Younger age at initiation of subcutaneous treprostinil is associated with better response in pediatric Group 1 pulmonary arterial hypertension.

Children with severe Group 1 pulmonary arterial hypertension (PAH) have an unpredictable response to subcutaneous treprostinil (TRE) therapy, which may be influenced by age, disease severity, or other unknown variables at time of initiation. In this retrospective single-center cohort study, we hypothesized that younger age at TRE initiation, early hemodynamic response (a decrease in pulmonary vascular resistance by ≥30% at follow-up catheterization), and less severe baseline hemodynamics (Rp:Rs < 1.1) would each be associated with better clinical outcomes. In 40 pediatric patients with Group I PAH aged 17 days-18 years treated with subcutaneous TRE, younger age (cut-off of 6-years of age, AUC 0.824) at TRE initiation was associated with superior 5-year freedom from adverse events (94% vs. 39%, p = 0.002), better WHO functional class (I or II: 88% vs. 39% p = 0.003), and better echocardiographic indices of right ventricular function at most recent follow-up. Neither early hemodynamic response nor less severe baseline hemodynamics were associated with better outcomes. Patients who did not have a significant early hemodynamic response to TRE by first follow-up catheterization were unlikely to show subsequent improvement in PVRi (1/8, 13%). These findings may help clinicians counsel families and guide clinical decision making regarding the timing of advanced therapies.

Failure to tolerate continuous subcutaneous treprostinil in pediatric pulmonary hypertension patients.

Continuous subcutaneous (SubQ) treprostinil is an effective therapy for pediatric patients diagnosed with pulmonary hypertension (PH). To date, the clinical characteristics and factors associated with failure to tolerate this therapy have not been described. The purpose was to describe patient-reported factors contributing to SubQ treprostinil intolerance in pediatric patients with PH. A retrospective descriptive study was performed at 11 participating sites in the United States and Canada for patients younger than 21 years of age diagnosed with PH who failed treatment to tolerate SubQ treprostinil between January 1, 2009, and December 31, 2019. All data were summarized using descriptive statistics. Forty-one patients met the inclusion criteria. The average age at SQ treprostinil initiation, and length of treatment, was 8.6 years and 22.6 months, respectively. The average maximum dose, concentration, and rate were 95.8 ng/kg/min, 6.06 mg/mL, and 0.040 mL/h, respectively. The reasons for failure to tolerate SubQ treprostinil included intractable site pain (73.2%), frequent site changes (56.1%), severe site reactions (53.7%), infections (26.8%), and noncompliance/depression/anxiety (17.1%). Thirty-nine (95.1%) patients transitioned to a prostacyclin therapy with 23 patients transitioning to intravenous prostacyclin, 5 to inhaled prostacyclin, 5 to oral prostacyclin, and 7 to a prostacyclin receptor agonist. A subset of pediatric PH patients failed to tolerate SubQ treprostinil infusions despite advances in SubQ site maintenance and pain management strategies. Intractable site pain, frequent SubQ site changes, and severe localized skin reactions were the most common reasons for failure.

Subcutaneous Treprostinil Improves Surgical Candidacy for Next Stage Palliation in Single Ventricle Patients With High-Risk Hemodynamics.

Single ventricle (SV) patients with pulmonary vascular disease (SV-PVD) are considered poor surgical candidates for Glenn or Fontan palliation. Given limited options for Stage 1 (S1) and Stage 2 (S2) SV patients with SV-PVD, we report on the use of subcutaneous treprostinil (TRE) to treat SV-PVD in this population. This single-center, retrospective cohort study examined SV patients who were not candidates for subsequent surgical palliation due to SV-PVD and were treated with TRE. The primary outcome was ability to progress to the next surgical stage; secondary outcomes included changes in hemodynamics after TRE initiation. Between 3/2014 and 8/2021, 17 SV patients received TRE for SV-PVD: 11 after S1 and 6 after S2 (median PVR 4.1 [IQR 3.2-4.8] WU*m2 and 5.0 [IQR 1.5-6.1] WU*m2, respectively). Nine of 11 (82%) S1 progressed to S2, and 2 (18%) underwent heart transplant (HTx). Three of 6 (50%) S2 progressed to Fontan, 1 underwent HTx and 2 are awaiting Fontan on TRE. TRE significantly decreased PVR in S1 patients with median post-treatment PVR of 2.0 (IQR 1.5-2.6) WU*m2. TRE can allow for further surgical palliation in select pre-Fontan patients with SV-PVD, obviating the need for HTx. Improvement in PVR was significant in S1 patients and persisted beyond discontinuation of therapy for most patients.

Abnormal platelet aggregation in pediatric pulmonary hypertension.

Endogenous prostacyclin stimulates pulmonary vasodilation and inhibits platelet aggregation. For the synthetic analog treprostinil, used in the treatment of pulmonary hypertension (PH), conflicting, anecdotal evidence exists regarding its effects on clinically relevant platelet function. This study investigated whether treprostinil therapy results in inhibition of platelet aggregation in pediatric PH patients. This is a single institution, prospective, cohort study. Pediatric patients ≤18 years of age on medical therapy for PH underwent platelet function testing by light transmission aggregometry with U-46619-a stable analog of endoperoxide prostaglandin H2, exhibiting properties similar to thromboxane A2 (TXA2). Results were compared for those on continuous treprostinil therapy (TRE) versus those on other, non-prostacyclin therapies (non-TRE). Thirty-five patients were enrolled: 18 in the TRE group and 17 in the non-TRE group. There was no difference in platelet aggregation abnormalities between the two groups: 44% (n = 8) in the TRE group and 41% (n = 7) in the non-TRE group were abnormal. Furthermore, subgroup analysis showed no difference based on treprostinil dosing. This study demonstrated similar, moderately high rates of abnormal platelet aggregation in pediatric PH patients on continuous treprostinil therapy compared to those on other, non-prostacyclin therapies. The high rate of abnormal platelet aggregation in the entire cohort, however, warrants follow-up study to identify a potential inherent risk in this population.

Treprostinil improves hemodynamics and symptoms in children with mild pulmonary hypertension awaiting heart transplantation.

BACKGROUND: Treprostinil, a prostacyclin analog, is a safe and effective therapy for children with PAH; however, the use of this agent in children with mild PVR elevations related to HF, including those with SV congenital heart disease awaiting HT, is understudied. We describe the hemodynamic and symptomatic changes in pediatric patients awaiting HT treated with treprostinil. METHODS: Single-center retrospective review of all patients was listed for HT who received treprostinil during the listing period. Changes in hemodynamic and functional indices between the baseline catheterization (prior to drug initiation), and prior to HT, and patient outcomes were analyzed. RESULTS: Among 16/17 (94%) who survived to HT, 8 (50%) were female, and 10 (63%) had SV physiology. The median age at drug initiation was 9 (IQR: 1, 14) years. The median duration of therapy prior to HT was 253 (IQR: 148, 504) days. Treprostinil significantly decreased PVR (3.8 vs 3.1 WU, P = .03), while mLA or mPCW pressure did not change (11 vs 13 mm Hg, P = .9). HF symptoms improved in 9/15 (60%) patients without VAD support prior to drug initiation, including 4/10 (40%) who did not receive a VAD any point while awaiting HT. CONCLUSIONS: Treprostinil may be used safely in patients with mild PAH awaiting HT, including those with SV disease. PVR falls without substantial increases in mLA/mPCW pressure. HF symptoms improve in some patients.

Subcutaneous and Intravenous Treprostinil Pharmacokinetics in Children With Pulmonary Vascular Disease.

This study evaluated the pharmacokinetics of intravenous (IV) and subcutaneous (SC) treprostinil in pediatric patients with pulmonary vascular disease, and compared them with existing adult data from a similar cohort. Blood samples were collected from pediatric patients receiving steady-state IV or SC treprostinil and were assessed for plasma treprostinil concentration using liquid chromatography and tandem mass spectrometry. Forty participants, 15 receiving IV and 25 receiving SC treprostinil, were included in the analysis. Age ranged from 0.1 to 15.6 years. The median dose of treprostinil was 45.5 ng·kg·min with a range of 8-146 ng·kg·min. There was a linear relationship between treprostinil dose and plasma concentration with an R of 0.57. On average, there were higher blood concentrations per given dose of IV treprostinil compared with those per given dose of SC, but the difference was not significant. Compared with adult data, the slope of the pediatric data was similar, but the y-intercept was significantly lower. Additionally, the concentration per dose ratio was significantly higher in adults compared with children. Pediatric patients have significantly lower average blood concentrations of treprostinil per given dose compared with adults, and higher, but not significantly so, blood concentrations when treprostinil is administered IV as compared with SC administration.

Right ventricular stroke work correlates with outcomes in pediatric pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) is characterized by elevated pulmonary artery pressures (PAP) and pulmonary vascular resistance (PVR). Optimizing treatment strategies and timing for transplant remains challenging. Thus, a quantitative measure to predict disease progression would be greatly beneficial in treatment planning. We devised a novel method to assess right ventricular (RV) stroke work (RVSW) as a potential biomarker of the failing heart that correlates with clinical worsening. Pediatric patients with idiopathic PAH or PAH secondary to congenital heart disease who had serial, temporally matched cardiac catheterization and magnetic resonance imaging (MRI) data were included. RV and PA hemodynamics were numerically determined by using a lumped parameter (circuit analogy) model to create pressure-volume (P-V) loops. The model was tuned using optimization techniques to match MRI and catheterization derived RV volumes and pressures for each time point. RVSW was calculated from the corresponding P-V loop and indexed by ejection fraction and body surface area (RVSWEF) to compare across patients. Seventeen patients (8 boys; median age = 9.4 years; age range = 4.4-16.3 years) were enrolled. Nine were clinically stable; the others had clinical worsening between the time of their initial matched studies and their most recent follow-up (mean time = 3.9 years; range = 1.1-8.0 years). RVSWEF and the ratio of pulmonary to systemic resistance (Rp:Rs) values were found to have more significant associations with clinical worsening within one, two, and five years following the measurements, when compared with PVR index (PVRI). A receiver operating characteristic analysis showed RVSWEF outperforms PVRI, Rp:Rs and ejection fraction for predicting clinical worsening. RVSWEF correlates with clinical worsening in pediatric PAH, shows promising results towards predicting adverse outcomes, and may serve as an indicator of future clinical worsening.

Central line replacement following infection does not improve reinfection rates in pediatric pulmonary hypertension patients receiving intravenous prostanoid therapy.

Treatment of pediatric pulmonary hypertension (PH) with IV prostanoids has greatly improved outcomes but requires a central line, posing inherent infection risk. This study examines the types of infections, infection rates, and importantly the effect of line management strategies on reinfection in children receiving IV prostanoids for PH. This study is a retrospective review of all pediatric PH patients receiving intravenous epoprostenol (EPO) or treprostinil (TRE) at one academic tertiary care center between 2000 and 2014. No patients declined participation in the study or were otherwise excluded. Infectious complications were characterized by organism(s), infection rates, time to next infection, and line management decisions (salvage vs. replace). Of the 40 patients followed, 13 sustained 38 infections involving 49 pathogens, with a predominance of gram-positive (GP) organisms (n = 35). The pooled infection rate was 1.06 per 1000 prostanoid days with no difference between EPO and TRE. No significant difference in reinfection rate was observed when comparing line salvage to replacement, regardless of organism type. Both overall and organism-type comparisons suggest longer time between line infections following line salvage compared with line replacement (732 vs. 410 days overall; 793 vs. 363 days for GP; 611 vs. 581 days for gram-negative [GN]; P > 0.05 for all comparisons). Central line replacement following blood stream infections in pediatric PH patients does not improve subsequent infection rates or time to next infection, and may lead to unnecessary risks associated with line replacement, including potential loss of vascular access. A revised approach to central line infections in pediatric PH is proposed.

Hemodynamic Effects of Phenylephrine, Vasopressin, and Epinephrine in Children With Pulmonary Hypertension: A Pilot Study.

OBJECTIVES: During a pulmonary hypertensive crisis, the marked increase in pulmonary vascular resistance can result in acute right ventricular failure and death. Currently, there are no therapeutic guidelines for managing an acute crisis. This pilot study examined the hemodynamic effects of phenylephrine, arginine vasopressin, and epinephrine in pediatric patients with pulmonary hypertension. DESIGN: In this prospective, open-label, nonrandomized pilot study, we enrolled pediatric patients previously diagnosed with pulmonary hypertensive who were scheduled electively for cardiac catheterization. Primary outcome was a change in the ratio of pulmonary-to-systemic vascular resistance. Baseline hemodynamic data were collected before and after the study drug was administered. PATIENTS: Eleven of 15 participants were women, median age was 9.2 years (range, 1.7-14.9 yr), and median weight was 26.8 kg (range, 8.5-55.2 kg). Baseline mean pulmonary artery pressure was 49 ± 19 mm Hg, and mean indexed pulmonary vascular resistance was 10 ± 5.4 Wood units. Etiology of pulmonary hypertensive varied, and all were on systemic pulmonary hypertensive medications. INTERVENTIONS: Patients 1-5 received phenylephrine 1 µg/kg; patients 6-10 received arginine vasopressin 0.03 U/kg; and patients 11-15 received epinephrine 1 µg/kg. Hemodynamics was measured continuously for up to 10 minutes following study drug administration. MEASUREMENTS AND MAIN RESULTS: After study drug administration, the ratio of pulmonary-to-systemic vascular resistance decreased in three of five patients receiving phenylephrine, five of five patients receiving arginine vasopressin, and three of five patients receiving epinephrine. Although all three medications resulted in an increase in aortic pressure, only arginine vasopressin consistently resulted in a decrease in the ratio of systolic pulmonary artery-to-aortic pressure. CONCLUSIONS: This prospective pilot study of phenylephrine, arginine vasopressin, and epinephrine in pediatric patients with pulmonary hypertensive showed an increase in aortic pressure with all drugs although only vasopressin resulted in a consistent decrease in the ratio of pulmonary-to-systemic vascular resistance. Studies with more subjects are warranted to define optimal dosing strategies of these medications in an acute pulmonary hypertensive crisis.

Reported sildenafil side effects in pediatric pulmonary hypertension patients.

BACKGROUND: Sildenafil, a phosphodiestase type 5 inhibitor, was approved in 2005 for the treatment of pulmonary arterial hypertension (PAH) in adults and is commonly used off-label for pediatric patients. Little is known, however, about sildenafil's side effects in this population. METHODS: Single institution, longitudinal survey-based study performed in an outpatient pediatric cardiology clinic. Pediatric patients on sildenafil [alone or in combination with other pulmonary hypertension (PH) therapies] completed questionnaires regarding frequency of vascular, gastrointestinal, neurologic, and hematologic side effects. RESULTS: Between January 2011 and May 2014, 66 pediatric patients with PH on sildenafil filled out 214 surveys, 32 patients (96 surveys) on monotherapy, and 43 patients (118 surveys) on sildenafil plus an endothelin receptor antagonist (ERA) (bosentan or ambrisentan) and/or a prostacyclin (epoprostenol or treprostinil). Overall, 30% of respondents identified at least one side effect. For all patients on sildenafil, incidence of side effects by system was 37% gastrointestinal, 35% vascular, and 22% neurologic. For patients on sildenafil monotherapy, incidence of side effects by system was 24% gastrointestinal, 21% vascular, and 18% neurologic compared to patients on combination therapy who reported an incidence of 48% gastrointestinal, 45% vascular, and 25% neurologic. CONCLUSION: Incidence of vascular, gastrointestinal, and neurologic side effect in pediatric patients on sildenafil therapy for PAH was 30%. Side effects were more common in patients on combination therapy with an ERA and/or prostacyclin than in patients on sildenafil monotherapy.

Magnetic resonance imaging of the right ventricle in pediatric pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) causes changes in the right ventricle (RV), affecting RV size and function, ultimately leading to death. These changes have been evaluated by cardiac MRI (CMR) in adults with PAH, but not in children. Using CMR in pediatric patients with PAH, we examined how RV size and function (1) compare to normal data, (2) change over time, and (3) compare to similar studies in the adult population. Data from two institutions were retrospectively reviewed. Subjects with PAH and a CMR were included. Baseline CMR variables (right and left ventricular end-diastolic and end-systolic volumes indexed for body surface area, and calculated stroke volume and ejection fraction) were compared to normative data and follow-up CMR data. Twenty-six subjects (15 female), age 2-16 (mean 11) years, with idiopathic PAH were included. All patients were on PAH medication, and 65% on prostacyclin therapy. The baseline 6-Minute Walk Distance (6MWD; 481 ± 137) was normal. RV volumes and ejection fraction were markedly abnormal compared to normal data (P < 0.001). Follow-up CMRs were analyzed in 15 patients. RV volumes and function and LV stroke volume showed no significant change over one year. Our pediatric patients with PAH have markedly abnormal right ventricles by CMR but have normal walk distances. The lack of change in CMR parameters over one year may represent a stable cohort and is different than similar studies in adults.

Children with pulmonary arterial hypertension and prostanoid therapy: long-term hemodynamics.

BACKGROUND: Pediatric patients with severe pulmonary arterial hypertension (PAH) are treated with intravenous epoprostenol or intravenous or subcutaneous treprostinil. Little is known about longitudinal hemodynamics and outcomes of epoprostenol, treprostinil, and transitions from epoprostenol to treprostinil. METHODS: This was retrospective study of 77 pediatric patients (47 idiopathic PAH, 24 congenital heart disease-PAH) receiving epoprostenol or treprostinil from 1992 to 2010 at 2 centers. Outcomes were defined as living vs dead/transplant. RESULTS: Mean age at baseline was 7.7 ± 5.2 years, with follow-up of 4.3 ± 3.4 years. Thirty-seven patients were treated with epoprostenol, 20 with treprostinil, and 20 were transitioned from epoprostenol to treprostinil. Mean pulmonary-to-systemic vascular resistance ratio (Rp/Rs) for epoprostenol was 1.0 ± 0.4, 0.8 ± 0.4, 0.8 ± 0.4, 1.0 ± 0.4, and 1.2 ± 0.4, respectively, at baseline, 1, 2, 3, and 4 years. For treprostinil, Rp/Rs was 0.9 ± 0.3, 0.7 ± 0.3, 0.5 ± 0.2, (p < 0.01 vs baseline), and 1.1 ± 0.2, respectively, at baseline, 1, 2, and 3 to 4 years, respectively. There were similar changes in mean pulmonary artery pressure and pulmonary vascular resistance index. The Rp/Rs 1 year after epoprostenol to treprostinil transition increased from 0.6 to 0.8 (n = 7). Changes not statistically significant unless noted. Eight patients died or received a transplant within 2 years of baseline; compared with the rest of the cohort, mean baseline Rp/Rs, right atrial pressure, and pulmonary vascular resistance index were significantly worse in this group. Thirty-nine patients remain on prostanoids, 17 are off, 16 died, and 5 received heart-lung transplant. Kaplan-Meier 5-year transplant-free survival was 70% (95% confidence interval, 56%-80%). CONCLUSION: There was improvement in Rp/Rs on both therapies at 1 to 2 years that was not sustained. The 5-year transplant-free survival was better than in similar adult studies.

Food and Drug Administration (FDA) postmarket reported side effects and adverse events associated with pulmonary hypertension therapy in pediatric patients.

Because most medications for pediatric pulmonary hypertension (PH) are used off label and based on adult trials, little information is available on pediatric-specific adverse events (AEs). Although drug manufacturers are required to submit postmarket AE reports to the Food and Drug Administration (FDA), this information is rarely transmitted to practitioners. In the setting of a recent FDA warning for sildenafil, the authors sought to give a better description of the AEs associated with current therapies in pediatric PH. In January 2010, a written request was made to the Food and Drug Administration for AE records of commonly used PH medications. Reports were screened for pediatric patients, analyzed in terms of AEs, and compared with the medical literature. Arbitrarily, AEs that could be attributed to concomitant medications were not attributed to the PH medication in question. Adverse events occurring in more than 5 % of events for each drug were assumed to be associated with the targeted PH medication. Between November 1997 and December 2009, 588 pediatric AE reports (death in 257 cases) were reported for the three most commonly used therapies: bosentan, epoprostenol, and sildenafil. Many of the AEs were similar to those reported previously. However, 27 AEs not previously reported in the literature (e.g., pulmonary hemorrhage, hemoptysis, and pneumonia) were found. The FDA postmarket records for PH medications in pediatric patients show a significant number of AEs. The discovery of AEs not previously reported will better inform those caring for these complex and critically ill children, and the large number of deaths suggest they may be underreported in current literature.