Early detection of pulmonary arterial hypertension: do not forget the right ventricle

Structural and Hemodynamic Changes of the Right Ventricle in PH-HFpEF

One of the most important diagnostic challenges in clinical practice is the distinction between pulmonary hypertension (PH) due to primitive pulmonary arterial hypertension (PAH) and PH due to left heart diseases. Both conditions share some common characteristics and pathophysiological pathways, making the two processes similar in several aspects. Their diagnostic differentiation is based on hemodynamic data on right heart catheterization, cardiac structural modifications, and therapeutic response. More specifically, PH secondary to heart failure with preserved ejection fraction (HFpEF) shares features with type 1 PH (PAH), especially when the combined pre- and post-capillary form (CpcPH) takes place in advanced stages of the disease. Right ventricular (RV) dysfunction is a common consequence related to worse prognosis and lower survival. This condition has recently been identified with a new classification based on clinical signs and progression markers. The role and prevalence of PH and RV dysfunction in HFpEF remain poorly identified, with wide variability in the literature reported from the largest clinical trials. Different parenchymal and vascular alterations affect the two diseases. Capillaries and arteriole vasoconstriction, vascular obliteration, and pulmonary blood fluid redistribution from the basal to the apical district are typical manifestations of type 1 PH. Conversely, PH related to HFpEF is primarily due to an increase of venules/capillaries parietal fibrosis, extracellular matrix deposition, and myocyte hypertrophy with a secondary “arteriolarization” of the vessels. Since the development of structural changes and the therapeutic target substantially differ, a better understanding of pathobiological processes underneath PH-HFpEF, and the identification of potential maladaptive RV mechanisms with an appropriate diagnostic tool, become mandatory in order to distinguish and manage these two similar forms of pulmonary hypertension.

Pulmonary arterial hypertension and heart failure with preserved ejection fraction: are they so discordant?

Heart failure with preserved ejection fraction (HFpEF) and pulmonary arterial hypertension (PAH) are two emerging diseases focusing the attention of numerous researchers. In the last PAH guideline, there is a crossroad between the two diseases and pulmonary hypertension (PH) due to heart failure (HF) is categorized as subtype 2. In order to assess the correct diagnosis and management, it should be better understood the points of convergence and divergence of two diseases. Although, risk factors, demographic characteristics and haemodynamics are different, we report several similarities regarding vascular alterations, some aspects of cardiac remodelling, and clinical presentation. This model suggests HFpEF and PAH as two comparable conditions, with different cardiac adaptation and trajectories, linked to the intrinsic properties of either right and left ventricles. In both diseases the early pathophysiological mechanisms appear to begin from peripheral vasculature and to be backward transmitted to the larger arterial vascular district, and eventually to the myocardial structure. In this paper we would propose a simple approach to recognize the concordances and, all at once, distinguish the peculiarities of the two diseases.

Neuregulin-1 attenuates right ventricular diastolic stiffness in experimental pulmonary hypertension

We have previously shown that treatment with recombinant human neuregulin-1 (rhNRG-1) improves pulmonary arterial hypertension (PAH) in a monocrotaline (MCT)-induced animal model, by decreasing pulmonary arterial remodelling and endothelial dysfunction, as well as by restoring right ventricular (RV) function. Additionally, rhNRG-1 treatment showed direct myocardial anti-remodelling effects in a model of pressure loading of the RV without PAH. This work aimed to study the intrinsic cardiac effects of rhNRG-1 on experimental PAH and RV pressure overload, and more specifically on diastolic stiffness, at both the ventricular and cardiomyocyte level. We studied the effects of chronic rhNRG-1 treatment on ventricular passive stiffness in RV and LV samples from MCT-induced PAH animals and in the RV from animals with compensated and decompensated RV hypertrophy, through a mild and severe pulmonary artery banding (PAB). We also measured passive tension in isolated cardiomyocytes and quantified the expression of myocardial remodelling-associated genes and calcium handling proteins. Chronic rhNRG-1 treatment decreased passive tension development in RV and LV isolated from animals with MCT-induced PAH. This decrease was associated with increased phospholamban phosphorylation, and with attenuation of the expression of cardiac maladaptive remodelling markers. Finally, we showed that rhNRG-1 therapy decreased RV remodelling and cardiomyocyte passive tension development in PAB-induced RV hypertrophy animals, without compromising cardiac function, pointing to cardiac-specific effects in both hypertrophy stages. In conclusion, we demonstrated that rhNRG-1 treatment decreased RV intrinsic diastolic stiffness, through the improvement of calcium handling and cardiac remodelling signalling.

Natural Antioxidants as Potential Therapy, and a Promising Role for Melatonin Against Pulmonary Hypertension

Plasma and serum samples, and lung/heart tissue of pulmonary hypertension (PH) patients and animal models of PH display elevated oxidative stress. Moreover, the severity of PH and levels of oxidative stress increase concurrently, which suggests that oxidative stress could be utilized as a biomarker for PH progression. Accumulating evidence has well established that oxidative stress is also key role player in the development of PH. Preclinical studies have demonstrated that natural antioxidants improved PH condition, and, therefore, antioxidant therapy has been proposed as a potential therapeutic strategy against PH. These natural antioxidants include medicinal plant extracts and compounds such as resveratrol and melatonin. Recent studies suggest that melatonin provides health benefit against PH, by enhancing antioxidant capacity, increasing vasodilation, counteracting lung and cardiac fibrosis, and stunting right ventricular (RV) hypertrophy/failure. This chapter comprehensively reviews and discusses a variety of natural antioxidants and their efficacy in modulating experimental PH. This chapter also demonstrates that antioxidant therapy remains a therapeutic strategy for PH, and particularly identifies melatonin as a safe, cost-effective, and promising antioxidant therapy.