Deep phenotyping of unaffected carriers of pathogenic BMPR2 variants screened for pulmonary arterial hypertension.

INTRODUCTION: Pathogenic variants in the gene encoding for BMPR2 are a major genetic risk factor for heritable pulmonary arterial hypertension (PAH). Due to incomplete penetrance, deep-phenotyping of unaffected carriers (UCs) of a pathogenic BMPR2 variant through multi-modality screening may aid in early diagnosis and identify susceptibility traits for future development of PAH. METHODS: 28 UCs (44±16 years, 57% female) and 21 healthy controls (43±18 years, 48% female) underwent annual screening, including cardiac magnetic resonance imaging (cMRI), transthoracic echocardiography (TTE), cardiopulmonary exercise testing (CPET) and right heart catheterization (RHC). Right ventricular (RV) pressure-volume (PV) loops were constructed to assess load independent contractility and compared with a healthy control group. A transgenic Bmpr2Δ71Ex1/+ rat model was employed to validate findings in humans. RESULTS: UCs had lower indexed right ventricular end-diastolic (80±18 mL·m-2 versus 64±14 mL·m-2;p= 0.003), end-systolic (34±11 mL·m-2 versus 27±8 mL·m-2;p=0.024) and left end-diastolic volumes (69±14 mL·m-2 versus 60±11 mL·m-2;p=0.019) than control subjects. Bmpr2Δ71Ex1/+ rats were also observed to have smaller cardiac volumes than WT rats. PV loop analysis showed significantly higher afterload (Ea) (0.15±0.06 versus 0.27±0.08; p<0.001), and end-systolic elastance (Ees) 0.28±0.07 versus 0.35±0.10; p=0.047) in addition to lower RV-pulmonary artery coupling (Ees/Ea)(2.24±1.03 versus 1.36±0.37; p=0.006) in UCs. During the 4-year follow-up period, two UCs developed PAH with normal NT-proBNP and TTE indices at diagnosis. CONCLUSION: Unaffected BMPR2 mutation carriers have an altered cardiac phenotype mimicked in Bmpr2Δ71Ex1/+ transgenic rats. Future efforts in establishing an effective screening protocol for individuals at risk for developing PAH warrants longer follow-up periods.

Right ventricular diastolic adaptation to pressure overload in different rat strains.

Different rat strains are used in various animal models of pulmonary hypertension and right ventricular (RV) failure. No systematic assessment has been made to test differences in RV response to pressure overload between rat strains. We compared RV adaptation to pulmonary trunk banding (PTB) in Wistar (W), Sprague Dawley (SD), and Fischer344 (F) rats by hemodynamic profiling focusing on diastolic function. Age-matched male rat weanlings were randomized to sham surgery (W-sham, n = 5; SD-sham, n = 4; F-sham, n = 4) or PTB (W-PTB, n = 8; SD-PTB, n = 8; F-PTB, n = 8). RV function was evaluated after 5 weeks by echocardiography, cardiac MRI, and invasive pressure-volume measurements. PTB caused RV failure and increased RV systolic pressures four-fold in all three PTB groups compared with sham. W- and SD-PTB had a 2.4-fold increase in RV end-systolic volume index compared with sham, while F-PTB rats were less affected. Diastolic and right atrial impairment were evident by increased RV end-diastolic elastance, filling pressure, and E/e' in PTB rats compared with sham, again F-PTB the least affected. In conclusions, PTB caused RV failure with signs of diastolic dysfunction. Despite a similar increase in RV systolic pressure, F-PTB rats showed less RV dilatation and a more preserved diastolic function compared with W- and SD-PTB.

Evaluating the technical use of a Fitbit during an intervention for patients with pulmonary arterial hypertension with quality of life as primary endpoint: Lessons learned from the UPHILL study.

This article examines technical use of Fitbit during an intervention for pulmonary hypertension (PAH)-patients. Technical issues with the device led to data being unavailable(37.5%). During intervention objective daily physical activity (DPA) decreased and subjective DPA increased. This emphasizes that an assessment of DPA in PAH requires incorporating both objective and subjective measurements.

Pneumonectomy combined with SU5416 or monocrotaline pyrrole does not cause severe pulmonary hypertension in mice.

In the field of pulmonary hypertension (PH), a well-established protocol to induce severe angioproliferation in rats (SuHx) involves combining the VEGF-R inhibitor Sugen 5416 (SU5416) with three weeks of hypoxia (Hx). Additionally, injecting monocrotaline (MCT) into rats can induce inflammation and shear stress in the pulmonary vasculature, leading to neointima-like remodeling. However, the SuHx protocol in mice is still controversial, with some studies suggesting it yields higher and reversible PH than Hx alone, possibly due to species-dependent hypoxic responses. To establish an alternative rodent model of PH, we hypothesized mice would be more sensitive to hemodynamic changes secondary to shear stress compared to Hx. We attempted to induce severe and irreversible PH in mice by combining SU5416 or monocrotaline pyrrole (MCTP) injection with pneumonectomy (PNx). However, our experiments showed SU5416 administered to mice at various time points after PNx did not result in severe PH. Similarly, mice injected with MCTP after PNx (MPNx) showed no difference in right ventricular systolic pressure or exacerbated pulmonary vascular remodeling compared to PNx alone. These findings collectively demonstrate that C57/B6 mice do not develop severe and persistent PH when PNx is combined with either SU5416 or MCTP.

Mechanical stimulation of induced pluripotent stem derived cardiac fibroblasts.

Cardiac fibrosis contributes to the development of heart failure, and is the response of cardiac fibroblasts (CFs) to pressure or volume overload. Limiting factors in CFs research are the poor availability of human cells and the tendency of CFs to transdifferentiate into myofibroblasts when cultured in vitro. The possibility to generate CFs from induced pluripotent stem cells (iPSC), providing a nearly unlimited cell source, opens new possibilities. However, the behaviour of iPSC-CFs under mechanical stimulation has not been studied yet. Our study aimed to assess the behaviour of iPSC-CFs under mechanical stretch and pro-fibrotic conditions. First, we confirm that iPSC-CFs are comparable to primary CFs at gene, protein and functional level. Furthermore, iPSC-derived CFs adopt a pro-fibrotic response to transforming growth factor beta (TGF-ß). In addition, mechanical stretch inhibits TGF-ß-induced fibroblast activation in iPSC-CFs. Thus, the responsiveness to cytokines and mechanical stimulation of iPSC-CFs demonstrates they possess key characteristics of primary CFs and may be useful for disease modelling.

Tricuspid regurgitation in pulmonary arterial hypertension: a right ventricular volumetric and functional analysis.

BACKGROUND: The consequences of tricuspid regurgitation (TR) for right ventricular (RV) function and prognosis in pulmonary arterial hypertension (PAH) are poorly described and effects of tricuspid valve repair on the RV are difficult to predict. METHODS: In 92 PAH patients with available cardiac magnetic resonance (CMR) studies, TR volume was calculated as the difference between RV stroke volume and forward stroke volume, i.e. pulmonary artery (PA) stroke volume. Survival was estimated from the time of the CMR scan to cardiopulmonary death or lung transplantation. In a subgroup, pressure-volume loop analysis including two-parallel elastances was applied to evaluate effective elastances, including net afterload (effective arterial elastance (E a)), forward afterload (effective pulmonary arterial elastance (E pa)) and backward afterload (effective tricuspid regurgitant elastance (E TR)). The effects of tricuspid valve repair were simulated using the online software package Harvi. RESULTS: 26% of PAH patients had a TR volume ≥30 mL. Greater TR volume was associated with increased N-terminal pro-brain natriuretic peptide (p=0.018), mean right atrial pressure (p<0.001) and RV end-systolic and -diastolic volume (both p<0.001). TR volume ≥30 mL was associated with a poor event-free survival (p=0.008). In comparison to E a, E pa correlated better with indices of RV dysfunction. Lower end-systolic elastance (E es) (p=0.002) and E TR (p=0.030), higher E pa (p=0.001) and reduced E es/E pa (p<0.001) were found in patients with a greater TR volume. Simulations predicted that tricuspid valve repair increases RV myocardial oxygen consumption in PAH patients with severe TR and low E es unless aggressive volume reduction is accomplished. CONCLUSIONS: In PAH, TR has prognostic significance and is associated with low RV contractility and RV-PA uncoupling. However, haemodynamic simulations showed detrimental consequences of tricuspid valve repair in PAH patients with low RV contractility.

Clinical Correlates of a Nonplexiform Vasculopathy in Patients With a Diagnosis of Idiopathic Pulmonary Arterial Hypertension.

BACKGROUND: The clinical phenotype of patients with idiopathic pulmonary arterial hypertension (IPAH) has changed. Whether subgroups of patients with IPAH have different vascular phenotypes is a subject of debate. RESEARCH QUESTION: What are the histologic patterns and their clinical correlates in patients with a diagnosis of IPAH or hereditary pulmonary arterial hypertension? STUDY DESIGN AND METHODS: In this this cross-sectional registry study, lung histology of 50 patients with IPAH was assessed qualitatively by two experienced pathologists. In addition, quantitative analysis by means of histopathologic morphometry using immunohistochemistry was performed. Histopathologic characteristics were correlated with clinical and hemodynamic parameters. RESULTS: In this cohort of 50 patients with IPAH, a plexiform vasculopathy was observed in 26 of 50 patients (52%), whereas 24 of 50 patients (48%) showed a nonplexiform vasculopathy. The nonplexiform vasculopathy was characterized by prominent pulmonary microvascular (arterioles and venules) remodeling and vascular rarefaction. Although hemodynamic parameters were comparable in plexiform vs nonplexiform vasculopathy, patients with nonplexiform vasculopathy were older, more often were male, more often had a history of cigarette smoking, and had lower diffusing capacity of the lungs for carbon monoxide at diagnosis. No mutations in established pulmonary arterial hypertension genes were found in the nonplexiform group. INTERPRETATION: This study revealed different vascular phenotypes within the current spectrum of patients with a diagnosis of IPAH, separated by clinical characteristics (age, sex, history of cigarette smoking, and diffusing capacity of the lungs for carbon monoxide at diagnosis). Potential differences in underlying pathobiological mechanisms between patients with plexiform and nonplexiform microvascular disease should be taken into account in future research strategies unravelling the pathophysiologic features of pulmonary hypertension and developing biology-targeted treatment approaches.

Embedding routine health care data in clinical trials: with great power comes great responsibility.

Randomised clinical trials (RCTs) are vital for medical progress. Unfortunately, 'traditional' RCTs are expensive and inherently slow. Moreover, their generalisability has been questioned. There is considerable overlap in routine health care data (RHCD) and trial-specific data. Therefore, integration of RHCD in an RCT has great potential, as it would reduce the effort and costs required to collect data, thereby overcoming some of the major downsides of a traditional RCT. However, use of RHCD comes with other challenges, such as privacy issues, as well as technical and practical barriers. Here, we give a current overview of related initiatives on national cardiovascular registries (Netherlands Heart Registration, Heart4Data), showcasing the interrelationships between and the relevance of the different registries for the practicing physician. We then discuss the benefits and limitations of RHCD use in the setting of a pragmatic RCT from a cardiovascular perspective, illustrated by a case study in heart failure.

Toward the Implementation of Optimal Cardiac Magnetic Resonance Risk Stratification in Pulmonary Arterial Hypertension.

BACKGROUND: The 2022 European Society of Cardiology/European Respiratory Society pulmonary hypertension (PH) guidelines incorporate cardiac magnetic resonance (CMR) imaging metrics in the risk stratification of patients with pulmonary arterial hypertension (PAH). Thresholds to identify patients at estimated 1-year mortality risks of < 5%, 5% to 20%, and > 20% are introduced. However, these cutoff values are mostly single center-based and require external validation. RESEARCH QUESTION: What are the discriminative prognostic properties of the current CMR risk thresholds stratifying patients with PAH? STUDY DESIGN AND METHODS: We analyzed data from incident, treatment-naïve patients with PAH from the Amsterdam University Medical Centres, Vrije Universiteit, The Netherlands. The discriminative properties of the proposed CMR three risk strata were tested at baseline and first reassessment, using the following PH guideline variables: right ventricular ejection fraction, indexed right ventricular end-systolic volume, and indexed left ventricular stroke volume. RESULTS: A total of 258 patients with PAH diagnosed between 2001 and 2022 fulfilled the study criteria and were included in this study. Of these, 172 had follow-up CMR imaging after 3 months to 1.5 years. According to the CMR three risk strata, most patients were classified at intermediate risk (n = 115 [45%]) upon diagnosis. Only 29 (11%) of patients with PAH were classified at low risk, and 114 (44%) were classified at high risk. Poor survival discrimination was seen between risk groups. Appropriate survival discrimination was seen at first reassessment. INTERPRETATION: Risk stratifying patients with PAH with the recent proposed CMR cutoffs from the European Society of Cardiology/European Respiratory Society 2022 PH guidelines requires adjustment because post-processing consensus is lacking and general applicability is limited. Risk assessment at follow-up yielded better survival discrimination, emphasizing the importance of the individual treatment response.

Long-term effects of pulmonary endarterectomy on pulmonary hemodynamics, cardiac function, and exercise capacity in chronic thromboembolic pulmonary hypertension.

BACKGROUND: Long-term changes in exercise capacity and cardiopulmonary hemodynamics after pulmonary endarterectomy (PEA) for chronic thromboembolic pulmonary hypertension (CTEPH) have been poorly described. METHODS: We analyzed the data from 2 prospective surgical CTEPH cohorts in Hammersmith Hospital, London, and Amsterdam UMC. A structured multimodal follow-up was adopted, consisting of right heart catheterization, cardiac magnetic resonance imaging, and cardiopulmonary exercise testing before and after PEA. Preoperative predictors of residual pulmonary hypertension (PH; mean pulmonary artery pressure >20 mm Hg and pulmonary vascular resistance ≥2 WU) and long-term exercise intolerance (VO2max <80%) at 18 months were analyzed. RESULTS: A total of 118 patients (61 from London and 57 from Amsterdam) were included in the analysis. Both cohorts displayed a significant improvement of pulmonary hemodynamics, right ventricular (RV) function, and exercise capacity 6 months after PEA. Between 6 and 18 months after PEA, there were no further improvements in hemodynamics and RV function, but the proportion of patients with impaired exercise capacity was high and slightly increased over time (52%-59% from 6 to 18 months). Long-term exercise intolerance was common and associated with preoperative diffusion capacity for carbon monoxide (DLCO), preoperative mixed venous oxygen saturation, and postoperative PH and right ventricular ejection fraction (RVEF). Clinically significant RV deterioration (RVEF decline >3%; 5 [9%] of 57 patients) and recurrent PH (5 [14%] of 36 patients) rarely occurred beyond 6 months after PEA. Age and preoperative DLCO were predictors of residual PH post-PEA. CONCLUSIONS: Restoration in exercise tolerance, cardiopulmonary hemodynamics, and RV function occurs within 6 months. No substantial changes occurred between 6 and 18 months after PEA in the Amsterdam cohort. Nevertheless, long-term exercise intolerance is common and associated with postoperative RV function.

Right ventricular to pulmonary arterial coupling in patients with repaired tetralogy of Fallot: a case series.

Background: In repaired tetralogy of Fallot (ToF) patients with residual right ventricular (RV) outflow tract obstructions (RVOTO), risk stratification and timing of re-interventions are based on RVOTO gradients. However, this might be insufficient to prevent RV dysfunction. Instead, assessment of RV to pulmonary arterial (RV-PA) coupling allows integrated assessment of RV function in relationship to its afterload and could be of additional value in clinical decision-making. Case summary: Two patients with repaired ToF and residual RVOTO without pulmonary regurgitation underwent right heart catheterization (RHC) and cardiac magnetic resonance imaging. We determined RV end-systolic elastance (Ees), arterial elastance (Ea) and RV-PA coupling (Ees/Ea) using single-beat RV pressure-volume analysis. Patient 1 was asymptomatic despite severely increased RV pressures and a left pulmonary artery (LPA) stenosis (invasive gradient 20 mmHg). Right ventricular volumes and function were preserved. The Ea and Ees were increased but RV-PA coupling was relatively maintained. Of interest, RV end-diastolic pressure and RV diastolic stiffness were increased. After LPA plasty, RV function was preserved during long-term follow-up. Patient 2 was symptomatic despite mildly elevated RV pressures and a supravalvular RV-PA conduit stenosis (invasive gradient 30 mmHg). The RV showed severe RV dilatation and dysfunction. The Ea was increased but Ees was decreased leading to RV-PA uncoupling. Despite balloon angioplasty, RV function was unchanged during long-term follow-up. Discussion: Development of RV dysfunction might be insufficiently predicted by RVOTO severity in patients with repaired ToF. Assessment of RV remodelling and function in relationship to its afterload might help to optimize risk stratification.

Geranylgeranylacetone reduces cardiomyocyte stiffness and attenuates diastolic dysfunction in a rat model of cardiometabolic syndrome.

Titin-dependent stiffening of cardiomyocytes is a significant contributor to left ventricular (LV) diastolic dysfunction in heart failure with preserved LV ejection fraction (HFpEF). Small heat shock proteins (HSPs), such as HSPB5 and HSPB1, protect titin and administration of HSPB5 in vitro lowers cardiomyocyte stiffness in pressure-overload hypertrophy. In humans, oral treatment with geranylgeranylacetone (GGA) increases myocardial HSP expression, but the functional implications are unknown. Our objective was to investigate whether oral GGA treatment lowers cardiomyocyte stiffness and attenuates LV diastolic dysfunction in a rat model of the cardiometabolic syndrome. Twenty-one-week-old male lean (n = 10) and obese (n = 20) ZSF1 rats were studied, and obese rats were randomized to receive GGA (200 mg/kg/day) or vehicle by oral gavage for 4 weeks. Echocardiography and cardiac catheterization were performed before sacrifice at 25 weeks of age. Titin-based stiffness (Fpassive ) was determined by force measurements in relaxing solution with 100 nM [Ca2+ ] in permeabilized cardiomyocytes at sarcomere lengths (SL) ranging from 1.8 to 2.4 µm. In obese ZSF1 rats, GGA reduced isovolumic relaxation time of the LV without affecting blood pressure, EF or LV weight. In cardiomyocytes, GGA increased myofilament-bound HSPB5 and HSPB1 expression. Vehicle-treated obese rats exhibited higher cardiomyocyte stiffness at all SLs compared to lean rats, while GGA reduced stiffness at SL 2.0 µm. In obese ZSF1 rats, oral GGA treatment improves cardiomyocyte stiffness by increasing myofilament-bound HSPB1 and HSPB5. GGA could represent a potential novel therapy for the early stage of diastolic dysfunction in the cardiometabolic syndrome.

Long-Term Effects of Pulmonary Endarterectomy on Right Ventricular Stiffness and Fibrosis in Chronic Thromboembolic Pulmonary Hypertension.

BACKGROUND: Surgical removal of thromboembolic material by pulmonary endarterectomy (PEA) leads within months to the improvement of right ventricular (RV) function in the majority of patients with chronic thromboembolic pulmonary hypertension. However, RV mass does not always normalize. It is unknown whether incomplete reversal of RV remodeling results from extracellular matrix expansion (diffuse interstitial fibrosis) or cellular hypertrophy, and whether residual RV remodeling relates to altered diastolic function. METHODS: We prospectively included 25 patients with chronic thromboembolic pulmonary hypertension treated with PEA. Structured follow-up measurements were performed before, and 6 and 18 months after PEA. With single beat pressure-volume loop analyses, we determined RV end-systolic elastance (Ees), arterial elastance (Ea), RV-arterial coupling (Ees/Ea), and RV end-diastolic elastance (stiffness, Eed). The extracellular volume fraction of the RV free wall was measured by cardiac magnetic resonance imaging and used to separate the myocardium into cellular and matrix volume. Circulating collagen biomarkers were analyzed to determine the contribution of collagen metabolism. RESULTS: RV mass significantly decreased from 43±15 to 27±11g/m2 (-15.9 g/m2 [95% CI, -21.4 to -10.5]; P<0.0001) 6 months after PEA but did not normalize (28±9 versus 22±6 g/m2 in healthy controls [95% CI, 2.1 to 9.8]; P<0.01). On the contrary, Eed normalized after PEA. Extracellular volume fraction in the right ventricular free wall increased after PEA from 31.0±3.8 to 33.6±3.5% (3.6% [95% CI, 1.2-6.1]; P=0.013) as a result of a larger reduction in cellular volume than in matrix volume (Pinteraction=0.0013). Levels of MMP-1 (matrix metalloproteinase-1), TIMP-1 (tissue inhibitor of metalloproteinase-1), and TGF-ß (transforming growth factor-ß) were elevated at baseline and remained elevated post-PEA. CONCLUSIONS: Although cellular hypertrophy regresses and diastolic stiffness normalizes after PEA, a relative increase in extracellular volume remains. Incomplete regression of diffuse RV interstitial fibrosis after PEA is accompanied by elevated levels of circulating collagen biomarkers, suggestive of active collagen turnover.

Restoration of right ventricular function in the treatment of pulmonary arterial hypertension.

OBJECTIVE: A 45% threshold of right ventricular ejection fraction (RVEF) is proposed clinically relevant in patients with pulmonary arterial hypertension (PAH). We aim to determine treatment response, long-term right ventricular (RV) functional stability and prognosis of patients with PAH reaching or maintaining the RVEF 45% threshold. METHODS: Incident, treatment-naive, adult PAH patients with cardiac magnetic resonance imaging at baseline and first follow-up were included (total N=127) and followed until date of censoring or death/lung transplantation. Patients were categorised into two groups based on 45% RVEF. Baseline predictors, treatment response and prognosis were assessed with logistic regression analyses, two-way analysis of variance and log-rank tests. RESULTS: Patients were 50±17 years old, 73% female, of which N=75 reached or maintained the 45% RVEF threshold at follow-up (RVEF≥45%@FU), while N=52 patients did not (RVEF<45%@FU). RV end-diastolic volume and N-terminal pro-B-type natriuretic peptide at baseline were multivariable predictors of an RVEF ≥45% at follow-up. A 40% pulmonary vascular resistance (PVR) reduction resulted in greater improvement in RV function (ΔRVEF 17±11 vs. 5±8; pinteraction<0.001) compared to a PVR reduction <40%, but did not guarantee an RVEF ≥45%. Finally, the 45% RVEF threshold was associated with stable RV function during long-term follow-up and better survival (HR: 1.91 (95% CI: 1.11 to 3.27)). Patients failing to reach or maintain the 45% RVEF threshold at first follow-up mostly stayed below this threshold over the next consecutive visits. CONCLUSION: After treatment initiation, 60% of patients with PAH reach or maintain the 45% RVEF threshold, which is associated with a long-term stable RV function and favourable prognosis.

Trimetazidine in heart failure with preserved ejection fraction: a randomized controlled cross-over trial.

AIMS: Impaired myocardial energy homeostasis plays an import role in the pathophysiology of heart failure with preserved ejection fraction (HFpEF). Left ventricular relaxation has a high energy demand, and left ventricular diastolic dysfunction has been related to impaired energy homeostasis. This study investigated whether trimetazidine, a fatty acid oxidation inhibitor, could improve myocardial energy homeostasis and consequently improve exercise haemodynamics in patients with HFpEF. METHODS AND RESULTS: The DoPING-HFpEF trial was a phase II single-centre, double-blind, placebo-controlled, randomized cross-over trial. Patients were randomized to trimetazidine treatment or placebo for 3 months and switched after a 2-week wash-out period. The primary endpoint was change in pulmonary capillary wedge pressure, measured with right heart catheterization at multiple stages of bicycling exercise. Secondary endpoint was change in myocardial phosphocreatine/adenosine triphosphate, an index of the myocardial energy status, measured with phosphorus-31 magnetic resonance spectroscopy. The study included 25 patients (10/15 males/females; mean (standard deviation) age, 66 (10) years; body mass index, 29.8 (4.5) kg/m2 ); with the diagnosis of HFpEF confirmed with (exercise) right heart catheterization either before or during the trial. There was no effect of trimetazidine on the primary outcome pulmonary capillary wedge pressure at multiple levels of exercise (mean change 0 [95% confidence interval, 95% CI -2, 2] mmHg over multiple levels of exercise, P = 0.60). Myocardial phosphocreatine/adenosine triphosphate in the trimetazidine arm was similar to placebo (1.08 [0.76, 1.76] vs. 1.30 [0.95, 1.86], P = 0.08). There was no change by trimetazidine compared with placebo in the exploratory parameters: 6-min walking distance (mean change of -6 [95% CI -18, 7] m vs. -5 [95% CI -22, 22] m, respectively, P = 0.93), N-terminal pro-B-type natriuretic peptide (5 (-156, 166) ng/L vs. -13 (-172, 147) ng/L, P = 0.70), overall quality-of-life (KCCQ and EQ-5D-5L, P = 0.78 and P = 0.51, respectively), parameters for diastolic function measured with echocardiography and cardiac magnetic resonance, or metabolic parameters. CONCLUSIONS: Trimetazidine did not improve myocardial energy homeostasis and did not improve exercise haemodynamics in patients with HFpEF.

Right Atrial Adaptation to Precapillary Pulmonary Hypertension: Pressure-Volume, Cardiomyocyte, and Histological Analysis.

BACKGROUND: Precapillary pulmonary hypertension (precPH) patients have altered right atrial (RA) function and right ventricular (RV) diastolic stiffness. OBJECTIVES: This study aimed to investigate RA function using pressure-volume (PV) loops, isolated cardiomyocyte, and histological analyses. METHODS: RA PV loops were constructed in control subjects (n = 9) and precPH patients (n = 27) using magnetic resonance and catheterization data. RA stiffness (pressure rise during atrial filling) and right atrioventricular coupling index (RA minimal volume / RV end-diastolic volume) were compared in a larger cohort of patients with moderate (n = 39) or severe (n = 41) RV diastolic stiffness. Cardiomyocytes were isolated from RA tissue collected from control subjects (n = 6) and precPH patients (n = 9) undergoing surgery. Autopsy material was collected from control subjects (n = 6) and precPH patients (n = 4) to study RA hypertrophy, capillarization, and fibrosis. RESULTS: RA PV loops showed 3 RA cardiac phases (reservoir, passive emptying, and contraction) with dilatation and elevated pressure in precPH. PrecPH patients with severe RV diastolic stiffness had increased RA stiffness and worse right atrioventricular coupling index. Cardiomyocyte cross-sectional area was increased 2- to 3-fold in precPH, but active tension generated by the sarcomeres was unaltered. There was no increase in passive tension of the cardiomyocytes, but end-stage precPH showed reduced number of capillaries per mm2 accompanied by interstitial and perivascular fibrosis. CONCLUSIONS: RA PV loops show increased RA stiffness and suggest atrioventricular uncoupling in patients with severe RV diastolic stiffness. Isolated RA cardiomyocytes of precPH patients are hypertrophied, without intrinsic sarcomeric changes. In end-stage precPH, reduced capillary density is accompanied by interstitial and perivascular fibrosis.

The Right Ventricle in Pulmonary Hypertension.

The right ventricle plays a pivotal role in patients with pulmonary hypertension (PH). Its adaptation to pressure overload determines a patient's functional status as well as survival. In a healthy situation, the right ventricle is part of a low pressure, high compliance system. It is built to accommodate changes in preload, but not very well suited for dealing with pressure overload. In PH, right ventricular (RV) contractility must increase to maintain cardiac output. In other words, the balance between the degree of RV contractility and afterload determines stroke volume. Hypertrophy is one of the major hallmarks of RV adaptation, but it may cause stiffening of the ventricle in addition to intrinsic changes to the RV myocardium. Ventricular filling becomes more difficult for which the right atrium tries to compensate through increased stroke work. Interaction of RV diastolic stiffness and right atrial (RA) function determines RV filling, but also causes vena cava backflow. Assessment of RV and RA function is critical in the evaluation of patient status. In recent guidelines, this is acknowledged by incorporating additional RV parameters in the risk stratification in PH. Several conventional parameters of RV and RA function have been part of risk stratification for many years. Understanding the pathophysiology of RV failure and the interactions with the pulmonary circulation and right atrium requires consideration of the unique RV anatomy. This review will therefore describe normal RV structure and function and changes that occur during adaptation to increased afterload. Consequences of a failing right ventricle and its implications for RA function will be discussed. Subsequently, we will describe RV and RA assessment in clinical practice.

How to incorporate tricuspid regurgitation in right ventricular-pulmonary arterial coupling.

Adaptation of the right ventricle (RV) to a progressively increasing afterload is one of the hallmarks of pulmonary arterial hypertension (PAH). Pressure-volume loop analysis provides measures of load-independent RV contractility, i.e., end-systolic elastance, and pulmonary vascular properties, i.e., effective arterial elastance (Ea). However, PAH-induced RV overload potentially results in tricuspid regurgitation (TR). TR makes RV eject to both PA and right atrium; thereby, a ratio of RV end-systolic pressure (Pes) to RV stroke volume (SV) could not correctly define Ea. To overcome this limitation, we introduced a two-parallel compliance model, i.e., Ea = 1/(1/Epa + 1/ETR), while effective pulmonary arterial elastance (Epa = Pes/PASV) represents pulmonary vascular properties and effective tricuspid regurgitant elastance (ETR) represents TR. We conducted animal experiments to validate this framework. First, we performed SV analysis with a pressure-volume catheter in the RV and a flow probe at the aorta in rats with and without pressure-overloaded RV to determine the effect of inferior vena cava (IVC) occlusion on TR. A discordance between the two techniques was found in rats with pressure-overloaded RV, not in sham. This discordance diminished after IVC occlusion, suggesting that TR in pressure-overloaded RV was diminished by IVC occlusion. Next, we performed pressure-volume loop analysis in rats with pressure-overloaded RVs, calibrating RV volume by cardiac magnetic resonance. We found that IVC occlusion increased Ea, suggesting that a reduction of TR increased Ea. Using the proposed framework, Epa was indistinguishable to Ea post-IVC occlusion. We conclude that the proposed framework helps better understanding of the pathophysiology of PAH and associated right heart failure.NEW & NOTEWORTHY This study reveals the impact of tricuspid regurgitation on pressure-volume loop analysis in right ventricle pressure overload. By introducing a novel concept of parallel compliances in the pressure-volume loop analysis, a better description is provided for the right ventricular forward afterload in the presence of tricuspid regurgitation.