Chronic Thromboembolic Pulmonary Hypertension

Platelets Are Highly Activated in Patients of Chronic Thromboembolic Pulmonary Hypertension

Objective—

Chronic thromboembolic pulmonary hypertension (CTEPH) is a fatal disease that is distinct from pulmonary arterial hypertension (PAH). Although CTEPH is characterized by obstruction of major pulmonary artery because of chronic thrombus, it remains unclear whether CTEPH is associated with prothrombotic condition.

Approach and Results—

In addition to conventional markers, GTP-bound levels of Rap1, RhoA, RalA, Rac1, and Ras in platelets, which are implicated for platelet activation, were measured in patients without pulmonary hypertension (non-PH, n=15), patients with PAH (n=19), and patients with CTEPH (n=25). Furthermore, the responsiveness to ex vivo thrombin stimulation was also evaluated. The ratios of the P-selectin positive platelets in the non-PH patients, patients with PAH, and patients with CTEPH were 1.40% (median and interquartile range, 0.83–1.82), 2.40% (1.80–3.39), and 2.63% (1.90–8.22), respectively (non-PH versus CTEPH, P <0.01). The activated GPIIb/IIIa-positive platelets were 6.01% (1.34–7.87), 11.39% (5.69–20.86), and 9.74% (7.83–24.01), respectively (non-PH versus CTEPH, P =0.01). GTP-bound RhoA was 1.79% (0.94–2.83), 4.03% (2.01–5.14), and 2.01% (1.22–2.48), respectively (non-PH versus PAH, P =0.04), and GTP-bound RalA was 1.58% (1.08–2.11), 3.02% (2.03–3.54), and 2.64% (1.42–4.28), respectively (non-PH versus PAH, P =0.023; non-PH versus CTEPH, P =0.048). In contrast, Rac1, Rap1, or Ras was not activated in any groups. The platelets of patients with CTEPH exhibited hyperresponsiveness to ex vivo thrombin stimulation compared with those of non-PH patients when evaluated for the surface markers. Either D-dimer or fibrin degradation product level was not increased in patients with CTEPH.

Conclusions—

These results provide the first direct evidence that platelets of patients with CTEPH are highly activated and exhibit hyperresponsiveness to thrombin stimulation.

The role of phosphodiesterase inhibitors in the management of pulmonary vascular diseases

Phosphodiesterase inhibitors (PDE) can be used as therapeutic agents for various diseases such as dementia, depression, schizophrenia and erectile dysfunction in men, as well as congestive heart failure, chronic obstructive pulmonary disease, rheumatoid arthritis, other inflammatory diseases, diabetes and various other conditions. In this review we will concentrate on one type of PDE, mainly PDE5 and its role in pulmonary vascular diseases.

Pulmonary hypertension in systemic lupus erythematosus: pulmonary thromboembolism is the leading cause

BACKGROUND

Pulmonary hypertension (PH) is a life-threatening complication of systemic lupus erythematosus (SLE). Pulmonary hypertension in SLE has a variety of causes. Diagnosing early and defining the cause of PH accurately can provide better clinical outcome in SLE. We investigated the causes and characteristics of PH in patients with SLE.

METHODS

One hundred twenty-one patients with SLE who had a visit in a 6-month period were assessed retrospectively. Patients who ever had a systolic pulmonary arterial pressure of 40 mm Hg or greater by Doppler echocardiography were considered to have PH.

RESULTS

Among 122 patients, 65 had echocardiography for some reason, and 10 (8.2%) were diagnosed as having PH by echocardiographic examination. This number reduced to 9 (7.4%) when we excluded the patient with normal pulmonary artery pressure at right heart catheterization. Causes of PH were as follows: thromboembolic events in 4 patients (44.4%) (2 of them had chronic thromboembolic PH), left-sided heart disease in 2 patients (22.2%), pulmonary arterial hypertension in 1 patient (11.1%), high cardiac output state in 1 patient (11.1%), and transient elevation of systolic pulmonary artery pressure in 1 patient (11.1%) who had a history of venous thromboembolism. Venous thromboembolic disease was significantly higher in patients with SLE with PH in comparison to patients with SLE without PH (7 patients [6.3%] vs 5 patients [50.0%]; P = 0.001). All patients improved clinically during their short-term follow-up.

CONCLUSIONS

Patients with SLE are at increased risk for PH. This study highlights the complexity of the differential diagnosis of PH in patients with SLE once again and emphasizes the importance of pulmonary thromboembolism as a cause of PH. One should investigate patients with SLE with unexplained symptoms and/or signs related to PH for possible treatable causes.

An improved technique for pulmonary endarterectomy

We report a modified technique for pulmonary endarterectomy (PEA) on a 67-year-old man with chronic thromboembolic pulmonary hypertension (CTEPH) who presented with dyspnea. He was referred to our medical center for coronary artery bypass grafting. CTEPH had not been detected in his first visit to another medical center, but upon re-evaluation, the diagnosis was confirmed. PEA was performed with a modified method, which seems to be safe and suitable for the removal of clot and fibrotic materials. Iatrogenic dissection was performed with normal saline injection in the pulmonary artery, and then, the clot was removed completely. Although the technique may not be applicable for all cases, it can be used as an alternative to using an aspirating dissector and a pair of forceps.

Chronic thromboembolic pulmonary hypertension: do not miss the chance for an early diagnosis

BACKGROUND

Chronic thromboembolic pulmonary hypertension most often results from obstruction of the pulmonary vascular bed by nonresolving thromboemboli. Misdiagnosis of the disease is common because patients often present with subtle or nonspecific symptoms. Furthermore, some features in chest imaging may mimic parenchymal lung disease. The most clinically important mimic in high-resolution chest tomography is air trapping, which can be seen in a variety of small airway diseases.

CASE REPORT

We present the case of a 45-year-old woman with a long history of dyspnea and exercise intolerance, misdiagnosed with allergic alveolitis. The diagnosis of CTEPH was finally established with computed tomography (CT) angiography and hemodynamics.

CONCLUSIONS

Chronic thromboembolism is under-diagnosed and also frequently misdiagnosed in clinical practice. The present report aims to increase the awareness of clinicians towards an accurate diagnosis of the disease, which is necessary for the early referral of CTEPH patients for operability.

Microvascular disease in chronic thromboembolic pulmonary hypertension: a role for pulmonary veins and systemic vasculature

Limited numbers of operated patients with chronic thromboembolic pulmonary hypertension (CTEPH) are refractory to pulmonary endarterectomy (PEA) and experience persistent pulmonary hypertension (PH).

We retrospectively assessed lung histology available from nine patients with persistent PH (ineffective PEA (inPEA) group) and from eight patients transplanted for distal CTEPH inaccessible by PEA (noPEA group). Microscopically observed peculiarities were compared with the histology of a recently developed CTEPH model in piglets. Pre-interventional clinical/haemodynamic data and medical history of patients from the inPEA and noPEA groups were collected and analysed.

Conspicuous remodelling of small pulmonary arteries/arterioles, septal veins and pre-septal venules, including focal capillary haemangiomatosis, as well as pronounced hypertrophy and enlargement of bronchial systemic vessels, were the predominant pattern in histology from both groups. Most findings were reproduced in our porcine CTEPH model. Ink injection experiments unmasked abundant venular involvement in so-called small vessel or microvascular disease, as well as post-capillary bronchopulmonary shunting in human and experimental CTEPH.

Microvascular disease is partly due to post-capillary remodelling in human and experimental CTEPH and appears to be related to bronchial-to-pulmonary venous shunting. Further studies are needed to clinically assess the functional importance of this finding.

Saudi Guidelines on the Diagnosis and Treatment of Pulmonary Hypertension: Chronic thromboembolic pulmonary hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is categorized as group IV in the WHO classification for pulmonary hypertension. The disease requires a very low index of suspicion for identification and needs a special diagnostic approach utilizing clinical, radiological, and hemodynamic tools. As CTEPH is potentially curable, all efforts should be consumed to reach the accurate diagnosis and subsequently evaluated for operability.

Although pulmonary endarterectomy (PEA) is the only curative tool so far, recent updates concerning medical and interventional therapy have made significant advances in inoperable patients.

In this review, we provide a detailed discussion on diagnostic algorithm, surgical operability criteria, PEA, and the medical therapy.

Saudi guidelines on the diagnosis and treatment of pulmonary hypertension: 2014 updates

The Saudi Association for Pulmonary Hypertension (previously called Saudi Advisory Group for Pulmonary Hypertension) has published the first Saudi Guidelines on Diagnosis and Treatment of Pulmonary Arterial Hypertension back in 2008.[1] That guideline was very detailed and extensive and reviewed most aspects of pulmonary hypertension (PH). One of the disadvantages of such detailed guidelines is the difficulty that some of the readers who just want to get a quick guidance or looking for a specific piece of information might face.

All efforts were made to develop this guideline in an easy-to-read form, making it very handy and helpful to clinicians dealing with PH patients to select the best management strategies for the typical patient suffering from a specific condition. This Guideline was designed to provide recommendations for problems frequently encountered by practicing clinicians involved in management of PH. This publication targets mainly adult and pediatric PH-treating physicians, but can also be used by other physicians interested in PH.

Piglet model of chronic pulmonary hypertension

None of the animal models have been able to reproduce all aspects of CTEPH because of the rapid resolution of the thrombi in the pulmonary vasculature. The aim of this study was to develop an easily reproducible large-animal model of chronic pulmonary hypertension (PH) related to the development of a postobstructive and overflow vasculopathy. Chronic PH was induced in 5 piglets by ligation of the left pulmonary artery (PA) through a midline sternotomy followed by weekly transcatheter embolization of the right lower-lobe arteries. Sham-operated piglets (n = 5) served as controls. Hemodynamics, RV function, lung morphometry, and endothelin-1 (ET-1) pathway gene expression (ET-1 and its receptors ETA and ETB) were assessed after 5 weeks in the obstructed (left lung and right lower lobe) and unobstructed (right upper lobe) territories. All animals developed chronic PH within 5 weeks. Compared to controls, chronic-PH animals had higher mean PA pressure (28.5 ± 1.7 vs. 11.6 ± 1.8 mmHg, P = 0.0001) and total pulmonary resistance (784 ± 160 vs. 378 ± 51 dyn s(-1) cm(-5), P = 0.05). Echocardiography showed RV enlargement, RV wall thickening (56 ± 5 vs. 30 ± 4 mm, P = 0.0003), decreased tricuspid annular plane systolic excursion (11.3 ± 0.9 vs. 14.4 ± 0.4 mm, P = 0.01), and paradoxical septal motion. In obstructed territories, morphometry demonstrated increases in the number of bronchial arteries per bronchus (8.7 ± 0.9 vs. 2 ± 0.17, P < 0.0001) and in distal PA media thickness (60% ± 2.8% vs. 29% ± 0.9%, P < 0.0001), consistent with postobstructive vasculopathy. Distal PA media thickness was increased in unobstructed territories (70% ± 2.4% vs. 29% ± 0.9%, P < 0.0001). ET-1 was overexpressed in unobstructed territories, compared to controls and obstructed territories. In conclusion, the large-animal model described here is reproducible and led to the development of PH in a relatively short time frame.

Cardiopulmonary exercise testing suggests a beneficial response to pulmonary endarterectomy in a patient with chronic thromboembolic obstruction and normal preoperative pulmonary hemodynamics

Pulmonary endarterectomy offers a symptomatic and survival benefit in patients with chronic thromboembolic pulmonary hypertension through sustained improvement in right ventricular function. However, its role in patients with symptom limitation, chronic thrombotic obstruction, and a normal pulmonary hemodynamic profile is less clear. Cardiopulmonary exercise testing (CPET) stresses the cardiopulmonary system and has a characteristic response in pulmonary hypertension. CPET may therefore reveal abnormalities in patients with chronic thrombotic obstruction where hemodynamic investigations conducted at rest are reassuring. Using incremental CPET, we demonstrated improvements in right ventricular performance and ventilatory efficiency following pulmonary endarterecomy in a patient with preoperative exercise limitation and normal pulmonary hemodynamics. Careful evaluation of exercise responses may extend the potential benefit offered by pulmonary endarterectomy in patients with chronic thromboembolic obstruction irrespective of their resting hemodynamic profile.

The Use of Echocardiography in Diagnosis, Risk Stratification and Management of Pulmonary Embolism: A Retrospective Single-Centre Analysis

Pulmonary embolism (PE) is a life-threatening condition with high morbidity and mortality. The presence of systolic hypotension and/or right heart strain (RHS) is currently used to stratify patients and direct management. Echocardiography has a demonstrated role in the management of PE and has been used to guide therapies such as thrombolysis. We performed a retrospective study of all patients admitted to the Nepean Hospital Intensive Care Unit (ICU) with a diagnosis of acute pulmonary embolism between 1 January 2006 and 31 December 2011 to analyse if and how echocardiography was used in the diagnosis, classification and management of these patients. During this time, 59 patients were admitted with a diagnosis of acute PE or developed a PE in the intensive care unit, of whom 22 had a diagnosis of submassive PE, demonstrating RHS on echocardiography. Eleven of these patients received thrombolysis and survived to hospital discharge. The use of echocardiography identified greater numbers of patients with high risk pulmonary embolus, enabling risk stratification for thrombolysis with potential morbidity and mortality benefit.

Chronic thromboembolic pulmonary hypertension: Medical treatment

Chronic thromboembolic pulmonary hypertension (CTEPH) is responsible for significant levels of morbidity and mortality. The estimated cumulative incidence of CTEPH is 2-4% among patients presenting with acute pulmonary thromboembolism. Currently, at the time of CTEPH diagnosis, 37.9% of the patients in an international registry were receiving at least one pulmonary arterial hypertension (PAH)-targeted therapy. Advanced medical therapy is considered in patients with inoperable disease, as a bridge to pulmonary endarterectomy or in those with persistent or recurrent pulmonary hypertension. PAH-specific medical therapies include endothelin receptor antagonists, phosphodiesterase inhibitors, and prostacyclin analogues. The present article will focus on recent developments in the pharmacological treatment of CTEPH.

Safety and efficacy of percutaneous transluminal pulmonary angioplasty in elderly patients

BACKGROUND

Percutaneous transluminal pulmonary angioplasty (PTPA) is a recently developed catheter-based therapy for chronic thromboembolic pulmonary hypertension (CTEPH). The aim of the present study was to investigate the safety and efficacy of PTPA in elderly patients with CTEPH.

METHODS

In all, 257 PTPA sessions in 70 patients (median age 63 years) were analyzed. Patients were divided into two groups according to age: (i) a younger group (<65 years; n=39); and (ii) an elderly group (≥65 years; n=31).

RESULTS

Hemodynamic improvements were comparable between the younger and elderly groups (63.1% vs. 68.2% decrease in pulmonary vascular resistance, respectively; P>0.05). The median length of stay in the intensive care unit after each session (1.0 vs. 1.0 days) and in hospital per session (9.2 vs. 9.4 days) was similar between the two groups (P>0.05 for all). The prevalence of reperfusion pulmonary edema (23.4% vs. 26.3% across all sessions) and other complications, such as contrast dye-induced nephropathy (0% vs. 2.0%), infection (0% vs. 0%), and neurological complications (0% vs. 1.0%), was comparable in the younger vs. elderly groups (P>0.05 for all). One-year all-cause mortality was similar in the younger and elderly groups (0% vs. 3.2%, respectively; P>0.05).

CONCLUSIONS

PTPA can be performed safely and effectively, even in elderly patients, and could be considered as an alternative therapeutic strategy for elderly patients who are too fragile for pulmonary endarterectomy (PEA) or who are treated in institutions without highly experienced PEA surgeons.

Organized thrombus in pulmonary arteries in patients with chronic thromboembolic pulmonary hypertension; imaging with cone beam computed tomography

PURPOSE

To assess the usefulness of cone-beam CT (CBCT) during pulmonary angiography for the evaluation of organized thrombus at segmental or subsegmental arteries in patients with chronic thromboembolic pulmonary hypertension (CTEPH).

MATERIALS AND METHODS

The segmental and/or subsegmental pulmonary arteries of 13 patients with CTEPH were evaluated by CBCT. We classified representative forms of organized thrombus into 4 types (type 1: webs, type 2: web and slits, type 3: slits, and type 4: narrowing or complete occlusion), and the distribution and frequency of the organized thrombus were evaluated. The relative detectability of these lesions using CBCT was compared with that in contrast-enhanced CT pulmonary angiography (CTPA).

RESULTS

Type 1 lesions were most frequently observed in both segmental (30/65 = 46 %) and subsegmental branches (72/156 = 46 %). Type 2 lesions were relatively less frequent than type 1, but subsegmental branches were frequently involved (29/156 = 19 %). Type 3 lesions observed as a thin flap in 9/156 subsegmental branches (6 %). Comparing with CTPA, all 40 lesions in segmental branches were detectable in CTPA, whereas only 62 lesions among 90 lesions (69 %) in subsegmental branches could be observed by CTPA.

CONCLUSION

CBCT is found to be useful for the treatment planning of balloon pulmonary angioplasty distal to segmental arteries.

BMPR2 germline mutation in chronic thromboembolic pulmonary hypertension

INTRODUCTION

Heterozygous germline mutations of the bone morphogenetic protein type II receptor (BMPR2) gene BMPR2 are the most important predisposing factors for heritable pulmonary arterial hypertension. BMPR2 mutation was occasionally reported in pulmonary veno-occlusive disease, appetite suppressant-related pulmonary arterial hypertension (PAH), and PAH with congenital heart disease.

MATERIALS AND METHODS

In this study we identified a missense mutation (c.2296A > G) located in BMPR2 exon 12 in a patient with chronic thromboembolic pulmonary hypertension (CTEPH).

CONCLUSION

It is the first report of a BMPR2 mutation in CTEPH. Our study provides innovative insight into etiology of CTEPH. The genetic predisposing factor is an important component in the process of this CTEPH patient.

A new era of therapeutic strategies for chronic thromboembolic pulmonary hypertension by two different interventional therapies; pulmonary endarterectomy and percutaneous transluminal pulmonary angioplasty

BACKGROUND

Pulmonary endarterectomy (PEA) is established for the treatment of chronic thromboembolic pulmonary hypertension (CTEPH). Recently, percutaneous transluminal pulmonary angioplasty (PTPA) has been added for peripheral-type CTEPH, whose lesions exist in segmental, subsegmental, and more distal pulmonary arteries. A shift in clinical practice of interventional therapies occurred in 2009 (first mainly PEA, later PTPA). We examined the latest clinical outcomes of patients with CTEPH.

METHODS AND RESULTS

This study retrospectively included 136 patients with CTEPH. Twenty-nine were treated only with drug (Drug-group), and the other 107 underwent interventional therapies (Interventions-group) (39 underwent PEA [PEA-group] and 68 underwent PTPA [PTPA-group]). Total 213 PTPA sessions (failures, 0%; mortality rate, 1.47%) was performed in the PTPA-group (complications: reperfusion pulmonary edema, 7.0%; hemosputum or hemoptysis, 5.6%; vessel dissection, 2.3%; wiring perforation, 0.9%). Although baseline hemodynamic parameters were significantly more severe in the Interventions-group, the outcome after the diagnosis was much better in the Interventions-group than in the Drug-group (98% vs. 64% 5-year survival, p<0.0001). Hemodynamic improvement in the PEA-group was a 46% decrease in mean pulmonary arterial pressure (PAP) and a 49% decrease in total pulmonary resistance (TPR) (follow-up period; 74.7 ± 32.3 months), while those in the PTPA-group were a 40% decrease in mean PAP and a 49% decrease in TPR (follow-up period; 17.4 ± 9.3 months). The 2-year survival rate in the Drug-group was 82.0%, and the 2-year survival rate, occurrence of right heart failure, and re-vascularization rate in the PEA-group were 97.4%, 2.6%, and 2.8%, and those in the PTPA-group were 98.5%, 2.9%, and 2.9%, respectively.

CONCLUSION

The patients who underwent interventional therapies had better results than those treated only with drugs. The availability of both of these operative and catheter-based interventional therapies leads us to expect the dawn of a new era of therapeutic strategies for CTEPH.

Hemodynamic and symptomatic improvement after delayed thrombolysis with Reteplase in a patient with massive bilateral pulmonary emboli

Most patients surviving the acute phase of pulmonary embolism will recover with no residue. But, 2-4% of patients will progress to chronic thromboembolic pulmonary hypertension. In this group, usually a 'Honey moon' period is seen but a few may show progression with ongoing symptoms despite medical treatment. In this case report, we review a patient in whom delayed thrombolytic therapy was administered due to progressive symptoms after 21 days. Her condition was stabilized. The early posttreatment computed tomographic pulmonary angiography (CTPA) showed incomplete resolution, but after 6 months she was functional class I with a normal CTPA and echocardiography.

Recombinant tissue plasminogen activator plus heparin compared with heparin alone for patients with acute submassive pulmonary embolism: one-year outcome

Objective

To evaluate the long-term effects of thrombolysis on patients with submassive pulmonary embolism (PE).

Methods

Data of 136 patients with acute submassive PE and low risk of bleeding were prospectively collected from January 2005 to October 2011 in a single medical center. Patients received recombinant tissue plasminogen activator (r-tPA) plus low molecular weight heparin (LMWH, TT group, n = 79) or LMWH alone (AT group, n = 57), depending on treating physician's recommendation and patient's preference. Echocardiography was performed at admission, 24 h, 6 and 12 months to evaluate right ventricular function. Computed tomography pulmonary angiography (CTPA) and lung perfusion scan were performed on admission, at 7 days, 6 and 12 months to evaluate clot burden.

Results

Seventy-nine patients received r-tPA plus LMWH (TT group) while 57 received LMWH alone (AT group). The baseline characteristics and risk factors did not differ between the two groups. Respiratory rate, heart rate, and systolic blood pressure improved within two hours in both groups. Systolic pulmonary arterial pressure and tricuspid regurgitation improved to a greater extent in the TT group at 24 h, and at 12 months (P < 0.001), as compared to those in the AT group. At one week, and 12 months, clot burden decreased more in AT group, as compared to that in AT group (P < 0.001). There was no death due to bleeding in both groups. Recurrent PE were similar in both groups (2.5% in TT vs. 1.8% in AT). The rates of minor hemorrhages were 6.3% in TT group and 1.8% in AT group (P < 0.05).

Conclusion

In submassive PE patient who has low risk of bleeding, thrombolysis plus anticoagulation can lead to greater improvement of right ventricular dysfunction and clot burden reduction as compared to anticoagulation therapy alone.

Pulmonary endarterectomy - an example of treatment of right ventricular after load failure

The treatment of choice for patients with chronic thromboembolic pulmonary hypertension is pulmonary endarterectomy to reduce pulmonary vascular resistance with significant symptomatic and prognostic benefit. The fundamental aim of the surgery is to perform a full endarterectomy (not embolectomy or thrombectomy) in both pulmonary arteries. The operation is performed via a median sternotomy with hypothermic cardiopulmonary bypass (CPB) at 20 °C. Pulmonary arteriotomies are performed within the pericardium and periods of circulatory arrest are necessary to reduce collateral blood flow from bronchial arteries and allow a clear field for dissection distally. The endarterectomy plane is raised carefully as it is essential the correct layer be identified. The dissection proceeds within the superficial media into all the affected segmental and sub-segmental vessels. A cast of the inner layer of the pulmonary arterial tree is then dissected free by eversion moving towards the periphery. After completion of the endarterectomies, and the patient is rewarmed slowly on full CPB. During weaning from CPB the right-sided filling pressures should be kept low, guided by invasive haemodynamic monitoring. Survival to hospital discharge is ≫95% in experienced centres with outcome dependent on the disease pattern and pulmonary vascular resistance pre- and post-surgery.

Dynamic blood flow and wall shear stress in pulmonary hypertensive disease

This study provides new model of pulsatile flow in the pulmonary circulation in health and pulmonary hypertensive disease. Structural vascular remodeling typical of pulmonary hypertensive disease was implemented in the model by progressively altering the mechanical properties of the arterial geometry and progressively increasing the inlet pulse pressure (PP). The transmission of PP throughout the tree was shown to increase in advanced stages of disease, creating the potential for a `vicious-cycle' of damage to vasculature. Wall shear stress (WSS) was shown to be highest in the terminal arteries of the model and increased significantly with disease. A further trend observed in WSS results was that high WSS values began to `climb' the arterial tree towards the proximal vessels as disease progressed. This suggests a link between WSS and distal remodeling in pulmonary hypertensive disease, which initiates in the small muscular arteries and arterioles and spreads into larger arteries as the disease progresses.

Animal Models of Pulmonary Hypertension: Matching Disease Mechanisms to Etiology of the Human Disease

Recently a great deal of progress has been made in our understanding of pulmonary hypertension (PH). Research from the past 30 years has resulted in newer treatments that provide symptomatic improvements and delayed disease progression. Unfortunately, the cure for patients with this lethal syndrome remains stubbornly elusive. With the relative explosion of scientific literature regarding PH, confusion has arisen regarding animal models of the disease and their correlation to the human condition. This short review uniquely focuses on the clear and present need to better correlate mechanistic insights from existing and emerging animal models of PH to specific etiologies and histopathologies of human PH. A better understanding of the pathologic processes in various animal models and how they relate to the human disease should accelerate the development of newer and more efficacious therapies.

Comparison of gene expression profiles and related pathways in chronic thromboembolic pulmonary hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is one of the main causes of severe pulmonary hypertension. However, despite treatment (pulmonary endarterectomy), in approximately 15–20% of patients, pulmonary vascular resistance and pulmonary arterial pressure continue to increase. To date, little is known about the changes that occur in gene expression in CTEPH. The identification of genes associated with CTEPH may provide insight into the pathogenesis of CTEPH and may aid in diagnosis and treatment. In this study, we analyzed the gene expresion profiles of pulmonary artery endothelial cells from 5 patients with CTEPH and 5 healthy controls using oligonucleotide microarrays. Bioinformatics analyses using the Gene Ontology (GO) and KEGG databases were carried out to identify the genes and pathways specifically associated with CTEPH. Signal transduction networks were established to identify the core genes regulating the progression of CTEPH. A number of genes were found to be differentially expressed in the pulmonary artery endothelial cells from patients with CTEPH. In total, 412 GO terms and 113 pathways were found to be associated with our list of genes. All differential gene interactions in the Signal-Net network were analyzed. JAK3, GNA15, MAPK13, ARRB2 and F2R were the most significantly altered. Bioinformatics analysis may help gather and analyze large amounts of data in microarrays by means of rigorous experimental planning, scientific statistical analysis and the collection of complete data. In this study, a novel differential gene expression pattern was constructed. However, further studies are required to identify novel targets for the diagnosis and treatment of CTEPH.

MicroRNA expression profile of pulmonary artery smooth muscle cells and the effect of let-7d in chronic thromboembolic pulmonary hypertension

Abstract Chronic thromboembolic pulmonary hypertension (CTEPH) is a life-threatening condition characterized by single or recurrent pulmonary thromboemboli, which promote pulmonary vascular remodeling. MicroRNA (miRNA), is a small, noncoding RNA that is involved in multiple cell processes and functions and may participate in the pathogenesis of CTEPH. Our aims were to identify the miRNA expression signature in pulmonary artery smooth muscle cells (PASMCs) of CTEPH patients and to study the role of let-7d in CTEPH pathogenesis. The miRNA expression profile was analyzed by microarray in PASMCs of CTEPH and control patients. Differentially expressed miRNAs were selectively validated by stem-loop quantitative real-time reverse-transcription polymerase chain reaction (qRT-PCR). The role of let-7d was identified by in silico analysis, and its effect on the proliferation of PASMCs was measured by methyl thiazolyl tetrazolium (MTT). Student's unpaired t test, the Fisher exact test, and the χ(2) test were used for statistical analysis. Eighteen miRNAs were differentially expressed in PASMCs from CTEPH patients, including 12 upregulated miRNAs and 6 downregulated miRNAs; among the latter, let-7d decreased 0.58-fold in CTEPH patients, as validated by qRT-PCR. It was found that let-7d could inhibit the proliferation of PASMCs through upregulation of p21. In conclusion, PASMCs in CTEPH patients have an aberrant miRNA profile and reduced let-7d, which could promote PASMC proliferation and may be involved in the pathogenesis of CTEPH.

Pulmonary vascular diseases

Diseases of the pulmonary vasculature are a cause of increased pulmonary vascular resistance (PVR) in pulmonary embolism, chronic thromboembolic pulmonary hypertension (CTEPH), and pulmonary arterial hypertension or decreased PVR in pulmonary arteriovenous malformations on hereditary hemorrhagic telangiectasia, portal hypertension, or cavopulmonary anastomosis. All these conditions are associated with a decrease in both arterial PO2 and PCO2. Gas exchange in pulmonary vascular diseases with increased PVR is characterized by a shift of ventilation and perfusion to high ventilation-perfusion ratios, a mild to moderate increase in perfusion to low ventilation-perfusion ratios, and an increased physiologic dead space. Hypoxemia in these patients is essentially explained by altered ventilation-perfusion matching amplified by a decreased mixed venous PO2 caused by a low cardiac output. Hypocapnia is accounted for by hyperventilation, which is essentially related to an increased chemosensitivity. A cardiac shunt on a patent foramen ovale may be a cause of severe hypoxemia in a proportion of patients with pulmonary hypertension and an increase in right atrial pressure. Gas exchange in pulmonary arteriovenous malformations is characterized by variable degree of pulmonary shunting and/or diffusion-perfusion imbalance. Hypocapnia is caused by an increased ventilation in relation to an increased pulmonary blood flow with direct peripheral chemoreceptor stimulation by shunted mixed venous blood flow.

Influence of distal resistance and proximal stiffness on hemodynamics and RV afterload in progression and treatments of pulmonary hypertension: a computational study with validation using animal models

We develop a simple computational model based on measurements from a hypoxic neonatal calf model of pulmonary hypertension (PH) to investigate the interplay between vascular and ventricular measures in the setting of progressive PH. Model parameters were obtained directly from in vivo and ex vivo measurements of neonatal calves. Seventeen sets of model-predicted impedance and mean pulmonary arterial pressure (mPAP) show good agreement with the animal measurements, thereby validating the model. Next, we considered a predictive model in which three parameters, PVR, elastic modulus (EM), and arterial thickness, were varied singly from one simulation to the next to study their individual roles in PH progression. Finally, we used the model to predict the individual impacts of clinical (vasodilatory) and theoretical (compliance increasing) PH treatments on improving pulmonary hemodynamics. Our model (1) displayed excellent patient-specific agreement with measured global pulmonary parameters; (2) quantified relationships between PVR and mean pressure and PVS and pulse pressure, as well as studiying the right ventricular (RV) afterload, which could be measured as a hydraulic load calculated from spectral analysis of pulmonary artery pressure and flow waves; (3) qualitatively confirmed the derangement of vascular wall shear stress in progressive PH; and (4) established that decreasing proximal vascular stiffness through a theoretical treatment of reversing proximal vascular remodeling could decrease RV afterload.

Management of peripheral pulmonary emboli with the use of transvenous catheter-directed thrombolysis and right ventricular assist device

OBJECTIVES

Pulmonary emboli (PE) can result in significant hemodynamic instability that requires urgent intervention; however, the management of peripheral emboli has been controversial.

PATIENTS AND METHODS

We present two patients in whom a right ventricular assist device (RVAD) was used in treating peripheral pulmonary embolism, applying the technique of pulmonary artery catheter-directed thrombolysis after resuscitation with an RVAD.

RESULTS

The clot burden was not suitable for surgical embolectomy due to its peripheral locations. The patients' hemodynamic conditions improved with thrombolytic therapy and gradually were weaned off the RVAD. Follow-up scans showed near resolution of all PE.

CONCLUSION

Catheter-directed thrombolysis with an RVAD as an adjunct should be considered in management of peripheral PE.

Everolimus in patients with severe pulmonary hypertension: a safety and efficacy pilot trial

Abstract Despite the availability of vasodilating compounds, pulmonary hypertension (PH) of various origins remains a disease with a poor prognosis. In recent years, pulmonary arterial hypertension (PAH) has been recognized as a predominantly proliferative process. Everolimus, an inhibitor of the mammalian target of rapamycin (mTOR), inhibits cellular protein synthesis and growth not only in lymphocytes but also in cells of the vascular wall. Ten patients suffering from PAH ([Formula: see text]) or chronic thromboembolic PH ([Formula: see text]) with progressive disease despite therapy with at least 2 vasodilating drugs were included in a prospective open-label pilot study. All patients were treated with everolimus in addition to their prior medication. Safety and tolerability were observed throughout the study. Pulmonary vascular resistance (PVR) and 6-minute walk distance (6MWD) were considered coprimary end points. In 2 patients, study medication was stopped prematurely because of an adverse event. One patient had acute bronchitis, and the other had right heart decompensation. The remaining 8 patients exhibited a significant 31% decrease in PVR (median [interquartile range], 1,012 [688-1,344] vs. 663 [546-860] dyn s cm(-5); [Formula: see text]) and an increase in 6MWD (median [interquartile range], 236 [139-350] vs. 298 [207-450] m; [Formula: see text]) after 6 months of treatment with everolimus. In conclusion, in this pilot study antiproliferative therapy with everolimus was well tolerated in patients with PH. The observed improvements in PVR and 6MWD may stimulate further consideration of mTOR inhibition with everolimus for the treatment of PH.

Recent progress in the diagnosis and management of chronic thromboembolic pulmonary hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is a form of pulmonary hypertension caused by non-resolving thromboembolisms of the pulmonary arteries. In Japan, in contrast to Western countries, CTEPH is more prevalent in women. A Japanese multicenter study reported that a form of CTEPH unrelated to deep vein thrombosis is associated with HLA-B⁎5201, suggesting that this form of CTEPH may be associated with vasculopathy. CTEPH can be cured by pulmonary endarterectomy, provided that the thrombi are surgically accessible; thus, early diagnosis is important, and all patients with exertional dyspnea should be evaluated for pulmonary hypertension. Ventilation/perfusion scans provide an excellent non-invasive means to distinguish CTEPH from pulmonary arterial hypertension. Similarly, computed tomographic pulmonary angiograms allow for the detection of thrombi and evaluation of pulmonary hemodynamics in a minimally invasive manner. Importantly, the absence of subpleural perfusion on pulmonary angiograms can suggest the presence of small vessel disease. Small vessel disease might be involved in the pathogenesis of CTEPH, and its detection is essential in preventing operative death. Although no modern therapies for pulmonary arterial hypertension have been approved for treatment of CTEPH, a recent randomized control trial of riociguat in patients with CTEPH demonstrated that riociguat significantly improved 6-min walking distance. Further investigations into treatments that target endothelial dysfunction and hyperproliferative CTEPH cells are needed. Recently, balloon pulmonary angioplasty has emerged as a promising treatment modality in Japan. A specialized medical team, including at least one expert surgeon, should make decisions regarding patients' candidacy for pulmonary endarterectomy and/or balloon pulmonary angioplasty.

Fibrinogen Aα Thr312Ala polymorphism specifically contributes to chronic thromboembolic pulmonary hypertension by increasing fibrin resistance

Background

Polymorphisms are associated with chronic thromboembolic pulmonary hypertension (CTEPH) and pulmonary thromboembolism (PTE), but no polymorphism specific to CTEPH but not PTE has yet been reported. Fibrin resistance is associated with CTEPH, but the mechanism has not been elucidated.

Methods

Polymorphisms were analyzed in 101 CTEPH subjects, 102 PTE subjects and 108 healthy controls by Massarray or restriction fragment length polymorphism (RFLP). Plasmin-mediated cleavage of fibrin was characterized in 69 subjects (29 with CTEPH, 21 with PTE and 19 controls).

Results

Genotype frequencies and allele frequencies of fibrinogen Aα Thr312Ala were significantly higher in CTEPH subjects than in controls and PTE subjects, while there was no difference between PTE subjects and controls. The odd ratio (OR 2.037) and 95% confidence interval (95% CI, 1.262–3.289) showed that Thr312Ala polymorphism was a risk factor for CTEPH but not PTE. Fibrin from CTEPH subjects was more resistant to lysis than that from PTE subjects and controls. Fibrin resistance was significantly different between Aα Thr312Ala (A/G) genotypes within CTEPH subjects, and the fibrin with GG genotype was more resistant than that with AA and AG genotype.

Conclusions

Fibrinogen Aα Thr312Ala (A/G) polymorphism was associated with CTEPH, but not PTE, suggesting that the fibrinogen Aα Thr312Ala polymorphism may act as a potential biomarker in identifying CTEPH from PTE. GG genotype polymorphism contributes to CTEPH through increasing fibrin resistance, implying that PTE subjects with fibrinogen Aα GG genotype may need long-term anticoagulation therapy.

Balloon pulmonary angioplasty in patients with inoperable chronic thromboembolic pulmonary hypertension

OBJECTIVE

To examine the effect of balloon pulmonary angioplasty (BPA) on chronic thromboembolic pulmonary hypertension (CTEPH) in patients with inoperable disease or persistent pulmonary hypertension after pulmonary endarterectomy.

DESIGN

Observational cohort study.

SETTING

Referred patients with inoperable or persistent CTEPH.

PATIENTS

Twenty consecutive CTEPH patients (10 females), aged 60±10 years.

INTERVENTIONS BPA MAIN OUTCOME MEASURES

Right heart catheterisation, functional capacity (cardiopulmonary exercise testing (CPET) and NYHA class) and blood sampled biomarkers N-terminal pro-brain natriuretic peptide (NT-proBNP) and troponin T examined at the time of diagnosis and repeated in all patients 3 months after the last BPA.

RESULTS

Seventy-three catheterisations were performed with 18.6±6.1 BPAs per patient on segmental and subsegmental arteries. Two deaths occurred following the first BPA, with an overall 10% periprocedural death rate. Reperfusion oedema complicated seven procedures. Comparisons before and after BPA showed significant haemodynamic improvements, including decreased mean pulmonary artery pressure (mPAP) (45±11 mm Hg vs 33±10 mm Hg; p<0.001) and increased cardiac output (4.9±1.6 L/min vs 5.4±1.9 L/min; p=0.011). Reduced right ventricular strain was indicated by significantly lower plasma levels of NT-proBNP and troponin T. Significant improvement in functional capacity was evident as assessed by NYHA class (3.0±0.5 vs 2.0±0.5; p<0.001) and CPET (13.6±5.6 mL/kg/min vs 17.0±6.5 mL/kg/min; p<0.001). Seventeen patients (85%) were alive after 51±30 months of follow-up.

CONCLUSIONS

BPA may offer an alternative form of treatment in selected CTEPH patients. While prognostic markers such as haemodynamics, functional capacity and biomarkers improve, significant periprocedural complications must be recognised. Randomised trials are warranted.

Pulmonary edema predictive scoring index (PEPSI), a new index to predict risk of reperfusion pulmonary edema and improvement of hemodynamics in percutaneous transluminal pulmonary angioplasty

OBJECTIVES

This study sought to identify useful predictors for hemodynamic improvement and risk of reperfusion pulmonary edema (RPE), a major complication of this procedure.

BACKGROUND

Percutaneous transluminal pulmonary angioplasty (PTPA) has been reported to be effective for the treatment of chronic thromboembolic pulmonary hypertension (CTEPH). PTPA has not been widespread because RPE has not been well predicted.

METHODS

We included 140 consecutive procedures in 54 patients with CTEPH. The flow appearance of the target vessels was graded into 4 groups (Pulmonary Flow Grade), and we proposed PEPSI (Pulmonary Edema Predictive Scoring Index) = (sum total change of Pulmonary Flow Grade scores) × (baseline pulmonary vascular resistance). Correlations between occurrence of RPE and 11 variables, including hemodynamic parameters, number of target vessels, and PEPSI, were analyzed.

RESULTS

Hemodynamic parameters significantly improved after median observation period of 6.4 months, and the sum total changes in Pulmonary Flow Grade scores were significantly correlated with the improvement in hemodynamics. Multivariate analysis revealed that PEPSI was the strongest factor correlated with the occurrence of RPE (p < 0.0001). Receiver-operating characteristic curve analysis demonstrated PEPSI to be a useful marker of the risk of RPE (cutoff value 35.4, negative predictive value 92.3%).

CONCLUSIONS

Pulmonary Flow Grade score is useful in determining therapeutic efficacy, and PEPSI is highly supportive to reduce the risk of RPE after PTPA. Using these 2 indexes, PTPA could become a safe and common therapeutic strategy for CTEPH.

Improved survival in patients with inoperable chronic thromboembolic pulmonary hypertension

Patients with inoperable chronic thromboembolic pulmonary hypertension (Inop-CTEPH) treated with conventional therapy have a poor survival. We compare the 3-year survival between those treated with conventional therapy and those treated with conventional therapy and a combination of novel drugs. We also evaluate the clinical course. A total of 34 Inop-CTEPH consecutive patients were evaluated from 1991 to 2009 including right heart catheterization (RHC) and perfusion lung scan (PLS): 7 underwent surgical treatment while 27 were confirmed inoperable. Of these 27 patients, 12 evaluated from 1991 to 2003 (Group 1) were treated with conventional therapy and 15 evaluated from 2004 to 2009 (Group 2) were treated with conventional and novel therapies. At baseline, no group difference emerged at RHC. Based on clinical course, novel drugs and oxygen supplementation were given to patients of Group 2. Seven of these who had worse clinical course repeated RHC and four of them also PLS during therapy. Those without repeat RHC had baseline pulmonary artery mean pressure and brain natriuretic peptide (NT-proBNP) lower and mixed venous saturation (SvO2) and exercise test higher (p = 0.022, 0.015, 0.044 and 0.003, respectively). During therapy, those with repeat RHC had total pulmonary vascular resistance reduced (p = 0.012), base excess increased (p = 0.002) and significant redistribution of pulmonary blood flow at PLS. At the 3-year follow-up, survival was 86% in Group 2 and 31% in Group 1 (p = 0.031). In Inop-CTEPH patients, the clinical course may help to select drugs and the level of oxygen supply that can improve hemodynamics, gas exchange and long-term survival.

Pulmonary endarterectomy for chronic thrombo-embolic pulmonary hypertension: an institutional experience

OBJECTIVE

Pulmonary endarterectomy (PEA) is the treatment of choice for patients with chronic thrombo-embolic pulmonary hypertension (CTEPH). The aim of this study was to review our initial experience since the implementation of our program.

METHODS

Data were collected prospectively on all patients who underwent PEA between March 2011 and March 2012.

RESULTS

Forty-nine patients (20 male, 29 female, mean age 47.7 years) underwent surgery. The preoperative New York Heart Association class distribution showed the majority to be in class III or IV (n = 40). Mortality rate was 14.2% (n = 7) and the morbidity rate was 26.5% (n = 13). After PEA, the durations of mechanical ventilation, intensive care stay and hospital stay before discharge were 49.7 ± 46.1 h, 6.5 ± 5.0 days and 12.9 ± 7.5 days, respectively. The systolic and mean pulmonary artery pressure (PAP) fell significantly from 87.0 ± 26.6 mmHg and 53.8 ± 14.5 before, to 41.5 ± 12.4 mmHg and 28.5 ± 10.5 after surgery (P < 0.001 and P < 0.001, respectively). Pulmonary vascular resistance (PVR) also improved significantly from 808 ± 352.0 to 308 ± 91 dyn•s•cm(-5) (P < 0.001). Univariate analysis showed that preoperative systolic PAP, tricuspid annular plane systolic excursion, right atrial volume, right atrial pressure, forced expiratory volume in 1 s, forced vital capacity, preoperative PVR, postoperative PVR, the duration of circulatory arrest and postoperative use of extracorporeal membrane oxygenation were risk factors for mortality (P < 0.05). According to multivariate analyses, only prolonged mechanical ventilation was selected as predictive risk factor for morbidity (P = 0.005). After a median follow-up of 6.1 months, two patients died due to cerebrovascular disease and one patient needed targeted pulmonary hypertension therapy. The rest of the 39 patients showed marked improvements in their clinical status.

CONCLUSIONS

Starting a pulmonary endarterectomy program with acceptable mortality and morbidity rates and satisfactory early-term outcomes increases awareness of the CTEPH and surgery. Preoperative factors can primarily predict postoperative outcome after PEA. Identifying the risk factors in order to achieve a good result is important for the success of a PEA program. Therefore all patients diagnosed with CTEPH should be referred for consideration of PEA in a specialized centre.

Properly diagnosing pulmonary arterial hypertension

Pulmonary hypertension (PH) is found in many clinical conditions and is associated with increased morbidity and mortality. Pulmonary arterial hypertension (PAH) is a clinical condition characterized by precapillary PH without causes such as lung disease, chronic thromboembolic PH, or other rare conditions. Evaluating a patient with suspected PH requires a series of investigations intended to confirm the diagnosis, determine the clinical PH group (and, in the case of PAH group 1, the specific etiology), and evaluate the functional and hemodynamic impairment. The workup should identify the risk factors for PH (e.g., left heart disease, lung diseases associated with alveolar hypoxia, and chronic thromboembolism) versus the conditions associated with PAH group 1 (e.g., scleroderma, human immunodeficiency virus, anorexigen use, liver disease). A detailed algorithm is presented to help physicians determine the appropriate PH category. Because the presence of one condition associated with PH does not exclude another etiologies, clinicians are strongly encouraged to follow the entire algorithm. Discussions and case studies are presented describing the differentiation of PAH group 1 from PH group 2 and PAH group 1 from PH group 3; diagnosing PH group 4; determining the long-term calcium channel blocker response in those with idiopathic PAH; and determining the severity of PH.

Proximal pulmonary arterial obstruction decreases the time constant of the pulmonary circulation and increases right ventricular afterload

The time constant of the pulmonary circulation, or product of pulmonary vascular resistance (PVR) and compliance (Ca), called the RC-time, has been reported to remain constant over a wide range of pressures, etiologies of pulmonary hypertension, and treatments. We wondered if increased wave reflection on proximal pulmonary vascular obstruction, like in operable chronic thromboembolic pulmonary hypertension, might also decrease the RC-time and thereby increase pulse pressure and right ventricular afterload. Pulmonary hypertension of variable severity was induced either by proximal obstruction (pulmonary arterial ensnarement) or distal obstruction (microembolism) eight anesthetized dogs. Pulmonary arterial pressures (Ppa) were measured with high-fidelity micromanometer-tipped catheters, and pulmonary flow with transonic technology. Pulmonary ensnarement increased mean Ppa, PVR, and characteristic impedance, decreased Ca and the RC-time (from 0.46 ± 0.07 to 0.30 ± 0.03 s), and increased the oscillatory component of hydraulic load (Wosc/Wtot) from 25 ± 2 to 29 ± 2%. Pulmonary microembolism increased mean Ppa and PVR, with no significant change in Ca and characteristic impedance, increased RC-time from 0.53 ± 0.09 to 0.74 ± 0.05 s, and decreased Wosc/Wtot from 26 ± 2 to 13 ± 2%. Pulse pressure increased more after pulmonary ensnarement than after microembolism. Concomitant measurements with fluid-filled catheters showed the same functional differences between the two types of pulmonary hypertension, with, however, an underestimation of Wosc. We conclude that pulmonary hypertension caused by proximal vs. distal obstruction is associated with a decreased RC-time and increased pulsatile component of right ventricular hydraulic load.