Pathophysiology and potential treatments of pulmonary hypertension due to systolic left heart failure

Heart‑lung crosstalk in pulmonary arterial hypertension following myocardial infarction (Review)

Left heart disease is the main cause of clinical pulmonary arterial hypertension (PAH). Common types of left heart disease that result in PAH include heart failure, left ventricular systolic dysfunction, left ventricular diastolic dysfunction and valvular disease. It is currently believed that mechanical pressure caused by high pulmonary venous pressure is the main cause of myocardial infarction (MI) in individuals with ischemic cardiomyopathy and left ventricular systolic dysfunction. In the presence of decreased cardiac function, vascular remodeling of pulmonary vessels in response to long-term stimulation by high pressure in turn leads to exacerbation of PAH. However, the underlying pathological mechanisms remain unclear. Elucidating the association between the development of MI and PAH may lead to a better understanding of potential risk factors and better disease treatment. In this article, the pathophysiological effects of multiple systems in individuals with MI and PAH were reviewed in order to provide a general perspective on various potential interactions between cardiomyocytes and pulmonary vascular cells.

Plasma receptor tyrosine kinase RET in pulmonary arterial hypertension diagnosis and differentiation

Background

Pulmonary arterial hypertension (PAH) is a serious disease exhibiting unspecific symptoms, as a result of which diagnosis is often delayed and prognosis is poor. The underlying pathophysiology includes vasoconstriction and remodelling of small pulmonary arteries. As receptor tyrosine kinases (RTKs) and their ligands have been shown to promote PAH remodelling, our aim was to evaluate if their plasma levels may be utilised to differentiate between various causes of pulmonary hypertension.

Methods

28 biomarkers involved in RTK signalling were measured using proximity extension assays in venous plasma from patients with PAH (n=48), chronic thromboembolic pulmonary hypertension (CTEPH) (n=20), pulmonary hypertension due to diastolic (n=33) or systolic (n=36) heart failure and heart failure patients without pulmonary hypertension (n=15), as well as healthy controls (n=20).

Results

Plasma proto-oncogene tyrosine-protein kinase receptor Ret (RET) was decreased (p<0.04) in PAH compared with all disease groups and controls. RET generated a sensitivity of 64.6% and a specificity of 81.6% for detecting PAH from other disease groups. PAH and the other pulmonary hypertension groups showed elevated plasma tyrosine-protein kinase MER (p<0.01), vascular endothelial growth factor (VEGF)-A (p<0.02), VEGF-D (p<0.01), placental growth factor (p<0.01), amphiregulin (p<0.02), hepatocyte growth factor (p<0.01) and transforming growth factor-α (p<0.05) and decreased VEGF receptor-2 (p<0.04) and epidermal growth factor receptor (p<0.01) levels compared with controls.

Conclusion

Plasma RET differentiates patients with PAH from those with CTEPH, systolic or diastolic heart failure with or without pulmonary hypertension as well as healthy controls. Future studies would be of value to determine the clinical usefulness of RET as a biomarker and its link to PAH pathophysiology.

Receptor tyrosine kinases have been shown to promote PAH remodelling. Plasma RET differentiates PAH from other causes of PH. RET could have the potential to be used as a future diagnostic biomarker.http://bit.ly/2LChPUS

Intervening with the Nitric Oxide Pathway to Alleviate Pulmonary Hypertension in Pulmonary Vein Stenosis

Pulmonary hypertension (PH) as a result of pulmonary vein stenosis (PVS) is extremely difficult to treat. The ideal therapy should not target the high-pressure/low-flow (HP/LF) vasculature that drains into stenotic veins, but only the high-pressure/high-flow (HP/HF) vasculature draining into unaffected pulmonary veins, reducing vascular resistance and pressure without risk of pulmonary oedema. We aimed to assess the activity of the nitric oxide (NO) pathway in PVS during the development of PH, and investigate whether interventions in the NO pathway differentially affect vasodilation in the HP/HF vs. HP/LF territories. Swine underwent pulmonary vein banding (PVB; n = 7) or sham surgery (n = 6) and were chronically instrumented to assess progression of PH. Pulmonary sensitivity to exogenous NO (sodium nitroprusside, SNP) and the contribution of endogenous NO were assessed bi-weekly. The pulmonary vasodilator response to phosphodiesterase-5 (PDE5) inhibition was assessed 12 weeks after PVB or sham surgery. After sacrifice, 12 weeks post-surgery, interventions in the NO pathway on pulmonary small arteries isolated from HP/LF and HP/HF territories were further investigated. There were no differences in the in vivo pulmonary vasodilator response to SNP and the pulmonary vasoconstrictor response to endothelial nitric oxide synthase (eNOS) inhibition up to 8 weeks after PVB as compared to the sham group. However, at 10 and 12 weeks post-PVB, the in vivo pulmonary vasodilation in response to SNP was larger in the PVB group. Similarly, the vasoconstriction to eNOS inhibition was larger in the PVB group, particularly during exercise, while pulmonary vasodilation in response to PDE5 inhibition was larger in the PVB group both at rest and during exercise. In isolated pulmonary small arteries, sensitivity to NO donor SNP was similar in PVB vs. sham groups irrespective of HP/LF and HP/HF, while sensitivity to the PDE5 inhibitor sildenafil was lower in PVB HP/HF and sensitivity to bradykinin was lower in PVB HP/LF. In conclusion, both NO availability and sensitivity were increased in the PVB group. The increased nitric oxide sensitivity was not the result of a decreased PDE5 activity, as PDE5 activity was even increased. Some vasodilators differentially effect HP/HF vs. HP/LF vasculature.

Relationship between pulmonary hypertension and outcomes among patients with heart failure with reduced ejection fraction

Objectives: To identify predictors of pulmonary hypertension (PHT) and the predictive value of PHT for rehospitalization among patients with heart failure with reduced ejection fraction (HFrEF). Methods: A retrospective study of 351 hospitalized patients with heart failure (HF). Patients 18 years and above with HFrEF secondary to non-ischemic cardiomyopathy were reviewed. Patients with coronary artery disease, preserved ejection fraction and other secondary causes of PHT apart from HF were excluded. PHT as a predictor of 30-day and six-month re-admission was assessed as well as important possible predictors of PHT. Cox regression analysis, multiple linear regression as well as other statistical tools were employed as deemed appropriate. Results: Thirty-seven (37) and 99 patients were re-hospitalized within 30 days and 6 months after discharge for decompensated HF, respectively. After Cox regression analysis, higher hemoglobin reduced the odds of rehospitalization for decompensated HF (p = 0.015) within 30 days after discharge while higher pulmonary artery systolic pressure (PASP) (p = 0.002) and blood urea nitrogen (BUN) (p = 0.041) increased the odds of rehospitalization within 6 months of discharge. The predictors of the PHT among patients with HFrEF after multiple linear regression were low BMI (p = 0.027), increasing age (p = 0.006) and increased left atrial diameter (LAD) on echocardiography (p = 0.0001). Conclusion: Patients with HFrEF have a high predisposition to developing PHT if at admission, they have low BMI, dilated left atrium or are older. Patients with one or more of these attributes may need more intensive therapy to reduce the risk of developing PHT and in turn reduce readmission rates.

Pulmonary vascular mechanical consequences of ischemic heart failure and implications for right ventricular function

Left heart failure (LHF) is the most common cause of pulmonary hypertension, which confers an increase in morbidity and mortality in this context. Pulmonary vascular resistance has prognostic value in LHF, but otherwise the mechanical consequences of LHF for the pulmonary vasculature and right ventricle (RV) remain unknown. We sought to investigate mechanical mechanisms of pulmonary vascular and RV dysfunction in a rodent model of LHF to address the knowledge gaps in understanding disease pathophysiology. LHF was created using a left anterior descending artery ligation to cause myocardial infarction (MI) in mice. Sham animals underwent thoracotomy alone. Echocardiography demonstrated increased left ventricle (LV) volumes and decreased ejection fraction at 4 wk post-MI that did not normalize by 12 wk post-MI. Elevation of LV diastolic pressure and RV systolic pressure at 12 wk post-MI demonstrated pulmonary hypertension (PH) due to LHF. There was increased pulmonary arterial elastance and pulmonary vascular resistance associated with perivascular fibrosis without other remodeling. There was also RV contractile dysfunction with a 35% decrease in RV end-systolic elastance and 66% decrease in ventricular-vascular coupling. In this model of PH due to LHF with reduced ejection fraction, pulmonary fibrosis contributes to increased RV afterload, and loss of RV contractility contributes to RV dysfunction. These are key pathologic features of human PH secondary to LHF. In the future, novel therapeutic strategies aimed at preventing pulmonary vascular mechanical changes and RV dysfunction in the context of LHF can be tested using this model. NEW & NOTEWORTHY In this study, we investigate the mechanical consequences of left heart failure with reduced ejection fraction for the pulmonary vasculature and right ventricle. Using comprehensive functional analyses of the cardiopulmonary system in vivo and ex vivo, we demonstrate that pulmonary fibrosis contributes to increased RV afterload and loss of RV contractility contributes to RV dysfunction. Thus this model recapitulates key pathologic features of human pulmonary hypertension-left heart failure and offers a robust platform for future investigations.

Transition from post-capillary pulmonary hypertension to combined pre- and post-capillary pulmonary hypertension in swine: a key role for endothelin

Key points

Passive, isolated post‐capillary pulmonary hypertension (PH) secondary to left heart disease may progress to combined pre‐ and post‐capillary or ‘active’ PH

This ‘activation’ of post‐capillary PH significantly increases morbidity and mortality, and is still incompletely understood.

In this study, pulmonary vein banding gradually produced post‐capillary PH with structural and functional microvascular remodelling in swine.

Ten weeks after banding, the pulmonary endothelin pathway was upregulated, likely contributing to pre‐capillary aspects in the initially isolated post‐capillary PH.

Inhibition of the endothelin pathway could potentially stop the progression of early stage post‐capillary PH.

Abstract

Passive, isolated post‐capillary pulmonary hypertension (IpcPH) secondary to left heart disease may progress to combined pre‐ and post‐capillary or ‘active’ PH (CpcPH) characterized by chronic pulmonary vascular constriction and remodelling. The mechanisms underlying this ‘activation’ of passive pulmonary hypertension (PH) remain incompletely understood. Here we investigated the role of the vasoconstrictor endothelin‐1 (ET) in the progression from IpcPH to CpcPH in a swine model for post‐capillary PH. Swine underwent pulmonary vein banding (PVB; n = 7) or sham‐surgery (Sham; n = 6) and were chronically instrumented 4 weeks later. Haemodynamics were assessed for 8 weeks, at rest and during exercise, before and after administration of the ET receptor antagonist tezosentan. After sacrifice, the pulmonary vasculature was investigated by histology, RT‐qPCR and myograph experiments. Pulmonary arterial pressure and resistance increased significantly over time. mRNA expression of prepro‐endothelin‐1 and endothelin converting enzyme‐1 in the lung was increased, while ET_A expression was unchanged and ET_B expression was downregulated. This was associated with increased plasma ET levels from week 10 onward and a more pronounced vasodilatation to in vivo administration of tezosentan at rest and during exercise. Myograph experiments showed decreased endothelium‐dependent vasodilatation to Substance P and increased vasoconstriction to KCl in PVB swine consistent with increased muscularization observed with histology. Moreover, maximal vasoconstriction to ET was increased whereas ET sensitivity was decreased. In conclusion, PVB swine gradually developed PH with structural and functional vascular remodelling. From week 10 onward, the pulmonary ET pathway was upregulated, likely contributing to pre‐capillary activation of the initially isolated post‐capillary PH. Inhibition of the ET pathway could thus potentially provide a pharmacotherapeutic target for early stage post‐capillary PH.

Passive, isolated post‐capillary pulmonary hypertension (PH) secondary to left heart disease may progress to combined pre‐ and post‐capillary or ‘active’ PH

This ‘activation’ of post‐capillary PH significantly increases morbidity and mortality, and is still incompletely understood.

In this study, pulmonary vein banding gradually produced post‐capillary PH with structural and functional microvascular remodelling in swine.

Ten weeks after banding, the pulmonary endothelin pathway was upregulated, likely contributing to pre‐capillary aspects in the initially isolated post‐capillary PH.

Inhibition of the endothelin pathway could potentially stop the progression of early stage post‐capillary PH.

Angiogenic and inflammatory biomarkers in the differentiation of pulmonary hypertension

OBJECTIVES

Pulmonary hypertension (PH) is a serious condition where diagnosis often is delayed due to unspecific symptoms. New methods to diagnose and differentiate PH earlier would therefore be of great value. The aim of this study was therefore to evaluate the relationship between circulating angiogenic and inflammatory biomarkers and various hemodynamic variables in relation to different causes of PH.

DESIGN

Plasma samples from 63 patients at diagnosis were extracted from Lund Cardio Pulmonary Register, separated into pulmonary arterial hypertension (PAH, n = 22), chronic thromboembolic pulmonary hypertension (CTEPH, n = 15) and left heart disease (LHD) with (n = 21) and without (n = 5) PH. Blood samples from eight control subjects devoid of PH were additionally evaluated. Plasma concentrations of angiogenic (PlGF, Tie2, VEGF-A, VEGF-D, bFGF, sFlt-1) and inflammatory (IL-6, IL-8, TNF-α) biomarkers were analysed and related to hemodynamic variables.

RESULTS

SFlt-1 (p < .004) and VEGF-A (p < .035) were higher in all PH groups compared to controls. TNF-α (p < .030) were elevated in PAH patients in relation to the other PH groups as well as controls. Likewise, plasma VEGF-D (p < .008) were elevated in LHD with PH compared to the other groups with PH and controls. In PAH, higher sFlt-1 concentrations correlated to a worse state of hemodynamics.

CONCLUSIONS

Our findings indicate that sFlt-1 and VEGF-A may be future tools when discriminating PH from non-PH. Moreover, TNF-α may differentiate PAH and VEGF- D may differentiate LHD with PH, from the other groups with PH, as well as controls. SFlt-1 may furthermore play a role as a future marker of disease severity.

Intratracheal administration of isosorbide dinitrate improves pulmonary artery pressure and ventricular remodeling in a rat model of heart failure following myocardial infarction

Pulmonary hypertension due to left heart disease is associated with poor outcomes. This study investigated the beneficial effects of isosorbide dinitrate (ISDN) inhalation on pulmonary pressure and ventricular remodeling in a rat model of heart failure (HF) following myocardial infarction (MI). To assess the effect of ISDN on pulmonary pressure, 20 male Sprague-Dawley (SD) rats were randomized to four groups: Normal saline (NS) 1 ml/kg, ISDN 1 mg/kg, NS 3 ml/kg or ISDN 3 mg/kg following coronary ligation. Assessments included pulmonary and systemic artery pressure alterations, lung weight/body weight and plasma nitric oxide (NO) concentration. To assess the effect of ISDN on ventricular remodeling, 30 SD rats were randomized to three groups: Sham surgery, MI-NS (intratracheal NS 3 ml/kg for 13 days following coronary ligation), and MI-ISDN (intratracheal ISDN 3 mg/kg for 13 days following coronary ligation). On day 15, all rats underwent echocardiogram and hemodynamic assessments. The area affected by MI was evaluated using microscopy and vascular endothelial growth factor (VEGF) expression was examined using immunohistochemistry. Plasma epinephrine, norepinephrine and brain natriuretic peptide (BNP) levels were assessed by ELISA. Intratracheal ISDN reduced pulmonary and systematic artery pressure without pulmonary edema when compared with NS. The reduction was associated with increased plasma NO levels. ISDN inhalation for 14 days reduced MI size and alleviated left and right ventricular remodeling following MI. These hemodynamic and morphological improvements were associated with decreased plasma epinephrine, norepinephrine and BNP levels, and an increased VEGF positive area at the border of MI region. In conclusion, intratracheal administration of ISDN was effective in improving ventricular remodeling and cardiac function in a rat model of HF following MI.

Impact of postoperative pulmonary hypertension on outcome after heart transplantation

OBJECTIVES

We wanted to investigate the effects of postoperative pulmonary hypertension (PH_postop: mean pulmonary artery pressure [MPAP] ≥ 25 mmHg), diastolic pressure gradient (DPG), pulmonary vascular resistance (PVR), and repeated hemodynamic measurements on long-term survival after heart transplantation (HT).

DESIGN

Eighty-nine patients who underwent HT at Skåne University Hospital in Lund in the period 1988-2010 and who were evaluated with right-heart-catheterization at rest, prior to HT and repeatedly during the first postoperative year, were grouped based on their MPAP, DPG, and PVR.

RESULTS

One year after HT, survival was lower in patients with PH_postop than in those without, in patients with DPG ≥7 mmHg than in those with DPG <7 mmHg, and in patients with PVR >3 WU than in those with PVR ≤3 WU. Moreover, compared to patients with no PH_postop or with PH_postop at one evaluation during the first year after HT, PH_postop at repeated evaluations was associated with higher mortality (hazard ratio 3.4, 95% CI 1.4-8.0). There was no significant difference in acute cellular rejection between patients with and without PH_postop, but postoperative kidney function was worse in patients with repeated PH_postop.

CONCLUSIONS

When defined according to present guidelines, PH one year after HT may emerge as a prognostic marker for long-term outcome after HT. Moreover, PH_postop at repeated evaluations during the first year after HT had stronger prognostic value than PH_postop at a single examination, illustrating a means of identifying a high-risk population. However, confirmation in larger multi-center studies is warranted.

Risk factors for pulmonary hypertension in patients receiving maintenance peritoneal dialysis

We investigated the risk factors for pulmonary hypertension (PH) in patients receiving maintenance peritoneal dialysis (MPD). A group of 180 end-stage renal disease patients (124 men and 56 women; mean age: 56.43±8.36) were enrolled in our study, which was conducted between January 2009 and June 2014. All of the patients received MPD treatment in the Dialysis Center of the Second Affiliated Hospital of Soochow University. Clinical data, laboratory indices, and echocardiographic data from these patients were collected, and follow-ups were scheduled bi-monthly. The incidence and relevant risk factors of PH were analyzed. The differences in measurement data were compared by t-test and enumeration data were compared with the χ2 test. Among the 180 patients receiving MPD, 60 were diagnosed with PH. The remaining 120 were regarded as the non-PH group. Significant differences were observed in the clinical data, laboratory indices, and echocardiographic data between the PH and non-PH patients (all P<0.05). Furthermore, hypertensive nephropathy patients on MPD showed a significantly higher incidence of PH compared with non-hypertensive nephropathy patients (P<0.05). Logistic regression analysis showed that the proportion of internal arteriovenous fistula, C-reactive protein levels, and ejection fraction were the highest risk factors for PH in patients receiving MPD. Our study shows that there is a high incidence of PH in patients receiving MPD and hypertensive nephropathy patients have an increased susceptibility to PH.

Hemodynamic Characteristics Including Pulmonary Hypertension at Rest and During Exercise Before and After Heart Transplantation

Background

Little is known about the hemodynamic response to exercise in heart failure patients at various ages before and after heart transplantation (HT). This information is important because postoperative hemodynamics may be a predictor of survival. To investigate the hemodynamic response to HT and exercise, we grouped our patients based on preoperative age and examined their hemodynamics at rest and during exercise before and after HT.

Methods and Results

Ninety-four patients were evaluated at rest prior to HT with right heart catheterization at our laboratory. Of these patients, 32 were evaluated during slight supine exercise before and 1 year after HT. Postoperative evaluations were performed at rest 1 week after HT and at rest and during exercise at 4 weeks, 3 months, 6 months, and 1 year after HT. The exercise patients were divided into 2 groups based on preoperative age of ≤50 or >50 years. There were no age-dependent differences in the preoperative hemodynamic exercise responses. Hemodynamics markedly improved at rest and during exercise at 1 and 4 weeks, respectively, after HT; however, pulmonary and, in particular, ventricular filling pressures remained high during exercise at 1 year after HT, resulting in normalized pulmonary vascular resistance response but deranged total pulmonary vascular resistance response.

Conclusions

Our findings suggest that, (1) in patients with heart failure age ≤50 or >50 years may not affect the hemodynamic response to exercise to the same extent as in healthy persons, and (2) total pulmonary vascular resistance may be more adequate than pulmonary vascular resistance for evaluating the exercise response after HT.