Clinical correlates of a non-plexiform vasculopathy in patients diagnosed with idiopathic pulmonary arterial hypertension

BACKGROUND

The clinical phenotype of idiopathic pulmonary arterial hypertension (IPAH) patients has changed. . Whether or not subgroups of IPAH patients have different vascular phenotypes is a subject of debate.

RESEARCH QUESTION

What are the histological patterns and their clinical correlates in patients diagnosed with IPAH or hereditary PAH?

STUDY DESIGN AND METHODS

In this this cross-sectional registry study lung histology of 50 IPAH patients was qualitatively assessed by two experienced pathologists. In addition, quantitative analysis by means of histopathological morphometry using immunohistochemistry was performed. Histopathological characteristics were correlated with clinical and hemodynamic parameters.

RESULTS

In this cohort of 50 IPAH patients, a plexiform vasculopathy was observed in 26/50 (52%) of patients, while 24/50 (48%) patients had a non-plexiform vasculopathy. The non-plexiform vasculopathy was characterized by prominent pulmonary microvascular (arterioles and venules) remodeling and vascular rarefaction. While hemodynamic parameters were comparable in plexiform versus non-plexiform vasculopathy, patients with non-plexiform vasculopathy were older, more often male, had a stronger history of cigarette smoking and lower diffusing capacity for carbon monoxide (DLCO) at diagnosis No mutations in established PAH genes were found in the non-plexiform group.

INTERPRETATION

This study reveals different vascular phenotypes within the current spectrum of patients diagnosed with IPAH, separated by clinical characteristics (age, sex, , history of cigarette smoking, and DLCO at diagnosis). Potential differences in underlying pathobiological mechanisms between patients with plexiform and non-plexiform / microvascular disease should be taken into account in future research strategies unravelling the pathophysiology of pulmonary hypertension and developing biology-targeted treatment approaches.

Trimetazidine in heart failure with preserved ejection fracton: a randomized, double-blind cross-over trial

Introduction

Impaired myocardial mitochondrial function plays an import role in the pathophysiology of heart failure with preserved ejection fraction (HFpEF). Left ventricular relaxation has a high energy demand, and there is evidence indicative of a causal relationship between observed impaired energy homeostasis and diastolic dysfunction. Improvement of mitochondrial function with metabolism-modulating drugs may be a promising novel therapeutic approach in HFpEF. Trimetazidine – a fatty acid oxidation inhibitor – shifts mitochondrial metabolism towards glucose oxidation, which results in higher mitochondrial oxygen efficiency. In this study we investigated whether trimetazidine improves diastolic function during exercise in HFpEF by improving the myocardial energy homeostasis.

Methods

The DoPING-HFpEF trial was a phase II single-center, double-blind, placebo-controlled, randomized cross-over trial. The study consisted of two treatment periods of three months separated by a 2-week wash-out period (Figure 1). Patients were treated with placebo or trimetazidine three times a day (or twice daily in case of an impaired kidney function). The primary endpoint was change in pulmonary capillary wedge pressure (PCWP) measured with right heart catheterization at multiple stages of exercise. Secondary endpoint was change in phosphocreatine (PCr)/adenosine triphosphate (ATP) ratio, an index of the myocardial energy status, measured with phosphorus-31 magnetic resonance (MR) spectroscopy. Additional exploratory endpoints were 6-minute-walking-distance, diastolic and systolic parameters measured with echocardiography or cardiac MR, NT-proBNP levels, and quality of life.

Results

Twenty-five HFpEF patients were included and completed the trial, 80% of which were included based on previously established elevated (exercise) PCWP, and 20% were included based on diastolic dysfunction grade ≥II on echocardiography and elevated NT-proBNP levels. There was no effect on the primary outcome PCWP at multiple levels of exercise, with an average change in PCWP of 0±4 (SD) mmHg (Figure 2A, P=0.97). Myocardial PCr/ATP in the trimetazidine arm was similar to placebo (Figure 2B, P=0.08). There was no change by trimetazidine in the exploratory parameters 6-minute walking distance, NT-proBNP, overall quality of life, or other parameters for diastolic function measured with echocardiography and cardiac MR. There was no indication of period or cross over effect.

Conclusion

Trimetazidine did not improve diastolic function or myocardial energy homeostasis in patients with HFpEF.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Dutch Heart Foundation (DHF) and “Out-of-the-Box” grant from the Amsterdam Cardiovascular Sciences (ACS) Institute, Amsterdam, The Netherlands.

The adult heart requires baseline expression of the transcription factor Hand2 to withstand RV pressure overload

AIMS

Research on the pathophysiology of right ventricular (RV) failure has, in spite of the associated high mortality and morbidity, lagged behind compared to the left ventricle (LV).Previous work from our lab revealed that the embryonic basic helix-loop-helix transcription factor heart and neural crest derivatives expressed-2 (Hand2) is re-expressed in the adult heart and activates a 'fetal gene program' contributing to pathological cardiac remodeling under conditions of LV pressure overload. As such, ablation of cardiac expression of Hand2 conferred protection to cardiac stress and abrogated the maladaptive effects that were observed upon increased expression levels. In this study, we aimed to understand the contribution of Hand2 to RV remodeling in response to pressure overload induced by pulmonary artery banding (PAB).

METHODS AND RESULTS

In the present study, Hand2F/F and MCM- Hand2F/F mice were treated with tamoxifen (control and knockout, respectively) and subjected to six weeks of RV pressure overload induced by PAB. Echocardiographic- and MRI-derived hemodynamic parameters as well as molecular remodeling were assessed for all experimental groups and compared to sham-operated controls. Six weeks after PAB, levels of Hand2 expression increased in the control banded animals but, as expected, remained absent in the knockout hearts. Despite the dramatic differences in Hand2 expression, pressure overload resulted in impaired cardiac function independently of the genotype. In fact, Hand2 depletion seems to sensitize the RV to pressure overload as these mice develop more hypertrophy and more severe cardiac dysfunction. Higher expression levels of HAND2 were also observed in RV samples of human hearts from patients with pulmonary hypertension. In turn, the LV of RV-pressure overloaded hearts was also dramatically affected as reflected by changes in shape, decreased LV mass and impaired cardiac function. RNA sequencing revealed a distinct set of genes that are dysregulated in the pressure-overloaded RV, compared to the previously described pressure-overloaded LV.

CONCLUSIONS

Cardiac-specific depletion of Hand2 is associated with severe cardiac dysfunction in conditions of RV pressure overload. While inhibiting Hand2 expression can prevent cardiac dysfunction in conditions of LV pressure overload, the same does not hold true for conditions of RV pressure overload. This study highlights the need to better understand the molecular mechanisms driving pathological remodeling of the RV in contrast to the LV, in order to better diagnose and treat patients with RV or LV failure.

TRANSLATIONAL PERSPECTIVE

RV failure associated with pulmonary hypertension reduces long-term survival rate to 55% within 3 years, suggesting that 3 years after diagnosis almost half of the patients will die. To revert these numbers an adequate RV-specific and, therefore, more efficient treatment is needed. Our work suggests that current therapies and potential mechanisms underlying LV failure may not be suitable for RV failure. While Hand2 deletion is favorable in LV response to stress, it is particularly detrimental in the RV under similar conditions, and thus, highlighting potential severe consequences of not differentiating therapeutic targets or treatment for RV or LV failure.