Pulmonary arterial hypertension in the pediatric age

Idiopathic pulmonary arterial hypertension - a unrecognized cause of high-shear high-flow haemostatic defects (otherwise referred to as acquired von Willebrand syndrome) in children

Acquired von Willebrand syndrome (AVWS) is reported in high-flow high-shear congenital cardiac disorders. We hypothesized that the narrowed pulmonary vasculature in idiopathic pulmonary arterial hypertension (IPAH) may induce AVWS. We conducted a cross-sectional evaluation of children with IPAH. Patients with bleeding symptoms and/or laboratory abnormalities (thrombocytopenia, anomalies in coagulation screening tests) were tested in-depth for haemostatic defects. Fourteen children were followed with IPAH of which 8 were eligible. Four children exhibited abnormal bleeding scores (International Society on Thrombosis and Haemostasis Bleeding Assessment Tool: 3-5). All 8 patients showed very prolonged platelet function analyser (PFA)-100 closure times. Six children demonstrated either mild thrombocytopenia or low-normal von Willebrand factor (VWF) antigen (VWF:Ag) or VWF activity [mean (range), in iu/dl: VWF:Ag: 70 (61-91); VWF activity: 57 (34-70)]. Average VWF collagen binding capacity (VWF:CB) was 64 iu/dl (range: 53-123 iu/dl), with low-normal VWF activity/VWF:Ag or VWF:CB/VWF:Ag ratios occurring in five patients. All children had normal multimers distribution patterns. One patient underwent a lung transplantation, with normalization of haemostatic abnormalities post-surgery. Overall, 8 out of 14 children with IPAH had mild to moderate bleeding symptoms and/or laboratory abnormalities in keeping with AVWS. Normalization of the haemostatic defects following lung transplantation and lack of family history of bleeding attests to the acquired nature of their defects.

mTOR-Notch3 signaling mediates pulmonary hypertension in hypoxia-exposed neonatal rats independent of changes in autophagy

BACKGROUND/AIM

Mammalian target of rapamycin (mTOR) is a pivotal regulator of cell proliferation, survival, and autophagy. Autophagy is increased in adult experimental chronic pulmonary hypertension (PHT), but its contributory role to pulmonary vascular disease remains uncertain and has yet to be explored in the neonatal animal. Notch is a major pro-proliferative pathway activated by mTOR. A direct relationship between autophagy and Notch signaling has not been previously explored. Our aim was to examine changes in mTOR-, Notch-, and autophagy-related pathways and the therapeutic effects of autophagy modulators in experimental chronic neonatal PHT secondary to chronic hypoxia.

METHODS

Rat pups were exposed to normoxia or hypoxia (13% O₂ ) from postnatal days 1-21, while receiving treatment with temsirolimus (mTOR inhibitor), DAPT (Notch inhibitor), or chloroquine (inhibitor of autophagic flux).

RESULTS

Exposure to hypoxia up-regulated autophagy and Notch3 signaling markers in lung, pulmonary artery (PA), and PA-derived smooth muscle cells (SMCs). Temsirolimus prevented chronic PHT and attenuated PA and SMC signaling secondary to hypoxia. These effects were replicated by DAPT. mTOR or Notch inhibition also down-regulated smooth muscle content of platelet-derived growth factor β-receptor, a known contributor to vascular remodeling. In contrast, chloroquine had no modifying effects on markers of chronic PHT. Knockdown of Beclin-1 in SMCs had no effect on hypoxia-stimulated Notch3 signaling.

CONCLUSIONS

mTOR-Notch3 signaling plays a critical role in experimental chronic neonatal PHT. Inhibition of autophagy did not suppress Notch signaling and had no effect on markers of chronic PHT.

Simvastatin prevents and reverses chronic pulmonary hypertension in newborn rats via pleiotropic inhibition of RhoA signaling

Chronic neonatal pulmonary hypertension (PHT) frequently results in early death. Systemically administered Rho-kinase (ROCK) inhibitors prevent and reverse chronic PHT in neonatal rats, but at the cost of severe adverse effects, including systemic hypotension and growth restriction. Simvastatin has pleiotropic inhibitory effects on isoprenoid intermediates that may limit activity of RhoA, which signals upstream of ROCK. We therefore hypothesized that statin treatment would safely limit pulmonary vascular RhoA activity and prevent and reverse experimental chronic neonatal PHT via downstream inhibitory effects on pathological ROCK activity. Sprague-Dawley rats in normoxia (room air) or moderate normobaric hypoxia (13% O2) received simvastatin (2 mg·kg−1·day−1 ip) or vehicle from postnatal days 1–14 (prevention protocol) or from days 14–21 (rescue protocol). Chronic hypoxia increased RhoA and ROCK activity in lung tissue. Simvastatin reduced lung content of the isoprenoid intermediate farnesyl pyrophosphate and decreased RhoA/ROCK signaling in the hypoxia-exposed lung. Preventive or rescue treatment of chronic hypoxia-exposed animals with simvastatin decreased pulmonary vascular resistance, right ventricular hypertrophy, and pulmonary arterial remodeling. Preventive simvastatin treatment improved weight gain, did not lower systemic blood pressure, and did not cause apparent toxic effects on skeletal muscle, liver or brain. Rescue therapy with simvastatin improved exercise capacity. We conclude that simvastatin limits RhoA/ROCK activity in the chronic hypoxia-exposed lung, thus preventing or ameliorating hemodynamic and structural markers of chronic PHT and improving long-term outcome, without causing adverse effects.

Assessment of pulmonary arterial hypertension and vascular resistance by measurements of the pulmonary arterial flow velocity curve in the absence of a measurable tricuspid regurgitant velocity in childhood congenital heart disease

This study aimed to determine mean pulmonary arterial pressure (PAPmean) and pulmonary vascular resistance (PVR) using transthoracic echocardiography (TTE) measurements of the pulmonary artery flow velocity curve in children with pulmonary arterial hypertension (PAH) and congenital heart disease when the tricuspid regurgitant velocity (TRV) is not sufficient. This study enrolled 29 congenital heart disease cases with pulmonary arterial hypertension and 40 healthy subjects followed at our center. The mean age was 66.9 ± 77.9 months in the patient group and 76.3 ± 62.1 months in the control group. A positive correlation was found between TRV and systolic pulmonary arterial pressure (r = 0.394, p = 0.035, 95% confidence interval [CI] = 0.032-0.665), whereas a negative correlation was found between corrected acceleration time (AcTc) and PAPmean (r = -0.559, p = 0.002, 95% CI = -0.768 to -0.242). Furthermore, a negative correlation was found between parameters TRV and AcTc (r = -0.383, p = 0.001, 95% CI = -0.657 to -0.019). Based on the cutoff criterion of 124 ms for AcTc, sensitivity was found to be 79.3% and specificity to be 77.5% in distinguishing between the PAH patients and the healthy control patients (receiver operating characteristic [ROC] area under the curve [AUC] = 0.804, 95% CI = 0.691-0.890, p < 0.0001). The sensitivity and specificity of the concomitant use of AcTc and/or TRV were found to be 90 and 73%, respectively, in distinguishing between the PAH patients and the the healthy control patients. The data obtained by TTE also can be appropriate for measuring PAPmean, PVR, and the vasoreactivity test and for determining the priority of implementing cardiac catheterization even if there is no measurable TRV value.

Idiopathic pulmonary hypertension causing acquired von Willebrand disease and menorrhagia

BACKGROUND

Von Willebrand disease (VWD) maybe inherited or acquired; both etiologies can be associated with heavy menstrual bleeding. Pulmonary arterial hypertension may result in acquired VWD due to the destruction of high molecular weight von Willebrand multimers. We report a case of menorrhagia due to acquired VWD in a patient with idiopathic pulmonary hypertension.

CASE

An adolescent female with known idiopathic pulmonary hypertension developed acquired VWD. Her primary disease necessitates the use of platelet inhibitors and intermittent anticoagulation. At menarche she also developed menorrhagia due to acquired VWD. She is currently controlled with stimate and progesterone-only therapy. VWD in a patient with idiopathic pulmonary hypertension causing menorrhagia. Although VWD and menorrhagia are commonly linked, the treatment and disease process in a patient with idiopathic pulmonary arterial hypertension is incredibly complex.

Management of pulmonary arterial hypertension in children

In this review we discuss the new anti- Pulmonary Arterial Hypertension [PAH] drugs and the available data on their use in paediatric PAH. Treatment of patients with PAH, children and adults, is aimed at a reduction of symptoms, survival and improvement of haemodynamics as well as exercise capacity. PAH may reflect significant different disease conditions in infants and children when compared to PAH in adults. In contrast to adult PAH, characterized mainly by idiopathic PAH and PAH associated with connective tissue disease, more than half of the cases of PAH in children are associated with congenital heart disease. Therefore, efficacy of PAH drugs in these diseases can not be extrapolated from that in adults with PAH.

Pulmonary hypertension in preterm infants with bronchopulmonary dysplasia

Background and Objectives

With the increasing survival of preterm infants, pulmonary hypertension (PH) related to bronchopulmonary dysplasia (BPD) has become an important complication. The aim of this study was to investigate the characteristics and outcome of PH in preterm infants with BPD and to identify the risk factors for PH.

Subjects and Methods

We reviewed the records of 116 preterm infants with BPD cared for at a single tertiary center between 2004 and 2008.

Results

Twenty-nine (25%) infants had PH >2 months after birth. PH occurred initially at a median age of 65 days (range, 7-232 days). Severe BPD, a birth weight <800 g, long-term ventilator care and oxygen supplementation, a high ventilator setting, infection, and a patent ductus arteriosus (PDA) were related to PH based on univariate analysis (p<0.05). The infants who had longer oxygen supplementation were significantly more likely to have PH (odds ratio, 18.5; 95% confidence interval, 4.1-84.6; p<0.001). PH was improved in 76% of infants after a median of 85 days (range, 20-765 days). Four infants (14%) died. The death of 3 infants was attributed to PH.

Conclusion

BPD was frequently complicated by PH. Although PH resolved in the majority of infants, PH in preterm infants with BPD can be fatal. Regular screening for PH and adequate management are required.

Superior vena cava Doppler flow changes in rabbits with acute thromboembolic pulmonary hypertension

OBJECTIVE

The purpose of this study was to explore the superior vena cava (SVC) Doppler flow changes in rabbits with acute thromboembolic pulmonary hypertension (ATEPAH) and its value in evaluating pulmonary pressure.

METHODS

The systolic peak flow velocity (SPV), ventricular reverse peak flow velocity (VrPV), diastolic peak flow velocity (DPV), and atrial reverse peak flow velocity (ArPV) of the SVC were measured on end expiration with pulsed wave Doppler echocardiography in 30 rabbits with different degrees of ATEPAH. Linear regression and the Bland-Altman method were used to analyze the correlation of Doppler flow velocities of the SVC to the catheter-measured pulmonary arterial systolic pressure (PASP).

RESULTS

The SPV values of all groups were significantly lower after pulmonary embolism (PE) than before PE (P < .05). The VrPV values of the mild and the moderate groups but not the severe group were significantly higher after PE than before PE. The DPV values of the severe ATEPAH group were significantly lower after PE than before PE, but they were not lower in the other 2 groups. The SPV had a significantly negative relationship with the PASP (r = -0.692; P < .0001). The VrPV/SPV ratios of all groups showed a significant positive correlation with the PASP (r = 0.698; P < .0001). The end-diastolic diameter of the SVC gradually enlarged with the rapidly increased PASP and showed a significantly positive relationship in all groups (r = 0.594; P = .002).

CONCLUSIONS

Analysis of the Doppler flow SPV and VrPV, the VrPV/SPV ratio, and the diameter of the SVC might provide an alternative method for catheterization in estimating pulmonary pressure.