Vagal nerve stimulation preserves right ventricular function in a rat model of right ventricular pressure overload.

Vagal nerve stimulation (VNS) ameliorates pulmonary vascular remodeling and improves survival in a rat model of pulmonary hypertension (PH). However, the direct impact of VNS on right ventricular (RV) function, which is the key predictor of PH patients, remains unknown. We evaluated the effect of VNS among the three groups: pulmonary artery banding (PAB) with sham stimulation (SS), PAB with VNS, and control (no PAB). We stimulated the right cervical vagal nerve with an implantable pulse generator, initiated VNS 2 weeks after PAB, and stimulated for 2 weeks. Compared to SS, VNS increased cardiac index (VNS: 130 ± 10 vs. SS: 93 ± 7 ml/min/kg; p < 0.05) and end-systolic elastance assessed by RV pressure-volume analysis (VNS: 1.1 ± 0.1 vs. SS: 0.7 ± 0.1 mmHg/µl; p < 0.01), but decreased RV end-diastolic pressure (VNS: 4.5 ± 0.7 vs. SS: 7.7 ± 1.0 mmHg; p < 0.05). Furthermore, VNS significantly attenuated RV fibrosis and CD68-positive cell migration. In PAB rats, VNS improved RV function, and attenuated fibrosis, and migration of inflammatory cells. These results provide a rationale for VNS therapy as a novel approach for RV dysfunction in PH patients.

Right Ventricular and Right Atrial Function Are Less Compromised in Pulmonary Hypertension Secondary to Heart Failure With Preserved Ejection Fraction: A Comparison With Pulmonary Arterial Hypertension With Similar Pressure Overload.

BACKGROUND: Heart failure with preserved ejection fraction (HFpEF) is a prevalent disorder for which no effective treatment yet exists. Pulmonary hypertension (PH) and right atrial (RA) and ventricular (RV) dysfunction are frequently observed. The question remains whether the PH with the associated RV/RA dysfunction in HFpEF are markers of disease severity. METHODS: To obtain insight in the relative importance of pressure-overload and left-to-right interaction, we compared RA and RV function in 3 groups: 1. HFpEF (n=13); 2. HFpEF-PH (n=33), and; 3. pulmonary arterial hypertension (PAH) matched to pulmonary artery pressures of HFpEF-PH (PH limited to mPAP ≥30 and ≤50 mmHg) (n=47). Patients underwent right heart catheterization and cardiac magnetic resonance imaging. RESULTS: The right ventricle in HFpEF-PH was less dilated and hypertrophied than in PAH. In addition, RV ejection fraction was more preserved (HFpEF-PH: 52±11 versus PAH: 36±12%). RV filling patterns differed: vena cava backflow during RA contraction was observed in PAH only. In HFpEF-PH, RA pressure was elevated throughout the cardiac cycle (HFpEF-PH: 10 [8-14] versus PAH: 7 [5-10] mm Hg), while RA volume was smaller, reflecting excessive RA stiffness (HFpEF-PH: 0.14 [0.10-0.17] versus PAH: 0.08 [0.06-0.11] mm Hg/mL). RA stiffness was associated with an increased eccentricity index (HFpEF-PH: 1.3±0.2 versus PAH: 1.2±0.1) and interatrial pressure gradient (9 [5 to 12] versus 2 [-2 to 5] mm Hg). CONCLUSIONS: RV/RA function was less compromised in HFpEF-PH than in PAH, despite similar pressure-overload. Increased RA pressure and stiffness in HFpEF-PH were explained by left atrial/RA-interaction. Therefore, our results indicate that increased RA pressure is not a sign of overt RV failure but rather a reflection of HFpEF-severity.

Uptake and Patient Perspectives on Additional Testing for Novel Disease-Associated Genes: Lessons from a PAH Cohort.

BACKGROUND: Pulmonary arterial hypertension (PAH) has an identifiable genetic cause in 5% of all PAH cases. Due to health benefits conferred by the early detection of PAH and the recent identification of additional PAH-associated genes, we decided to offer (extended) genetic testing to all incident and prevalent idiopathic PAH (iPAH) and pulmonary veno-occlusive disease (PVOD) patients in our clinic. Here, we report the lessons learned from (re-)contacting iPAH/PVOD patients concerning the uptake and analysis of identified PAH-associated genes and patient perspectives of the approach. METHODS: Between January 2018 and April 2020, all iPAH/PVOD patients who were not previously genetically tested (contact group) and those who tested negative on prior analysis of BMPR2 and SMAD9 variants (re-contact group) were (re-)contacted for (additional) genetic testing. RESULTS: With our approach, 58% of patients (84 out of 165) opted for genetic counselling, and a pathogenic variant was found in 12% of cases (n = 10) (re-contact group, 11%, and contact group, 13%). Eighty-six percent of participants of the survey study appreciated being (re-)contacted for genetic testing. Mild psychosocial impacts were observed. CONCLUSIONS: Our report shows the importance of (re-)contact and interest of patients (as indicated by the uptake, mild psychosocial impact and appreciation) in PAH.

Elevated acute phase proteins affect pharmacokinetics in COVID-19 trials: Lessons from the CounterCOVID - imatinib study.

This study aimed to determine whether published pharmacokinetic (PK) models can adequately predict the PK profile of imatinib in a new indication, such as coronavirus disease 2019 (COVID-19). Total (bound + unbound) and unbound imatinib plasma concentrations obtained from 134 patients with COVID-19 participating in the CounterCovid study and from an historical dataset of 20 patients with gastrointestinal stromal tumor (GIST) and 85 patients with chronic myeloid leukemia (CML) were compared. Total imatinib area under the concentration time curve (AUC), maximum concentration (Cmax ) and trough concentration (Ctrough ) were 2.32-fold (95% confidence interval [CI] 1.34-3.29), 2.31-fold (95% CI 1.33-3.29), and 2.32-fold (95% CI 1.11-3.53) lower, respectively, for patients with CML/GIST compared with patients with COVID-19, whereas unbound concentrations were comparable among groups. Inclusion of alpha1-acid glycoprotein (AAG) concentrations measured in patients with COVID-19 into a previously published model developed to predict free imatinib concentrations in patients with GIST using total imatinib and plasma AAG concentration measurements (AAG-PK-Model) gave an estimated mean (SD) prediction error (PE) of -20% (31%) for total and -7.0% (56%) for unbound concentrations. Further covariate modeling with this combined dataset showed that in addition to AAG; age, bodyweight, albumin, CRP, and intensive care unit admission were predictive of total imatinib oral clearance. In conclusion, high total and unaltered unbound concentrations of imatinib in COVID-19 compared to CML/GIST were a result of variability in acute phase proteins. This is a textbook example of how failure to take into account differences in plasma protein binding and the unbound fraction when interpreting PK of highly protein bound drugs, such as imatinib, could lead to selection of a dose with suboptimal efficacy in patients with COVID-19.

Therapeutic potential of KLF2-induced exosomal microRNAs in pulmonary hypertension.

Pulmonary arterial hypertension (PAH) is a severe disorder of lung vasculature that causes right heart failure. Homoeostatic effects of flow-activated transcription factor Krüppel-like factor 2 (KLF2) are compromised in PAH. Here, we show that KLF2-induced exosomal microRNAs, miR-181a-5p and miR-324-5p act together to attenuate pulmonary vascular remodelling and that their actions are mediated by Notch4 and ETS1 and other key regulators of vascular homoeostasis. Expressions of KLF2, miR-181a-5p and miR-324-5p are reduced, while levels of their target genes are elevated in pre-clinical PAH, idiopathic PAH and heritable PAH with missense p.H288Y KLF2 mutation. Therapeutic supplementation of miR-181a-5p and miR-324-5p reduces proliferative and angiogenic responses in patient-derived cells and attenuates disease progression in PAH mice. This study shows that reduced KLF2 signalling is a common feature of human PAH and highlights the potential therapeutic role of KLF2-regulated exosomal miRNAs in PAH and other diseases associated with vascular remodelling.

Pressure overload induced right ventricular remodeling is not attenuated by the anti-fibrotic agent pirfenidone.

Cardiac fibrosis contributes to the development of heart failure in pulmonary hypertension. We aimed to assess the development of fibrosis and the effects of treatment with the anti-fibrotic agent pirfenidone in pressure overload induced right ventricular (RV) failure. Wistar rat weanlings were randomized to pulmonary trunk banding (PTB) or sham surgery. One week after the procedure, PTB rats were randomized into two groups with either six weeks on standard chow or treatment with pirfenidone mixed in chow (700 mg/kg/day). RV hemodynamic effects were evaluated by echocardiography, cardiac magnetic resonance imaging (MRI), and pressure-volume measurements. Sections from the isolated RV, left ventricle, and septum were sampled systematically; stereological point grids and the nucleator were used to estimate volume of fibrosis and cardiac hypertrophy, respectively. PTB caused RV failure in all rats subjected to the procedure. The volume fraction of fibrosis in the RV increased threefold in PTB rats corresponding to a sixfold increase in total volume of RV fibrosis. Volume fraction of fibrosis and total volume of fibrosis also increased in the septum and in the left ventricle. Pirfenidone reduced body weight but did not improve RV hemodynamics or reduce cardiac fibrosis. RV cardiomyocyte profile area was increased twofold in PTB rats without any effect of pirfenidone. RV pressure overload after PTB induced not only RV but also septal and left ventricular fibrosis assessed by stereology. Treatment with pirfenidone reduced body weight but did not reduce the development of cardiac fibrosis or delay the progression of RV failure.

Treatment response in patients with idiopathic pulmonary arterial hypertension and a severely reduced diffusion capacity.

Patients with idiopathic pulmonary arterial hypertension (IPAH) and a reduced diffusion capacity of the lung for carbon monoxide (DLCO) have a worse survival compared to IPAH patients with a preserved DLCO. Whether this poor survival can be explained by unresponsiveness to pulmonary hypertension (PH)-specific vasodilatory therapy is unknown. Therefore, the aim of this study was to evaluate the hemodynamic and cardiac response to PH-specific vasodilatory therapy in patients with IPAH and a reduced DLCO. Retrospectively, we studied treatment naïve hereditary and IPAH patients diagnosed between January 1990 and May 2015 at the VU University Medical Center. After exclusion of participants without available baseline DLCO measurement or right heart catheterization data and participants carrying a BMPR2 mutation, 166 participants could be included in this study. Subsequently, hemodynamics, cardiac function, exercise capacity, and oxygenation at baseline and after PH-specific vasodilatory therapy were compared between IPAH patients with a preserved DLCO (DLCO >62%), IPAH patients with a moderately reduced DLCO (DLCO 43-62%), and IPAH patients with a severely reduced DLCO (DLCO <43%). Baseline hemodynamics and right ventricular function were not different between groups. Baseline oxygenation was worse in patients with IPAH and a severely reduced DLCO. Hemodynamics and cardiac function improved in all groups after PH-specific vasodilatory therapy without worsening of oxygenation at rest or during exercise. Patients with IPAH and a severely reduced DLCO show a similar response to PH-specific vasodilatory therapy in terms of hemodynamics, cardiac function, and exercise capacity as patients with IPAH and a moderately reduced or preserved DLCO.

Reversal of right ventricular remodeling by dichloroacetate is related to inhibition of mitochondria-dependent apoptosis.

Most patients with pulmonary arterial hypertension die from right ventricular failure (RVF). Right ventricular (RV) myocardial apoptosis has an important role in RVF and is regulated by the mitochondria. Dichloroacetate (DCA) can improve cardiac function in RVF, but whether it can regulate myocardial apoptosis via mitochondria is still unknown. In this study, we investigated the effects of DCA on myocardial mitochondria, the mitochondrial apoptosis and other aspects of RV remodeling, including fibrosis and capillary rarefaction. RVF was induced in rats by a single s.c. injection of monocrotaline. After 4 weeks, DCA treatment was started with i.p. injection of 50, 150 or 2007 mg kg(-1) per day during 14 days. Compared with saline-treated RVF animals, treatment with DCA resulted in decreased mean pulmonary arterial pressure and total pulmonary resistance (TPR), and increased cardiac output. The expression of pyruvate dehydrogenase kinase was suppressed, while pyruvate dehydrogenase expression was upregulated with DCA application. DCA treatment was also associated with restored RV mitochondrial function and a reduction in RV hypertrophy, fibrosis, capillary rarefaction and apoptosis. Mitochondria-dependent apoptosis was involved in DCA regulation of RV. The absent correlation between TPR and main parameters in RV suggests that the effects of DCA in the two organ systems are independent. We conclude that DCA improves cardiac function in experimental RVF partly by reversing RV remodeling, restoring mitochondrial function and regulating mitochondria-dependent apoptosis. The study shows that a fear for increased RV apoptosis with DCA treatment is unnecessary and suggests a potential role of DCA in the treatment of RVF.