Diagnosis and management of pulmonary arterial hypertension

Neurological involvement in hematopoietic stem cell transplantation-associated thrombotic microangiopathy

Transplantation-associated thrombotic microangiopathy (TA-TMA) is a well-recognized serious complication of hematopoietic stem cell transplantation (HSCT). The understanding of TA-TMA pathophysiology has expanded in recent years. Dysregulation of the complement system is thought to cause endothelial injury and, consequently, microvascular thrombosis and tissue damage. TA-TMA can affect multiple organs, and each organ exhibits specific features of injury. Central nervous system (CNS) manifestations of TA-TMA include posterior reversible encephalopathy syndrome, seizures, and encephalopathy. The development of neurological dysfunction is associated with a significantly lower overall survival in patients with TA-TMA. However, there are currently no established histopathological or radiological criteria for the diagnosis of CNS TMA. Patients who receive total body irradiation (TBI), calcineurin inhibitors (CNI), and severe acute and chronic graft-versus-host disease (GVHD) are at a high risk of experiencing neurological complications related to TA-TMA and should be considered for directed TA-TMA therapy. However, the incidence and clinical manifestations of TA-TMA neurotoxicity remain unclear. Studies specifically examining the involvement of CNS in TMA syndromes are limited. In this review, we discuss clinical manifestations and imaging abnormalities in patients with nervous system involvement in TA-TMA. We summarize the mechanisms underlying TA-TMA and its neurological complications, including endothelial injury, evidence of complement activation, and treatment options for TA-TMA.

Fat Grafting for the Treatment of Scleroderma

BACKGROUND

Scleroderma is a chronic connective tissue disease that results in fibrosis of the skin and internal organs. Although internal organ involvement corresponds with poor prognosis, systemic agents are effective at improving the effects of scleroderma on internal organs. In contrast, skin manifestations are universally present in all patients diagnosed with scleroderma, yet no systemic agents have been shown to be successful. Fat grafting has been shown to improve skin quality and improve contour irregularities and may be helpful in the treatment of patients with scleroderma.

METHODS

The authors performed a thorough review of the pathophysiology of scleroderma and the current treatment options for scleroderma. The efficacy of fat grafting for the treatment of scleroderma and the mechanism by which fat grafting improves outcomes was also discussed.

RESULTS

Scleroderma is characterized by chronic inflammation and vascular compromise that leads to fibrosis of the skin and internal organs. Fat grafting has recently been the focus of significant basic science research. It has been shown to reduce inflammation, reduce fibrosis by limiting extracellular matrix proteins and increasing collagenase activity, and provide structural support through stem cell proliferation and differentiation. The adipocytes, adipose stem cells, endothelial cells, and vascular smooth muscle cells in the processed fat likely contribute to the effectiveness of this treatment.

CONCLUSIONS

Fat grafting in scleroderma patients likely improves skin manifestations by recreating fullness, correcting contour deformities, and improving skin quality. The injected fat provides a mixture of cells that influences the recipient site, resulting in improved outcomes.

Chronic thromboembolic pulmonary hypertension as the first manifestation of nephrotic syndrome in a 12-year-old child

RATIONALE

Chronic thromboembolic pulmonary hypertension (CTEPH) is rare in children and determining the underlying etiologies is essential for treatment. Venous thromboembolism, a well-known complication in nephrotic syndrome (NS), always occurrs during the treatment in course of the disease. However, CTEPH as the first manifestation of NS has not been reported till now.

PATIENT CONCERNS

A 12-year-old boy initially complained of hemoptysis, cough and shortness of breath with exertion, any symptoms regarding NS such as edema were not presented. Due to the identification of P2 enhancement, liver enlargement (2 cm below the rib) and jugular vein distension, pulmonary hypertension (PH) was firstly suspected and ultimately confirmed by detection of enlargement of right atrium (RA) and right ventricle (RV) enlargement (RA = 45mm, RV = 30mm), mild tricuspid valve regurgitation (TR) and elevation of pulmonary arterial pressure (63 mmHg) on echocardiogram. In order to search the underlying causes of PH, series of targeted laboratory evaluation and imaging were conducted, and pulmonary arterial embolism (PE) in inferior lobes of double lungs was found on chest contrast-enhanced computed tomography.

DIAGNOSIS

NS was unexpectedly discovered by detection of lower serum albumin level (24.4 g/L), severe proteinuria (+++, 4.62 g/24 h) when we were searching for the predisposing factors causing thromboembolism.

INTERVENTIONS AND OUTCOMES

After treatment of NS, the symptom regarding shortness of breath with exertion gradually became less apparent and was relieved one month later. Proteinuria and microscopic hematuria also disappeared. Encouragingly, RA and RV dilation, and the pulmonary arterial pressure almost returned to a normal range half a year later, with alleviation of MR.

LESSONS

CTEPH can occur rarely in children and NS is an important predisposing factor. PE could be the first manifestation of NS. When pediatricians encounter children with PE or CTEPH, NS as the underlying etiology should be considered. Except for renal venous thrombosis, the possibility of PE needs to be paid more attention in children with NS.

Pulmonary Arterial Hypertension: Pathophysiology and Treatment

Pulmonary arterial hypertension (PAH), the first category of pulmonary hypertension, is a chronic and progressive disorder characterised by angioproliferative vasculopathy in the pulmonary arterioles, leading to endothelial and smooth muscle proliferation and dysfunction, inflammation and thrombosis. These changes increase pulmonary vascular resistance and subsequent pulmonary arterial pressure, causing right ventricular failure which leads to eventual death if untreated. The management of PAH has advanced rapidly in recent years due to improved understanding of the condition's pathophysiology, specifically the nitric oxide, prostacyclin-thromboxane and endothelin-1 pathways. Five classes of drugs targeting these pathways are now available: phosphodiesterase-5 inhibitors, soluble guanylate cyclase stimulators, prostacyclin analogues, prostacyclin receptor agonists and endothelin receptor antagonists. These developments have led to substantial improvements in mortality rate in recent decades. Recently, long-term studies have demonstrated sustained progression-free survival and have created a new paradigm of initial combination therapy. Despite these targeted therapies, PAH is still associated with significant morbidity and mortality. As such, further research into broadening our understanding of PAH pathophysiology is underway with potential of increasing the repertoire of drugs available.

Human factors and usability engineering in the development of SMT-101 for the treatment of pulmonary arterial hypertension

BACKGROUND

SMT-101, a novel, proprietary, water-resistant wearable infusion pump prefilled with a preset dosage of treprostinil, was designed to address many of the administration-related shortcomings of existing parenteral therapy for pulmonary arterial hypertension (PAH). The objective of the human factors (HF) program was to demonstrate that the SMT-101 system is safe and effective when used by patients with PAH, their caregivers, or healthcare providers.

METHODS

The HF program for SMT-101 consisted of 8 studies (148 participants): an ethnographic study, an online survey of patients with PAH, 4 formative studies, a study of the instructions for use (IFU), and a summative study for validation. The pump and IFU were iteratively modified using observational data and participant feedback to inform subsequent improvements throughout the HF program to optimize safe use of SMT-101 before the final study.

RESULTS

The results of the summative study demonstrated that the design of the SMT-101 wearable, pre-filled infusion pump and IFU are safe and effective for use.

CONCLUSIONS

In accordance with regulatory guidelines, the usability and HF aspects of SMT-101 were developed and refined through a rigorous HF program in patients with PAH and healthcare providers, which culminated in a summative study that validated the usability and use-safety of SMT-101.

Expression of key enzymes in the mevalonate pathway are altered in monocrotaline-induced pulmonary arterial hypertension in rats

Pulmonary arterial hypertension (PAH) is a serious pulmonary vascular disease. The changes in the structure, function and metabolism of endothelial cells are some of the important features of PAH. Previous studies have demonstrated that the mevalonate pathway is important in cardiovascular remodeling. However, whether the mevalonate pathway is involved in the development of PAH remains to be elucidated. The present study aimed to investigate the expression pattern of mevalonate pathway-related enzymes in monocrotaline (MCT)-induced PAH. F344 rats were randomly divided into two groups (n=6/group): Control group rats were injected with a single dose of saline, and MCT group rats were injected with a single dose of MCT (60 mg/kg). After 4 weeks, the right ventricular systolic pressure (RVSP) was measured, and lung and pulmonary artery tissue samples were collected. It was demonstrated that the RVSP increased and pulmonary vascular remodeling was detected in the PAH group. The expression levels of the enzymes farnesyldiphosphate synthase farnesyltransferase α and geranylgeranyltransferase type I increased in the PAH group, which suggested that the mevalonate pathway may be involved in the pathological development of PAH.

New approaches in the diagnosis, pathophysiology, and treatment of pediatric hematopoietic stem cell transplantation-associated thrombotic microangiopathy

Hematopoietic stem cell transplantation (HSCT)-associated thrombotic microangiopathy (TA-TMA) is an understudied complication of HSCT that significantly affects transplant-related morbidity and mortality. Over the past several decades, the cause of TA-TMA has remained unknown, limiting treatment options to non-specific therapies adapted from other diseases. Recent prospective studies dedicated to the study of TA-TMA have provided new insights into the pathogenesis of, and genetic susceptibility to TA-TMA, raising awareness of this important transplant complication and allowing for the identification of potentially novel therapeutic targets. Specifically, many patients with TA-TMA develop multi-organ tissue injury through endothelial damage mediated by the activation of the complement pathway, leading to rational therapeutic strategies including complement blockade. This new knowledge has the potential to favorably influence clinical practice and change the standard of care for how patients with TA-TMA are managed. In this review, we summarize novel approaches to the recognition and management of TA-TMA, using case examples to illustrate key clinical points that hopefully lead to improved short and long-term outcomes for these complex HSCT patients, who remain at significant risk for treatment-related morbidity and mortality.

Pulmonary arterial hypertension in a child with stage-IV neuroblastoma after autologous hematopoietic stem cell transplantation and review of the literature

PH is a rare condition with high mortality rate after pediatric HSCT. As clinical presentation is non-specific and may mimic other conditions, a high degree of suspicion is required for diagnosis. Here, we present a patient with stage-IV neuroblastoma who developed PAH after autologous HSCT. After exclusion of other causes of PH, we regarded that this condition was secondary to HSCT.

A new paradigm: Diagnosis and management of HSCT-associated thrombotic microangiopathy as multi-system endothelial injury

Hematopoietic stem cell transplantation (HSCT)-associated thrombotic microangiopathy (TA-TMA) is now a well-recognized and potentially severe complication of HSCT that carries a high risk of death. In those who survive, TA-TMA may be associated with long-term morbidity and chronic organ injury. Recently, there have been new insights into the incidence, pathophysiology, and management of TA-TMA. Specifically, TA-TMA can manifest as a multi-system disease occurring after various triggers of small vessel endothelial injury, leading to subsequent tissue damage in different organs. While the kidney is most commonly affected, TA-TMA involving organs such as the lung, bowel, heart, and brain is now known to have specific clinical presentations. We now review the most up-to-date research on TA-TMA, focusing on the pathogenesis of endothelial injury, the diagnosis of TA-TMA affecting the kidney and other organs, and new clinical approaches to the management of this complication after HSCT.

Cerium oxide nanoparticles attenuate monocrotaline induced right ventricular hypertrophy following pulmonary arterial hypertension

Cerium oxide (CeO2) nanoparticles have been posited to exhibit potent anti-oxidant activity which may allow for the use of these materials in biomedical applications. Herein, we investigate whether CeO2 nanoparticle administration can diminish right ventricular (RV) hypertrophy following four weeks of monocrotaline (MCT)-induced pulmonary arterial hypertension (PAH). Male Sprague Dawley rats were randomly divided into three groups: control, MCT only (60 mg/kg), or MCT + CeO2 nanoparticle treatment (60 mg/kg; 0.1 mg/kg). Compared to the control group, the RV weight to body weight ratio was 45% and 22% higher in the MCT and MCT + CeO2 groups, respectively (p < 0.05). Doppler echocardiography demonstrated that CeO2 nanoparticle treatment attenuated monocrotaline-induced changes in pulmonary flow and RV wall thickness. Paralleling these changes in cardiac function, CeO2 nanoparticle treatment also diminished MCT-induced increases in right ventricular (RV) cardiomyocyte cross sectional area, β-myosin heavy chain, fibronectin expression, protein nitrosylation, protein carbonylation and cardiac superoxide levels. These changes with treatment were accompanied by a decrease in the ratio of Bax/Bcl2, diminished caspase-3 activation and reduction in serum inflammatory markers. Taken together, these data suggest that CeO2 nanoparticle administration may attenuate the hypertrophic response of the heart following PAH.

Emotional symptoms and quality of life in patients with pulmonary arterial hypertension

BACKGROUND

Limited evidence exists on the nature and degree of emotional problems in pulmonary arterial hypertension (PAH) and their association with patients' health-related quality of life (HRQOL).

METHODS

This cross-sectional study examined the presence of depression, anxiety, and stress symptoms, and their association with disease-specific and generic HRQOL. A total of 101 patients (73% women) with PAH (age, 55.4 ± 16.4 years; 42.6% in New York Heart Association [NYHA] class II) completed the Depression, Anxiety, and Stress Scale, the generic Medical Outcomes Study Short-Form 36-Item (SF-36) Health Survey, and the disease-specific Minnesota Living With Heart Failure Questionnaire (MLHFQ) HRQOL instrument. The association between emotional problems and HRQOL was determined using multivariable linear regression analyses, controlling for demographic and disease-related characteristics.

RESULTS

Of the patients, 32.6%, 48%, and 27.6% experienced depressive, anxiety or stress symptoms, respectively. HRQOL was >1 standard deviation below population norms for the SF-36 Physical Component Summary. Depressive symptoms, NYHA class, and being disabled explained 46% of the total variance of the MLHFQ. Emotional problems did not contribute to the SF-36 Physical Component Summary but explained part of the variance of the physical sub-scales of the SF-36 role limitations due to physical problems, bodily pain, and general health.

CONCLUSIONS

The high presence of emotional problems warrants regular screening and appropriate psychotherapeutic and/or pharmacological treatment. Which strategies could improve PAH patients' HRQOL remains to be investigated.

Redox signaling as a therapeutic target to inhibit myofibroblast activation in degenerative fibrotic disease

Degenerative fibrotic diseases encompass numerous systemic and organ-specific disorders. Despite their associated significant morbidity and mortality, there is currently no effective antifibrotic treatment. Fibrosis is characterized by the development and persistence of myofibroblasts, whose unregulated deposition of extracellular matrix components disrupts signaling cascades and normal tissue architecture leading to organ failure and death. The profibrotic cytokine transforming growth factor beta (TGFβ) is considered the foremost inducer of fibrosis, driving myofibroblast differentiation in diverse tissues. This review summarizes recent in vitro and in vivo data demonstrating that TGF β-induced myofibroblast differentiation is driven by a prooxidant shift in redox homeostasis. Elevated NADPH oxidase 4 (NOX4)-derived hydrogen peroxide (H2O2) supported by concomitant decreases in nitric oxide (NO) signaling and reactive oxygen species scavengers are central factors in the molecular pathogenesis of fibrosis in numerous tissues and organs. Moreover, complex interplay between NOX4-derived H2O2 and NO signaling regulates myofibroblast differentiation. Restoring redox homeostasis via antioxidants or NOX4 inactivation as well as by enhancing NO signaling via activation of soluble guanylyl cyclases or inhibition of phosphodiesterases can inhibit and reverse myofibroblast differentiation. Thus, dysregulated redox signaling represents a potential therapeutic target for the treatment of wide variety of different degenerative fibrotic disorders.

The incidence and severity of pulmonary hypertension in obstructive sleep apnea with hypothyroidism

BACKGROUND

Hypothyroidism and obstructive sleep apnea (OSA) are both common health problems and can be seen together. Each of these 2 diseases can cause pulmonary hypertension (PH). We aimed to determine whether hypothyroidism with OSA has a significant effect on the frequency and severity of PH.

MATERIAL AND METHODS

A total of 236 patients were included in the study. Patients were divided into 3 groups: Group I, Obstructive Sleep Apnea (n=149); Group II, Hypothyroidism (n=56); and Group III, Obstructive Sleep Apnea-Hypothyroidism (n=31). All patients underwent polysomnography and echocardiography and serum levels of thyroid-stimulating hormone (TSH) and free thyroxine 4 (FT4) were analyzed.

RESULTS

There were 167 male and 69 female participants, and the mean age was 47.8 ± 11.5 (Group I: 81.9% male, 18.1% female; Group II: 44.6% male, 55.4% female; Group III: 64.6% male, 35.4% female). Distribution of mean pulmonary arterial pressure on echocardiography was statistically different among the 3 groups (x(2)=14.99, p=0.006). When adjusted according to the apnea-hypopnea index (AHI), age, and body mass index (BMI), a significant relation with PH was determined (p=0.002).

CONCLUSIONS

The combination of hypothyroidism with OSA is associated with an increased frequency and severity of PH. When PH is found out of line with the severity of OSA, thyroid dysfunction should be investigated.

Provider recognition and response to echocardiographic findings indicating pulmonary hypertension in the Veterans affairs medical center population

PH occurs alone or in association with many disorders. Many patients with transthoracic echocardiography (TTE) findings suggesting PH never receive additional evaluation. Patient characteristics and echocardiographic data associated with increased recognition of PH have not been fully evaluated. We evaluated TTE reports at the Cincinnati Veterans Affairs Medical Center from 2005 to 2006 retrospectively for findings highly indicative of PH: Estimated systolic pulmonary artery pressure (sPAP) ≥40 mmHg, increased right atrial or right ventricular (RV) size, or reduced RV function. Only patients with left ventricular ejection fraction (LVEF) ≥50% and no known diagnosis of PH were included. Patient characteristics, TTE findings, provider recognition rates, and subsequent referral for additional evaluation were assessed. A total of 227 of 3,960 (5.7%) TTE reports revealed findings indicating possible PH. Providers acknowledged possible PH in 53 (23.4%) reports. Recognized PH was predicted by increased RV size (odds ratio (OR) = 5.07, P < 0.001), increased right atrial dimension (OR = 6.45, P < 0.001), decreased RV function (OR = 8.86, P < 0.001), and increased PAP (OR = 1.04 corresponding to each unit increase of PAP, P < 0.01). Patients with comorbid obstructive sleep apnea (OSA), interstitial lung disease, and dyspnea were also more likely to be recognized (OR = 3.63, P = 0.021; OR = 10.98, P = 0.004; OR = 2.39, P = 0.007, respectively). The 12-month mortality rate for recognized patients, 11.3% (7/53), was lower than for unrecognized patients, 25.3% (44/174; P = 0.03). Providers recognized less than one in four patients with echocardiographic evidence suggesting PH. Echocardiography reports revealing higher PAP and right heart dilation and dysfunction are associated with increased acknowledgement of possible PH.

Pulmonary hypertension after hematopoietic stem cell transplantation

Pulmonary hypertension (PH) is a potentially fatal complication of hematopoietic stem cell transplantation (HSCT). Given its nonspecific clinical presentation, it is likely that this clinical entity is underdiagnosed after HSCT. Data describing the incidence, risk factors, and etiology of PH in HSCT recipients are minimal. Physicians caring for HSCT recipients should be aware of this severe post-transplant complication because timely diagnosis and treatment may allow improved clinical outcomes. We summarize the pathophysiology, clinical presentation, diagnosis, and management of PH in HSCT recipients.

Effect of bosentan on exercise capacity and clinical worsening in patients with dual down and eisenmenger syndrome

This single-center, retrospective analysis evaluated long-term bosentan treatment in adult patients (n = 7) with both Down and Eisenmenger syndromes (DS-ES). Laboratory tests, 6-minute walk distance (6MWD), functional class, and Doppler echocardiography were assessed at baseline and during 2 years' follow-up. Improvements or maintenance of 6MWD were observed (68 m improvement from baseline at month 12) after bosentan initiation. 6MWD was maintained up to year 2. Overall, 6 patients experienced a significant improvement in functional class during 2 years' therapy (P = 0.01). There were no significant changes in parameters measured by Doppler echocardiography. None of the patients required either hospitalization or additional pulmonary arterial hypertension (PAH) therapy because of PAH progression. Bosentan treatment was generally well tolerated; no liver function abnormalities or serious adverse drug reactions were noted. In this DS-ES cohort, bosentan seemed to be well tolerated and clinically effective.

Factors associated with adherence to phosphodiesterase type 5 inhibitors for the treatment of pulmonary arterial hypertension

OBJECTIVES

To assess factors associated with adherence to phosphodiesterase type 5 inhibitors (PDE5Is) in the management of pulmonary arterial hypertension (PAH).

METHODS

This study analyzed pharmacy benefit claims of naïve Adcirca and Revatio users between January 1, 2008 and December 31, 2010. Patients were considered adherent if their proportion of days covered (PDC) was ≥ 80% over a 6-month period. Logistic regressions were estimated to assess the factors associated with adherence. Analyses were stratified by use of a specialty pharmacy or retail pharmacy. A sensitivity analysis was performed by excluding individuals with 90-day supply.

RESULTS

Of the total of 2143 patients included, 46.8% were adherent. Adherence was higher among 930 specialty pharmacy users (65.6%) than 1213 retail pharmacy users (32.3%, p < 0.001). Adherence was higher among Adcirca users (60.7%; approved dose 40 mg once-daily) than Revatio users (44.3%, p < 0.001; approved dose 20 mg thrice-daily). Among retail pharmacy users, adherence was higher in patients using Adcirca (OR = 2.59; 95% CI = 1.60-4.22) and patients with an index prescription given by pulmonologists (OR = 1.70; 95% CI = 1.15-2.50), while lower in patients with higher copayment ($51-$250: OR = 0.61, 95% CI = 0.42-0.90; $251+: OR = 0.57, 95% CI = 0.39-0.83). Among specialty pharmacy users, only high copayment ($251+: OR = 0.56, 95% CI = 0.35-0.90) was found to be a significant factor for non-adherence. After excluding individuals with 90-day supply, adherence rate was 29.6% in retail pharmacy and 57.9% in specialty pharmacy (p < 0.001), and regression results were similar.

LIMITATIONS

Diagnosis of PAH was not confirmed without access to medical claims. Pharmacy refill records might not reflect actual consumption. Adherence evaluated for 6 months might not be generalizable to longer periods.

CONCLUSION

Adherence to PDE5Is for PAH is sub-optimal. The findings suggest that adherence to PDE5Is in patients with PAH is associated with the use of specialty pharmacy, simpler dosing frequency, a lower financial barrier, and a prescription given by pulmonologists.

Therapeutic targeting of redox signaling in myofibroblast differentiation and age-related fibrotic disease

Myofibroblast activation plays a central role during normal wound healing. Whereas insufficient myofibroblast activation impairs wound healing, excessive myofibroblast activation promotes fibrosis in diverse tissues (including benign prostatic hyperplasia, BPH) leading to organ dysfunction and also promotes a stromal response that supports tumor progression. The incidence of impaired wound healing, tissue fibrosis, BPH, and certain cancers strongly increases with age. This paper summarizes findings from in vitro fibroblast-to-myofibroblast differentiation systems that serve as cellular models to study fibrogenesis of diverse tissues. Supported by substantial in vivo data, a large body of evidence indicates that myofibroblast differentiation induced by the profibrotic cytokine transforming growth factor beta is driven by a prooxidant shift in redox homeostasis due to elevated production of NADPH oxidase 4 (NOX4)-derived hydrogen peroxide and supported by concomitant decreases in nitric oxide/cGMP signaling and reactive oxygen species (ROS) scavenging enzymes. Fibroblast-to-myofibroblast differentiation can be inhibited and reversed by restoring redox homeostasis using antioxidants or NOX4 inactivation as well as enhancing nitric oxide/cGMP signaling via activation of soluble guanylyl cyclases or inhibition of phosphodiesterases. Current evidence indicates the therapeutic potential of targeting the prooxidant shift in redox homeostasis for the treatment of age-related diseases associated with myofibroblast dysregulation.

Pulmonary hypertension in parenchymal lung disease

Idiopathic pulmonary arterial hypertension (IPAH) has been extensively investigated, although it represents a less common form of the pulmonary hypertension (PH) family, as shown by international registries. Interestingly, in types of PH that are encountered in parenchymal lung diseases such as interstitial lung diseases (ILDs), chronic obstructive pulmonary disease (COPD), and many other diffuse parenchymal lung diseases, some of which are very common, the available data is limited. In this paper, we try to browse in the latest available data regarding the occurrence, pathogenesis, and treatment of PH in chronic parenchymal lung diseases.

Pulmonary arterial hypertension in pediatric patients with hematopoietic stem cell transplant-associated thrombotic microangiopathy

Pulmonary arterial hypertension (PAH) is rarely included in the differential diagnosis of cardiorespiratory failure after pediatric hematopoietic stem cell transplant (HSCT) as the clinical presentation is nonspecific and may mimic other etiologies. The pathogenesis of PAH in HSCT is poorly understood and the diagnosis requires a high degree of suspicion. We describe 5 children diagnosed with PAH after allogeneic HSCT. All 5 patients had prolonged clinical signs of transplantation-associated thrombotic microangiopathy (TA-TMA) when they presented with hypoxemic respiratory failure and evidence of PAH. Four of the 5 patients had echocardiographic evidence of PAH, and 1 patient was diagnosed with PAH only on autopsy. PAH was diagnosed a median of 76 days (range, 56-101 days) after a diagnosis of TA-TMA. Despite aggressive medical management, including inhaled nitric oxide, 4 of the 5 patients died. One patient recovered from PAH after 11 months of sildenafil therapy. Three of the 4 deceased patients had an autopsy performed, demonstrating severe pulmonary vascular disease consistent with TA-TMA and severe PAH. We conclude that TA-TMA can be associated with significant pulmonary vascular injury presenting as hypoxemic respiratory failure with PAH after HSCT. Pediatric patients with unexplained hypoxemia after HSCT should be evaluated for both transplantation complications, TA-TMA and PAH, accordingly.

Etiopathogenetic mechanisms of pulmonary hypertension in sleep-related breathing disorders

Obstructive sleep apnea syndrome is a common disorder with significant health consequences and is on the rise in consonance with the obesity pandemic. In view of the association between sleep-disordered breathing and pulmonary hypertension as depicted by multiple studies, current clinical practice guidelines categorize obstructive sleep apnea as a risk factor for pulmonary hypertension and recommend an assessment for sleep disordered breathing in evaluating patients with pulmonary hypertension. The dysregulatory mechanisms associated with hypoxemic episodes observed in sleep related breathing disorders contribute to the onset of pulmonary hypertension and identification of these potentially treatable factors might help in the reduction of overall cardiovascular mortality.

Pulmonary veno-occlusive disease: a misnomer?

Pulmonary veno-occlusive disease (PVOD) is a rare entity with non-specific signs and symptoms and is nearly always associated with a dismal prognosis. This review will first consider pulmonary hypertension in general and then will focus on PVOD specifically with particular attention to the pathophysiology of the disease. Classically PVOD is described as a disease primarily involving obstructed venules, with the arterial side of the circulation involved to a lesser degree. This article discusses the demographics of affected individuals; the ways in which an accurate diagnosis can be made, including imaging features; predisposing diseases and associated disorders; and potential treatment.