 on RV-pulmonary artery coupling in monocrotaline rats (8-16 rats per group). In 73 patients with PAH, the relationship between interleukin-6, a GP130 ligand, and RVD was evaluated.

RESULTS

SC-144 decreased GP130 activation, which normalized MT-JPH2 protein expression and t-tubule structure in the monocrotaline RV. Proteomics analysis revealed SC-144 restored RV MT-interactome regulation. Ingenuity pathway analysis of dysregulated MT-interacting proteins identified a link between microtubules and mitochondrial function. Specifically, SC-144 prevented dysregulation of electron transport chain, Krebs cycle, and the fatty acid oxidation pathway proteins. Metabolomics profiling suggested SC-144 reduced glycolytic dependence, glutaminolysis induction, and enhanced fatty acid metabolism. Transmission electron microscopy and immunoblots indicated increased mitochondrial fission in the monocrotaline RV, which SC-144 mitigated. GP130 antagonism reduced RV hypertrophy and fibrosis and augmented RV-pulmonary artery coupling without altering PAH severity. In patients with PAH, higher interleukin-6 levels were associated with more severe RVD (RV fractional area change 23±12% versus 30±10%, P=0.002).

CONCLUSIONS

GP130 antagonism reduces MT-JPH2 dysregulation, corrects metabolic derangements in the RV, and improves RVD in monocrotaline rats.

With No Lysine Kinase 1 Promotes Metabolic Derangements and RV Dysfunction in Pulmonary Arterial Hypertension

Small molecule inhibition of with no lysine kinase 1 (WNK1) (WNK463) signaling activates adenosine monophosphate-activated protein kinase signaling and mitigates membrane enrichment of glucose transporters 1 and 4, which decreases protein O-GlcNAcylation and glycation. Quantitative proteomics of right ventricular (RV) mitochondrial enrichments shows WNK463 prevents down-regulation of several mitochondrial metabolic enzymes. and metabolomics analysis suggests multiple metabolic processes are corrected. Physiologically, WNK463 augments RV systolic and diastolic function independent of pulmonary arterial hypertension severity. Hypochloremia, a condition of predicted WNK1 activation in patients with pulmonary arterial hypertension, is associated with more severe RV dysfunction. These results suggest WNK1 may be a druggable target to combat metabolic dysregulation and may improve RV function and survival in pulmonary arterial hypertension.

Intermittent Fasting Enhances Right Ventricular Function in Preclinical Pulmonary Arterial Hypertension

Background Intermittent fasting (IF) confers pleiotropic cardiovascular benefits including restructuring of the gut microbiome and augmentation of cellular metabolism. Pulmonary arterial hypertension (PAH) is a rare and lethal disease characterized by right ventricular (RV) mitochondrial dysfunction and resultant lipotoxicity and microbiome dysbiosis. However, the effects of IF on RV function in PAH are unexplored. Therefore, we investigated how IF altered gut microbiota composition, RV function, and survival in the monocrotaline model of PAH. Methods and Results Male Sprague Dawley rats were randomly allocated into 3 groups: control, monocrotaline-ad libitum feeding, and monocrotaline-IF (every other day feeding). Echocardiography and invasive hemodynamics showed IF improved RV systolic and diastolic function despite no significant change in PAH severity. IF prevented premature mortality (30% mortality rate in monocrotaline-ad libitum versus 0% in monocrotaline-IF rats, P=0.04). IF decreased RV cardiomyocyte hypertrophy and reduced RV fibrosis. IF prevented RV lipid accrual on Oil Red O staining and ceramide accumulation as determined by metabolomics. IF mitigated the reduction in jejunum villi length and goblet cell abundance when compared with monocrotaline-ad libitum. The 16S ribosomal RNA gene sequencing demonstrated IF changed the gut microbiome. In particular, there was increased abundance of Lactobacillus in monocrotaline-IF rats. Metabolomics profiling revealed IF decreased RV levels of microbiome metabolites including bile acids, aromatic amino acid metabolites, and gamma-glutamylated amino acids. Conclusions IF directly enhanced RV function and restructured the gut microbiome. These results suggest IF may be a non-pharmacological approach to combat RV dysfunction, a currently untreatable and lethal consequence of PAH.

Abstract 10736: Gut Dysbiosis and Altered Circulating Microbial Metabolites in Patients with Pulmonary Arterial Hypertension

Introduction: Inflammation plays a mechanistic role in pulmonary arterial hypertension (PAH); however, what triggers inflammation remains unclear.

Hypothesis: PAH is characterized by gut dysbiosis and barrier dysfunction, leading to an altered burden of circulating microbial metabolic products, promoting disease. We aimed to characterize the gut microbiome and circulating microbial metabolic products in healthy controls and PAH patients.

Methods: The V4 hypervariable region of the 16S rRNA gene was analyzed from fecal samples of 40 healthy controls and 57 PAH patients. Plasma was analyzed for interleukin (IL)-6, claudin-3, trimethylamine N-oxide (TMAO), short chain fatty acids, and secondary bile acids.

Results: PAH patients had elevated plasma IL-6 (Fig 1A, P =.02), claudin-3, a measure of intestinal permeability (Fig 1B, P =.04), and TMAO (Fig 1C, P =.04), and reduced taurolithocholic acid (Fig 1D, P =.02). Short chain fatty acid levels were not significantly different (data not shown). Principal component analysis (PCOA) of pairwise Bray-Curtis dissimilarity showed distinct microbiome compositions (Fig 1E, P <.001). The Shannon diversity index (Fig 1F, P <.001) and species richness (Fig 1G, P =0.005) were lower in PAH patients. Linear discriminant analysis (LDA) of effect size revealed that PAH patients had increased relative abundances of Bacteroidetes and Proteobacteria and decreased relative abundances of Ruminococcaceae and Lachnospiraceae (Fig 1H). There was no difference in gut microbiome richness and Shannon diversity between patients with low, intermediate, and high-risk REVEAL scores (data not shown).

Conclusions: PAH patients have distinct gut dysbiosis, increased intestinal permeability (claudin-3), and circulating microbial metabolic products. These findings support our hypothesis that microbiome-driven, pro-inflammatory signals may contribute to PAH pathogenesis.

Association of right ventricular dysfunction and pulmonary hypertension with adverse 30-day outcomes in COVID-19 patients

Background

Cardiac manifestations in COVID-19 are multifactorial and are associated with increased mortality. The clinical utility and prognostic value of echocardiography in COVID-19 inpatients is not clearly defined. We aim to identify echocardiographic parameters that are associated with 30-day clinical outcomes secondary to COVID-19 hospitalization.

Methods

This retrospective cohort study was conducted in a large tertiary hospital in New York City during the COVID-19 pandemic. It included 214 adult inpatients with a laboratory-confirmed diagnosis of COVID-19 by reverse transcriptase polymerase chain reaction assay (RT-PCR) for SARS-CoV-2 on nasopharyngeal swab and had a transthoracic echocardiogram performed during the index hospitalization. Primary outcome was 30-day all-cause inpatient mortality. Secondary outcomes were 30-day utilization of mechanical ventilator support, vasopressors, or renal replacement therapy.

Results

Mild right ventricular systolic dysfunction (odds ratio (OR): 3.51, 95% confidence interval (CI): 1.63–7.57, p = 0.001), moderate to severe right ventricular systolic dysfunction (OR: 7.30, 95% CI: 2.20–24.25, p = 0.001), pulmonary hypertension (OR: 5.39, 95% CI: 1.96–14.86, p = 0.001), and moderate to severe tricuspid regurgitation (OR: 3.92, 95% CI: 1.71–9.03, p = 0.001) were each associated with increased odds of 30-day all-cause inpatient mortality. Pulmonary hypertension and moderate to severe right ventricular dysfunction were each associated with increased odds of 30-day utilization of mechanical ventilator support and vasopressors.

Conclusions

Right ventricular dysfunction, pulmonary hypertension, and moderate to severe tricuspid regurgitation were associated with increased odds for 30-day inpatient mortality. This study highlights the importance of echocardiography and its clinical utility and prognostic value for evaluating hospitalized COVID-19 patients.

A Case Report of Portopulmonary Hypertension Precipitated by Transjugular Intrahepatic Portosystemic Shunt

We report here a case of portopulmonary hypertension following transjugular intrahepatic portosystemic shunt.

Hemodynamic Characteristics and Outcomes of Pulmonary Hypertension in Patients Undergoing Tricuspid Valve Repair or Replacement

BACKGROUND

The impact of pulmonary hypertension (PH) on outcomes after surgical tricuspid valve replacement (TVR) and repair (TVr) is unclear. We sought to characterize PH in patients undergoing TVR/TVr, based on invasive hemodynamics and evaluate the effect of PH on mortality.

METHODS

We identified 86 consecutive patients who underwent TVR/TVr with invasive hemodynamic measurements within 3 months before surgery. We used Kaplan-Meier survival and restricted mean survival time (RMST) analyses to quantify the effects of PH on survival.

RESULTS

The mean age was 63 ± 13 years, 59% were female, 45% had TVR, 55% had TVr, 39.5% had isolated TVR/TVr, and 60.5% had TVR/TVr concomitant with other cardiac surgeries). Eighty-six percent of these patients had PH with a mean pulmonary artery pressure of 30 ± 10 mm Hg, pulmonary vascular resistance (PVR) of 2.5 (interquartile range: 1.5-3.9) Wood units (WU), pulmonary arterial compliance of 2.3 (1.6-3.6) mL/mm Hg, and pulmonary arterial elastance of 0.8 (0.6-1.2) mm Hg/mL. Cardiac output was mildly reduced at 4.0 ± 1.4 L/min, with elevated right-atrial pressure (14 ± 12 mm Hg) and pulmonary capillary wedge pressure (19 ± 7 mm Hg). Over a median follow-up of 6.3 years, 22% of patients died. Patients with PVR ≥ 2.5 WU had lower RMST over 5 years compared with patients with PVR < 2.5 WU.

CONCLUSION

PH is common in patients undergoing TVR/TVr, with combined pre- and postcapillary being the most common type. PVR ≥ 2.5 WU is associated with lower survival at 5-year follow-up.

Sex Differences in Right Ventricular Dysfunction: Insights From the Bench to Bedside

There are inherent distinctions in right ventricular (RV) performance based on sex as females have better RV function than males. These differences are magnified and have very important prognostic implications in two RV-centric diseases, pulmonary hypertension (PH), and arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D). In both PH and ARVC/D, RV dysfunction results in poor patient outcomes. However, there are no currently approved therapies specifically targeting the failing RV, an important unmet need for these two life-threatening disorders. In this review, we highlight human data demonstrating divergent RV phenotypes in healthy, PH, and ARVC/D patients based on sex. Furthermore, we discuss the links between estrogen (the female predominant sex hormone), testosterone (the male predominant sex hormone), and dehydroepiandrosterone (a precursor hormone for multiple sex hormones in males and females) and RV function in both disorders. To provide potential mechanistic insights into sex differences in RV function, we review data that investigate how sex hormones combat or contribute to pathophysiological changes in the RV. Finally, we highlight the ongoing clinical trials in pulmonary arterial hypertension targeting estrogen and dehydroepiandrosterone signaling. Hopefully, a greater understanding of the factors that promote superior RV function in females will lead to novel therapeutic approaches to combat RV dysfunction in PH and ARVC/D.

Treatment Targets for Right Ventricular Dysfunction in Pulmonary Arterial Hypertension

Right ventricle (RV) dysfunction is the strongest predictor of mortality in pulmonary arterial hypertension (PAH), but, at present, there are no therapies directly targeting the failing RV. Although there are shared molecular mechanisms in both RV and left ventricle (LV) dysfunction, there are important differences between the 2 ventricles that may allow for the development of RV-enhancing or RV-directed therapies. In this review, we discuss the current understandings of the dysregulated pathways that promote RV dysfunction, highlight RV-enriched or RV-specific pathways that may be of particular therapeutic value, and summarize recent and ongoing clinical trials that are investigating RV function in PAH. It is hoped that development of RV-targeted therapies will improve quality of life and enhance survival for this deadly disease.

Excess Protein O-GlcNAcylation Links Metabolic Derangements to Right Ventricular Dysfunction in Pulmonary Arterial Hypertension

The hexosamine biosynthetic pathway (HBP) converts glucose to uridine-diphosphate-N-acetylglucosamine, which, when added to serines or threonines, modulates protein function through protein O-GlcNAcylation. Glutamine-fructose-6-phosphate amidotransferase (GFAT) regulates HBP flux, and AMP-kinase phosphorylation of GFAT blunts GFAT activity and O-GlcNAcylation. While numerous studies demonstrate increased right ventricle (RV) glucose uptake in pulmonary arterial hypertension (PAH), the relationship between O-GlcNAcylation and RV function in PAH is unexplored. Therefore, we examined how colchicine-mediated AMP-kinase activation altered HBP intermediates, O-GlcNAcylation, mitochondrial function, and RV function in pulmonary artery-banded (PAB) and monocrotaline (MCT) rats. AMPK activation induced GFAT phosphorylation and reduced HBP intermediates and O-GlcNAcylation in MCT but not PAB rats. Reduced O-GlcNAcylation partially restored the RV metabolic signature and improved RV function in MCT rats. Proteomics revealed elevated expression of O-GlcNAcylated mitochondrial proteins in MCT RVs, which fractionation studies corroborated. Seahorse micropolarimetry analysis of H9c2 cardiomyocytes demonstrated colchicine improved mitochondrial function and reduced O-GlcNAcylation. Presence of diabetes in PAH, a condition of excess O-GlcNAcylation, reduced RV contractility when compared to nondiabetics. Furthermore, there was an inverse relationship between RV contractility and HgbA1C. Finally, RV biopsy specimens from PAH patients displayed increased O-GlcNAcylation. Thus, excess O-GlcNAcylation may contribute to metabolic derangements and RV dysfunction in PAH.

Repurposing of medications for pulmonary arterial hypertension

This manuscript on drug repurposing incorporates the broad experience of members of the Pulmonary Vascular Research Institute's Innovative Drug Development Initiative as an open debate platform for academia, the pharmaceutical industry and regulatory experts surrounding the future design of clinical trials in pulmonary hypertension. Drug repurposing, use of a drug in a disease for which it was not originally developed, in pulmonary arterial hypertension has been a remarkable success story, as highlighted by positive large phase 3 clinical trials using epoprostenol, bosentan, iloprost, and sildenafil. Despite the availability of multiple therapies for pulmonary arterial hypertension, mortality rates have modestly changed. Moreover, pulmonary arterial hypertension patients are highly symptomatic and frequently end up on parental therapy and lung transplant waiting lists. Therefore, an unmet need for new treatments exists and drug repurposing may be an important avenue to address this problem.

The evolving role of interventional cardiology in the treatment of pulmonary hypertension

Pulmonary hypertension (PH) is a heterogeneous group of diseases defined by a mean pulmonary arterial pressure greater than 20 mmHg. Clinically, PH is classified into five groups and the group of PH generally defines the cause of PH and the therapeutic options. Currently, medical therapies that target the prostacyclin, endothelin, and nitric oxide pathways are used in pulmonary arterial hypertension and chronic thromboembolic PH (CTEPH) patients. Moreover, surgery can improve outcomes in PH as pulmonary thromboendarterectomy can be curative for CTEPH and lung transplantation is used for end-stage PH. Despite these diverse treatment options, PH patients continue to have high symptom burden and poor long-term outcomes. However, advances in percutaneous technology are opening new avenues for the management of PH. In this review, we discuss the available data supporting the use of four interventional procedures: balloon atrial septostomy, transcatheter Potts shunt, balloon pulmonary angioplasty, and pulmonary artery denervation for the treatment of PH. These procedures provide hemodynamic and functional improvements in PH patients, but they come with their own unique risk profiles. Hopefully, these procedures will continue to be refined and thereby provide a venue for interventional cardiology to safely and effectively improve outcomes for PH moving forward.

Hypochloremia Is a Noninvasive Predictor of Mortality in Pulmonary Arterial Hypertension

Background

Pulmonary arterial hypertension (PAH) is a lethal disease. In resource‐limited countries PAH outcomes are worse because therapy costs are prohibitive. To improve global outcomes, noninvasive and widely available biomarkers that identify high‐risk patients should be defined. Serum chloride is widely available and predicts mortality in left heart failure, but its prognostic utility in PAH requires further investigation.

Methods and Results

In this study 475 consecutive PAH patients evaluated at the University of Minnesota and Vanderbilt University PAH clinics were examined. Clinical characteristics were compared by tertiles of serum chloride. Both the Kaplan‐Meier method and Cox regression analysis were used to assess survival and predictors of mortality, respectively. Categorical net reclassification improvement and relative integrated discrimination improvement compared prediction models. PAH patients in the lowest serum chloride tertile (≤101 mmol/L: hypochloremia) had the lowest 6‐minute walk distance and highest right atrial pressure despite exhibiting no differences in pulmonary vascular disease severity. The 1‐, 3‐, and 5‐year survival was reduced in hypochloremic patients when compared with the middle‐ and highest‐tertile patients (86%/64%/44%, 95%/78%/59%, and, 91%/79%/66%). After adjustment for age, sex, diuretic use, serum sodium, bicarbonate, and creatinine, the hypochloremic patients had increased mortality when compared with the middle‐tertile and highest‐tertile patients. The Minnesota noninvasive model (functional class, 6‐minute walk distance, and hypochloremia) was as effective as the French noninvasive model (functional class, 6‐minute walk distance, and elevated brain natriuretic peptide or N‐terminal pro–brain natriuretic peptide) for predicting mortality.

Conclusions

Hypochloremia (≤101 mmol/L) identifies high‐risk PAH patients independent of serum sodium, renal function, and diuretic use.

Clinical Determinants and Prognostic Implications of Right Ventricular Dysfunction in Pulmonary Hypertension Caused by Chronic Lung Disease

Background

Patients with pulmonary hypertension caused by chronic lung disease (Group 3 PH) have disproportionate right ventricle (RV) dysfunction, but the correlates and clinical implications of RV dysfunction in Group 3 PH are not well defined.

Methods and Results

We performed a cohort study of 147 Group 3 PH patients evaluated at the University of Minnesota. RV systolic function was quantified using right ventricular fractional area change (RVFAC) and ⁺dP/dt_max/instantaneous pressure. Tau and RV diastolic stiffness characterized RV diastolic function. Multivariate linear regression was used to define correlates of RVFAC. Kaplan‐Meier and Cox proportional hazards analyses were used to examine freedom from heart failure hospitalization and death. Positive correlates of RVFAC on univariate analysis were pulmonary arterial compliance, cardiac index, and left ventricular diastolic dimension. Conversely, male sex, N‐terminal pro‐brain natriuretic peptide, heart rate, right atrial enlargement, mean pulmonary arterial pressure, and pulmonary vascular resistance were negative correlates. Male sex was the strongest predictor of lower RVFAC, after adjusting for pulmonary vascular resistance and pulmonary arterial compliance. When comparing sexes, males had lower RVFAC (26% versus 31%, P=0.03) both overall and for any given mean pulmonary arterial pressure and pulmonary vascular resistance value. Males exhibited a reduction in ⁺dP/dt_max/instantaneous pressure as pulmonary vascular resistance increased, whereas females did not. There were no sex differences in RV diastolic function. RV dysfunction (RVFAC <28%) was associated with increased risk of heart failure hospitalization or death (hazard ratio: 1.84, 95% CI: 1.04–3.10, P=0.035).

Conclusions

Male sex is associated with RV dysfunction in Group 3 PH, even after adjusting for RV afterload. RV dysfunction (RVFAC <28%) identifies Group 3 PH patients at risk for poor outcomes.

EXPRESS: Transition from Parental Prostacyclin to Selexipag: A Case Series of Five Pulmonary Arterial Hypertension Patients

Parental prostacyclin is the only therapy with a proven survival benefit in pulmonary arterial hypertension (PAH). However, some patients are unable to tolerate continuous prostacyclin infusion because of central line infection, side effects, or sociocultural factors. Selexipag is a recently approved prostacyclin receptor agonist that is able to blunt PAH disease progression. Although in the same molecular pathway, the interchangeability of selexipag with prostacyclin infusions is relatively unexplored. Here, we present a case series of five stable PAH patients who were functional class (FC) I or II that were transitioned from prostacyclin infusion to selexipag using a standardized protocol in the inpatient setting. We show that the transition to selexipag in five highly selected patients was tolerated with no significant changes in FC, minimal changes in pulmonary vascular disease severity, and no significant PAH-related complications. However, there was a trend for a reduction in cardiac index after transition to selexipag. These data suggest that a transition from prostacyclin infusion to selexipag can be achieved in clinically stable PAH patients who are unable to tolerate continuous prostacyclin infusion. However, this approach should only be selectively implemented at specialized centers with close follow-up due to the trend for a reduction in cardiac index after transition to selexipag.

Survival in pulmonary hypertension due to chronic lung disease: Influence of low diffusion capacity of the lungs for carbon monoxide

BACKGROUND

Patients with pulmonary hypertension (PH) due to chronic lung disease (Group 3 PH) have poor long-term outcomes. However, predictors of survival in Group 3 PH are not well described.

METHODS

We performed a cohort study of Group 3 PH patients (n = 143; mean age 65 ± 12 years, 52% female) evaluated at the University of Minnesota. The Kaplan-Meier method and Cox regression analysis were used to assess survival and predictors of mortality, respectively. The clinical characteristics and survival were compared in patients categorized by PH severity based on the World Health Organization (WHO) classification and lung disease etiology.

RESULTS

After a median follow-up of 1.4 years, there were 69 (48%) deaths. The 1-, 3-, and 5-year survival rates were 79%, 48%, and 31%. Age, coronary artery disease, atrial fibrillation, Charlson comorbidity index, serum N-terminal pro‒brain natriuretic peptide (NT-proBNP), creatinine, diffusion capacity of carbon monoxide (DLCO), total lung capacity, left ventricular ejection fraction, right atrial and right ventricular enlargement on echocardiography, cardiac index, and pulmonary vascular resistance (PVR) were univariate predictors of survival. On multivariable analysis, DLCO was the only predictor of mortality (adjusted hazard ratio [HR] for every 10% decrease in predicted value: 1.31 [95% confidence interval 1.12 to 1.47]; p = 0.003). The 1-/5-year survival by tertiles of DLCO was 84%/56%, 82%/44%, and 63%/14% (p = 0.01), respectively. On receiver-operating characteristic curve analysis, DLCO <32% of predicted had the highest sensitivity and specificity for predicting survival. The 1- and 5-year survival in patients with a DLCO ≥32% predicted was 84% and 60% vs 68% and 13% in patients with a DLCO <32% predicted (adjusted HR: 2.5 [95% confidence interval 1.3 to 5.0]; p = 0.007). Lung volumes and DLCO were not related, but higher PVR was strongly associated with reduced DLCO. There was increased mortality in interstitial lung disease‒PH as compared with chronic obstructive pulmonary disease‒PH, but PH severity based on the WHO classification did not alter survival.

CONCLUSIONS

Low DLCO is a predictor of mortality and should be used to risk-stratify Group 3 PH patients.

Exacerbation of dystrophic cardiomyopathy by phospholamban deficiency mediated chronically increased cardiac Ca2+ cycling in vivo

Cardiomyopathy is a significant contributor to morbidity and mortality in Duchenne muscular dystrophy (DMD). Membrane instability, leading to intracellular Ca²⁺ mishandling and overload, causes myocyte death and subsequent fibrosis in DMD cardiomyopathy. On a cellular level, cardiac myocytes from mdx mice have dysregulated Ca²⁺ handling, including increased resting Ca²⁺ and slow Ca²⁺ decay, especially evident under stress conditions. Sarco(endo)plasmic reticulum Ca²⁺ ATPase and its regulatory protein phospholamban (PLN) are potential therapeutic targets for DMD cardiomyopathy owing to their key role in regulating intracellular Ca²⁺ cycling. We tested the hypothesis that enhanced cardiac Ca²⁺ cycling would remediate cardiomyopathy caused by dystrophin deficiency. We used a genetic complementation model approach by crossing dystrophin-deficient mdx mice with PLN knockout (PLNKO) mice [termed double-knockout (DKO) mice]. As expected, adult cardiac myocytes isolated from DKO mice exhibited increased contractility and faster relaxation associated with increased Ca²⁺ transient peak height and faster Ca²⁺ decay rate compared with control mice. However, compared with wild-type, mdx, and PLNKO mice, DKO mice unexpectedly had reduced in vivo systolic and diastolic function as measured by echocardiography. Furthermore, Evans blue dye uptake was increased in DKO hearts compared with control, mdx, and PLNKO hearts, demonstrating increased membrane damage, which subsequently led to increased fibrosis in the DKO myocardium in vivo. In conclusion, despite enhanced intracellular Ca²⁺ handling at the myocyte level, DMD cardiomyopathy was exacerbated owing to unregulated chronic increases in Ca²⁺ cycling in DKO mice in vivo. These findings have potentially important implications for ongoing therapeutic strategies for the dystrophic heart. NEW & NOTEWORTHY This study examined the effects of phospholamban ablation on the pathophysiology of cardiomyopathy in dystrophin-deficient mice. In this setting, contractility and Ca²⁺ cycling were enhanced in isolated myocytes; however, in vivo heart function was diminished. Additionally, sarcolemmal integrity was compromised and fibrosis was increased. This is the first study, to our knowledge, examining unregulated Ca²⁺ cycling in the dystrophin-deficient heart. Results from this study have implications for potential therapies targeting Ca²⁺ handling in dystrophic cardiomyopathy. Listen to this article's corresponding podcast at https://ajpheart.podbean.com/e/unregulated-ca2-cycling-exacerbates-dmd-cardiomyopathy/ .

Colchicine Depolymerizes Microtubules, Increases Junctophilin-2, and Improves Right Ventricular Function in Experimental Pulmonary Arterial Hypertension

BACKGROUND

Pulmonary arterial hypertension (PAH) is a lethal disease characterized by obstructive pulmonary vascular remodeling and right ventricular (RV) dysfunction. Although RV function predicts outcomes in PAH, mechanisms of RV dysfunction are poorly understood, and RV-targeted therapies are lacking. We hypothesized that in PAH, abnormal microtubular structure in RV cardiomyocytes impairs RV function by reducing junctophilin-2 (JPH2) expression, resulting in t-tubule derangements. Conversely, we assessed whether colchicine, a microtubule-depolymerizing agent, could increase JPH2 expression and enhance RV function in monocrotaline-induced PAH.

METHODS AND RESULTS

Immunoblots, confocal microscopy, echocardiography, cardiac catheterization, and treadmill testing were used to examine colchicine's (0.5 mg/kg 3 times/week) effects on pulmonary hemodynamics, RV function, and functional capacity. Rats were treated with saline (n=28) or colchicine (n=24) for 3 weeks, beginning 1 week after monocrotaline (60 mg/kg, subcutaneous). In the monocrotaline RV, but not the left ventricle, microtubule density is increased, and JPH2 expression is reduced, with loss of t-tubule localization and t-tubule disarray. Colchicine reduces microtubule density, increases JPH2 expression, and improves t-tubule morphology in RV cardiomyocytes. Colchicine therapy diminishes RV hypertrophy, improves RV function, and enhances RV-pulmonary artery coupling. Colchicine reduces small pulmonary arteriolar thickness and improves pulmonary hemodynamics. Finally, colchicine increases exercise capacity.

CONCLUSIONS

Monocrotaline-induced PAH causes RV-specific derangement of microtubules marked by reduction in JPH2 and t-tubule disarray. Colchicine reduces microtubule density, increases JPH2 expression, and improves both t-tubule architecture and RV function. Colchicine also reduces adverse pulmonary vascular remodeling. These results provide biological plausibility for a clinical trial to repurpose colchicine as a RV-directed therapy for PAH.

Chronic use of PAH-specific therapy in World Health Organization Group III Pulmonary Hypertension: a systematic review and meta-analysis

Pulmonary hypertension (PH) complicating chronic obstructive pulmonary disease (COPD-PH) and interstitial lung disease (ILD-PH) (World Health Organization [WHO] Group III PH) increases medical costs and reduces survival. Despite limited data, many clinicians are using pulmonary arterial hypertension (PAH)-specific therapy to treat WHO Group III PH patients. To further investigate the utility of PAH-specific therapy in WHO Group III PH, we performed a systematic review and meta-analysis. Relevant studies from January 2000 through May 2016 were identified in the MEDLINE, EMBASE, and COCHRANE electronic databases and www.clinicaltrials.gov. Change in six-minute walk distance (6MWD) was estimated using random effects meta-analysis techniques. Five randomized controlled trials (RCTs) in COPD-PH (128 placebo or standard treatment and 129 PAH-medication treated patients), two RCTs in ILD-PH (23 placebo and 46 treated patients), and four single-arm clinical trials (50 patients) in ILD-PH were identified. Treatment in both COPD-PH and ILD-PH did not worsen hypoxemia. Symptomatic burden was not consistently reduced but there were trends for reduced pulmonary artery pressures and pulmonary vascular resistance with PAH-specific therapy. As compared to placebo, 6MWD was not significantly improved with PAH-specific therapy in the five COPD-PH RCTs (42.7 m; 95% confidence interval [CI], –1.0 – 86.3). In the four single-arm studies in ILD-PH patients, there was a significant improvement in 6MWD after PAH-specific treatment (46.2 m; 95% CI, 27.9–64.4), but in the two ILD-PH RCTs there was not an improvement (21.6 m; 95% CI, –17.8 – 61.0) in exercise capacity when compared to placebo. Due to the small numbers of patients evaluated and inconsistent beneficial effects, the utility of PAH-specific therapy in WHO Group III PH remains unproven. A future clinical trial that is appropriately powered is needed to definitively determine the efficacy of this widely implemented treatment approach.

World Health Organization Group I Pulmonary Hypertension: Epidemiology and Pathophysiology

Pulmonary arterial hypertension (PAH) is a debilitating disease characterized by pathologic remodeling of the resistance pulmonary arteries, ultimately leading to right ventricular (RV) failure and death. In this article we discuss the definition of PAH, the initial epidemiology based on the National Institutes of Health Registry, and the updated epidemiology gleaned from contemporary registries, pathogenesis of pulmonary vascular dysfunction and proliferation, and RV failure in PAH.

Pulmonary pulse wave transit time is associated with right ventricular-pulmonary artery coupling in pulmonary arterial hypertension

Pulmonary pulse wave transit time (pPTT), defined as the time for the systolic pressure pulse wave to travel from the pulmonary valve to the pulmonary veins, has been reported to be reduced in pulmonary arterial hypertension (PAH); however, the underlying mechanism of reduced pPTT is unknown. Here, we investigate the hypothesis that abbreviated pPTT in PAH results from impaired right ventricular-pulmonary artery (RV-PA) coupling. We quantified pPTT using pulsed-wave Doppler ultrasound from 10 healthy age- and sex-matched controls and 36 patients with PAH. pPTT was reduced in patients with PAH compared with controls. Univariate analysis revealed the following significant predictors of reduced pPTT: age, right ventricular fractional area change (RV FAC), tricuspid annular plane excursion (TAPSE), pulmonary arterial pressures (PAP), diastolic pulmonary gradient, transpulmonary gradient, pulmonary vascular resistance, and RV-PA coupling (defined as RV FAC/mean PAP or TAPSE/mean PAP). Although the correlations between pPTT and invasive markers of pulmonary vascular disease were modest, RV FAC (r = 0.64, P < 0.0001), TAPSE (r = 0.67, P < 0.0001), and RV-PA coupling (RV FAC/mean PAP: r = 0.72, P < 0.0001; TAPSE/mean PAP: r = 0.74, P < 0.0001) had the strongest relationships with pPTT. On multivariable analysis, only RV FAC, TAPSE, and RV-PA coupling were independent predictors of pPTT. We conclude that shortening of pPTT in patients with PAH results from altered RV-PA coupling, probably occurring as a result of reduced pulmonary arterial compliance. Thus, pPTT allows noninvasive determination of the status of both the pulmonary vasculature and the response of the RV in patients with PAH, thereby allowing monitoring of disease progression and regression.

Effects of Beta-Blocker Withdrawal in Acute Decompensated Heart Failure: A Systematic Review and Meta-Analysis

OBJECTIVES

This study sought to evaluate the effects of beta-blocker withdrawal in acute decompensated heart failure (ADHF).

BACKGROUND

Published reports showed trends for either no harm or increased risk of in-hospital mortality, short-term mortality, and rehospitalization rates in patients admitted for ADHF that discontinued beta-blockers; however, a comprehensive analysis has not been conducted.

METHODS

Relevant studies from January 2000 through January 2015 were identified in the PubMed, EMBASE, and COCHRANE electronic databases. Where appropriate data were available, weighted relative risks were estimated using random-effects meta-analysis techniques.

RESULTS

Five observational studies and 1 randomized clinical trial (n = 2,704 patients who continued beta-blocker therapy and n = 439 patients who discontinued beta-blocker therapy) that reported the short-term effects of beta-blocker withdrawal in ADHF were included in the analyses. In 2 studies, beta-blocker withdrawal significantly increased risk of in-hospital mortality (risk ratio: 3.72; 95% confidence interval [CI]: 1.51 to 9.14). Short-term mortality (relative risk: 1.61; 95% CI: 1.04 to 2.49; 4 studies) and combined short-term rehospitalization or death (relative risk: 1.59; 95% CI: 1.03 to 2.45; 4 studies) were also significantly increased.

CONCLUSIONS

Discontinuation of beta-blockers in patients admitted with ADHF was associated with significantly increased in-hospital mortality, short-term mortality, and the combined endpoint of short-term rehospitalization or mortality. These data suggest beta-blockers should be continued in ADHF patients if their clinical picture allows.

Cardiorenal Syndrome Type 1: Renal Dysfunction in Acute Decompensated Heart Failure

OBJECTIVE

To present a review of cardiorenal syndrome type 1 (CRS1).

METHODS

Review of the literature.

RESULTS

Acute kidney injury occurs in approximately one-third of patients with acute decompensated heart failure (ADHF) and the resultant condition was named CRS1. A growing body of literature shows CRS1 patients are at high risk for poor outcomes, and thus there is an urgent need to understand the pathophysiology and subsequently develop effective treatments. In this review we discuss prevalence, proposed pathophysiology including hemodynamic and nonhemodynamic factors, prognosticating variables, data for different treatment strategies, and ongoing clinical trials and highlight questions and problems physicians will face moving forward with this common and challenging condition.

CONCLUSION

Further research is needed to understand the pathophysiology of this complex clinical entity and to develop effective treatments.