Trends in transcatheter and operative closure of patent ductus arteriosus in neonatal intensive care units: Analysis of data from the Pediatric Health Information Systems Database

Who Still Gets Ligated? Reasons for Persistence of Surgical Ligation of the Patent Ductus Arteriosus Following Availability of Transcatheter Device Occlusion for Premature Neonates

(1) Background: To identify reasons for the persistence of surgical ligation of the patent ductus arteriosus (PDA) in premature infants after the 2019 Food and Drug Administration (FDA) approval of transcatheter device closure; (2) Methods: We performed a 10-year (2014-2023) single-institution retrospective study of premature infants (<37 weeks) and compared clinical characteristics and neonatal morbidities between neonates that underwent surgical ligation before (epoch 1) and after (epoch 2) FDA approval of transcatheter closure; (3) Results: We identified 120 premature infants that underwent surgical ligation (n = 94 before, n = 26 after FDA approval). Unfavorable PDA morphology, active infection, and recent abdominal pathology were the most common reasons for surgical ligation over device occlusion in epoch 2. There were no differences in demographics, age at closure, or outcomes between infants who received surgical ligation in the two epochs; (4) Conclusions: Despite increasing trends for transcatheter PDA closure in premature infants, surgical ligation persists due to unfavorable ductal morphology, active infection, or abdominal pathology.

Incidence, Management, and Outcomes of Pulmonary Embolism at Tertiary Pediatric Hospitals in the United States

Background

Pediatric pulmonary embolism (PE) is rare and potentially life-threatening. Though thrombolysis and thrombectomy are increasingly used in adult PE, trends in pediatric treatment and outcomes remain incompletely described.

Objectives

The purpose of this study was to describe the incidence of PE, proportion of cases treated with anticoagulation alone, systemic thrombolysis, and directed therapy (local thrombolysis and thrombectomy), clinical outcomes, and total costs.

Methods

A multicenter observational study was performed using administrative data from the Pediatric Health Information System database to study PE treated at U.S. pediatric hospitals from 2015 to 2021. Outcomes by treatment were evaluated using multivariable generalized linear mixed effects models.

Results

Of 3,136 subjects, 70% were at least 12 years of age, and 46% were male. Sixty-two percent had at least 1 comorbidity, and congenital heart disease of any kind was the most prevalent (20%). Eighty-eight percent of subjects received anticoagulation alone, 7% received systemic thrombolysis, and 5% received directed therapy. Overall in-hospital mortality was 7.5%. Treatment approach did not change over time (P = 0.98). After adjusting for patient characteristics, directed therapy was associated with a lower risk of mortality (adjusted percentage -3%, [95% CI: -5% to 0%]) than anticoagulation alone. Systemic thrombolysis was associated with a greater total cost of hospitalization ($113,043 greater [95% CI: $62,866, $163,219]). Length of hospital stay did not differ by treatment.

Conclusions

Pediatric patients with PE have a high incidence of underlying chronic disease. Anticoagulation alone remains the mainstay of treatment, with thrombolysis and thrombectomy rarely being used. Given the relative rarity of pediatric PE, additional research requiring innovative study designs is paramount.

Current Trends in Invasive Closure of Patent Ductus Arteriosus in Very Low Birth Weight Infants in United States Children's Hospitals, 2016-2021

OBJECTIVE

To describe the current practices in invasive patent ductus arteriosus (PDA) closure (surgical ligation or transcatheter occlusion) in very low birth weight (VLBW) infants and changes in patient characteristics and outcomes from 2016 to 2021 among US children's hospitals.

STUDY DESIGN

We evaluated a retrospective cohort of VLBW infants (birth weight 400-1499 g and gestational age 22-31 weeks) who had invasive PDA closure within 6 months of age from 2016 to 2021 in children's hospitals in the Pediatric Health Information System. Changes in patient characteristics and outcomes over time were evaluated using generalized linear models and generalized linear mixed models.

RESULTS

2418 VLBW infants (1182 surgical ligation; 1236 transcatheter occlusion) from 42 hospitals were included. The proportion of infants receiving transcatheter occlusion increased from 17.2% in 2016 to 84.4% in 2021 (P < .001). In 2021, 28/42 (67%) hospitals had performed transcatheter occlusion in > 80% of their VLBW infants needing invasive PDA closure, compared with only 2/42 (5%) in 2016. Although median postmenstrual age (PMA) at PDA closure did not change for the overall cohort, PMA at transcatheter occlusion decreased from 38 weeks in 2016 to 31 weeks by 2020, P < .001. Among those infants not intubated prior to PDA closure, extubation within 3 days postprocedure increased over time (yearly adjusted odds ratios of 1.26 [1.08-1.48]). Length of stay and mortality did not change over time.

CONCLUSION

We report rapid adoption of transcatheter occlusion for PDA among VLBW infants in US children's hospitals over time. Transcatheter occlusions were performed at younger PMA over time.

Comparative Effectiveness of Surgical Ligation and Catheter Closure of Patent Ductus Arteriosus in Preterm Infants

To evaluate the association, if any, between closure modality (surgical ligation SL vs. catheter CC) of a hemodynamically significant patent ductus arteriosus (PDA), after failure of or contraindication to medical therapy, and immediate procedural complications, and post-procedure physiologic status in preterm (gestational age < 32 weeks) infants. In this single-center retrospective cohort study, data were accessed on infants < 32 weeks gestation, who underwent SL or CC of PDA, born from 2019-2021. The choice of modality was determined by parents, after they were provided information on both procedures. Our cohort (n = 112) included 36 (32.1%) infants who underwent SL while 76 (67.9%) underwent CC. The SL group of infants were significantly more immature at birth, younger on admission to the level IV NICU and received more mean (SD) surfactant doses than the CC group. Higher proportions of infants in the SL group had 5-min Apgar scores ≤ 5, seizures, severe intracranial hemorrhage and had received medical therapy for PDA. Both procedures were highly efficacious, with 1 unsuccessful device placement attempt and had low associated adverse events. Two (2.6%) infants had device migration 24 h after CC. SL was associated with a higher rate of immediate postoperative hypothermia whereas, in the CC group, mean airway pressure was significantly lower 48 h after, compared to before the procedure. SL and CC are comparable in short-term efficacy and safety for PDA closure. Long-term outcomes data are needed following both procedures.

Hospital variation in neonatal echocardiography among very preterm infants at US children's hospitals

OBJECTIVE

Estimate hospital variation in echocardiography (echo) among very preterm infants.

STUDY DESIGN

Retrospective cohort study of very preterm (<32 weeks) infants discharged between 2012 and 2019 from US children's hospitals. Echo exposure was identified using daily billing, and hospital variation was estimated after adjustment for illness severity. Variation in very early echo use (<3 days of life) was compared to exposure to treatment of a patent ductus arteriosus (PDA), and other practice patterns.

RESULTS

27,498 subjects across 39 children's hospitals were included. Very early echo use had the greatest hospital variation (3-34%). Increasing very early echo use was not associated with PDA treatment (p = 0.93), but was associated with nitric oxide (p < 0.01) and vasoactive medications (p < 0.01).

CONCLUSIONS

Hospital variation in echo use among preterm infants was greatest in the first few days of life and was associated with increasing nitric oxide and vasoactive medication use. The impact of this variation on clinical outcomes is uncertain and warrants further investigation.

Renal Function After Transcatheter Piccolo Patent Ductus Arteriosus Closure With Contrast Angiography in Extremely Premature Infants

Transcatheter patent ductus arteriosus (PDA) device closure is increasingly performed in extremely premature infants. Contrast angiography improves the procedural safety and effectiveness by precise anatomic delineation. Contrast nephropathy is a concern in clinically ill premature infants, especially with the presence of renal insufficiency. We hypothesized that the benefit of transcatheter PDA closure outweighs the harm of contrast nephropathy in extremely premature infants. A total of 160 infants underwent successful transcatheter (n = 59) and surgical (n = 101) PDA closure at a median age of 26 (7 to 78) days. The surgical group had a lower procedural weight (870 vs 960 g, p = 0.014). In the transcatheter group, serum creatinine decreased from 0.48 to 0.45 mg/100 ml at 24 hours (p = 0.003, n = 59) and decreased further to 0.37 mg/100 ml at 5 to 7 days after closure (p <0.001). Median contrast amount was 1.9 ml/kg (0.6 to 6.1). In 8 infants with pre-existing renal insufficiency who underwent transcatheter closure, serum creatine significantly improved from 1.44 to 1.36 mg/100 ml at 24 hours and 0.79 mg/100 ml at 5 to 7 days after closure (p <0.001). There was no difference in improvement of serum creatinine between transcatheter and surgical closure groups. In conclusion, despite the use of contrast, serum creatinine significantly improved with transcatheter PDA closure even in infants with pre-existing renal insufficiency. Contrast angiography should not be discouraged for transcatheter PDA closure because of the concern for contrast nephropathy in extremely premature infants.

Prevalent pharmacotherapy of US Fontan survivors: A study utilizing data from the MarketScan Commercial and Medicaid claims databases

BACKGROUND

Survivors of Fontan palliation are at life-long risk of thrombosis, arrhythmia, and circulatory failure. To our knowledge, no studies have evaluated current United States pharmaceutical prescription practice in this population.

METHODS

A retrospective observational study evaluating the prevalent use of prescription medications in children and adolescents with hypoplastic left heart syndrome or tricuspid atresia after Fontan completion (identified using ICD9/10 codes) was performed using data contained in the MarketScan Commercial and Medicaid databases for the years 2013 through 2018. Cardiac pharmaceuticals were divided by class. Anticoagulant agents other than platelet inhibitors, which are not uniformly a prescription medication, were also studied. Associations between increasing age and the likelihood of a filled prescription for each class of drug were evaluated. Annualized retail costs of pharmaceutical regimens were calculated.

RESULTS

A cohort of 4,056 subjects (median age 12 years [interquartile range: 8-16], 61% male, 60% commercial insurance) was identified. Of the cohort, 50% received no prescription medications. Angiotensin converting enzyme inhibitors/angiotensin receptor blockers (ACEi/ARB) (38%), diuretics (15%), and mineralocorticoid receptor antagonists (8%) were prescribed with the highest frequency. Pulmonary vasodilators were received by 6% of subjects. Older age was associated with increased likelihood of filled prescriptions for anticoagulants (P = .008), antiarrhythmic agents, digoxin, ACEi/ARB, and beta blockers (each P < .0001), but also lower likelihood of filled prescriptions for pulmonary vasodilators, conventional diuretics (both P < .0001), and mineralocorticoid receptor antagonists (P = .02).

CONCLUSIONS

Pharmaceuticals typically used to treat heart failure and pulmonary hypertension are the most commonly prescribed medications following Fontan palliation. While the likelihood of treatment with a particular class of medication is associated with the age of the patient, determining the optimal regimen for individual patients and the population at large is an important knowledge gap for future research.

Trend and Outcomes for Surgical Versus Transcatheter Patent Ductus Arteriosus Closure in Neonates and Infants at US Children's Hospitals

Background Pharmacologic therapy for patent ductus arteriosus closure is not consistently successful. Surgical ligation (SL) or transcatheter closure (TC) may be needed. Large multicenter analyses comparing outcomes and resource use between SL and TC are lacking. We hypothesized that patients undergoing TC have improved outcomes compared with SL, including mortality, hospital and intensive care unit length of stay, and mechanical ventilation. Methods and Results Using the 2016 to 2020 Pediatric Health Information System database, characteristics, outcomes, and charges of patients aged <1 year who underwent TC or SL were analyzed. A total of 678 inpatients undergoing TC (n=503) or SL (n=175) were identified. Surgical patients were younger (0.1 versus 0.53 years; P<0.001) and more premature (60% versus 20.3%; P<0.001). Surgical patients had higher mortality (1.7% versus 0%; P=0.02). Using inverse probability of treatment weighting by the propensity score, multivariable-adjusted analyses demonstrated favorable outcomes in TC: intensive care unit admission rates (adjusted odds ratio [OR], 0.2; 95% CI, 0.11-0.32; P<0.001); mechanical ventilation rates (adjusted OR, 0.3; 95% CI, 0.19-0.56; P<0.001); and shorter hospital (adjusted coefficient, 2 days shorter; 95% CI, 1.3-2.7; P<0.001) and postoperative (adjusted coefficient, 1.2 days shorter; 95% CI, 0.1-2.3; P=0.039) stays. Overall charges and readmission rates were similar. Among premature neonates and infants, hospital (adjusted difference in medians, 4 days; 95% CI, 1.7-6.3 days; P<0.001) and postoperative stays (adjusted difference in medians, 3 days; 95% CI, 1.1-4.9 days; P=0.002) were longer for SL. Conclusions TC is associated with lower mortality and reduced length of stay compared with SL. Rates of TC continue to increase compared with SL.

Near-infrared spectroscopy for perioperative assessment and neonatal interventions

Perioperative applications of near-infrared spectroscopy (NIRS) to monitor regional tissue oxygenation and perfusion in cardiac and noncardiac surgery are of increasing interest in neonatal care. Complex neonatal surgery can impair adequate oxygen delivery and tissue oxygen consumption and increase the risk of neurodevelopmental delay. Coupled with conventional techniques, NIRS monitoring may enable targeted hemodynamic management of the circulation in both cardiac and noncardiac surgical procedures. In this narrative review, we discuss the application of perioperative NIRS in specific neonatal interventions, including surgical intervention for congenital heart defects, definitive closure of the patent ductus arteriosus, neurological and gastrointestinal disorders, and use of extracorporeal membrane oxygenation. We identified areas for future research within disease-specific indications and offer a roadmap to aid in developing evidence-based targeted diagnostic and management strategies in neonates. IMPACT: There is growing recognition that perioperative NIRS monitoring, used in conjunction with conventional monitoring, may provide critical hemodynamic information that either complements clinical impressions or delivers novel physiologic insight into the neonatal circulatory and perfusion pathways.

Change and clinical significance of serum cortisol, BNP, and PGE-2 levels in premature infants with patent ductus arteriosus

BACKGROUND

To analyze the change and clinical significance of cortisol, B-type brain natriuretic peptide (BNP), and prostacyclin-2 (PGE-2) levels in premature infants with patent ductus arteriosus (PDA).

METHODS

A total of 67 cases of premature infants admitted to our hospital from January 2018 to April 2020 were included, all of whom developed PDA (PDA group). According to the presence or absence of symptoms, they were divided into the symptomatic group (28 cases) and the asymptomatic group (39 cases). In addition, 62 premature infants without PDA who were born in our hospital during the same period were selected as the control group. The expression levels of cortisol, BNP, and PGE-2 in infants in different groups and between infants with symptoms and without symptoms were analyzed, along with the risk factors leading to PDA in preterm infants. The value of cortisol, BNP, and PGE-2 in the diagnosis of PDA in premature infants was also analyzed.

RESULTS

Compared with the control group, cortisol in the PDA group was significantly decreased (P<0.05), while the levels of BNP and PGE-2 were significantly increased (P<0.05). The cortisol level in the asymptomatic group was significantly higher than that in the symptomatic group, while the levels of BNP and PGE-2 were opposite, and the differences were statistically significant (P<0.05). Logistic regression analysis showed that birth weight <1,200 g, decreased cortisol, increased BNP, and increased PGE-2 were independent risk factors leading to PDA in preterm infants, and the differences were statistically significant (P<0.05). Receiver operating characteristic (ROC) curve showed that the sensitivity and specificity of cortisol+BNP+PGE-2 in the diagnosis of PDA in premature infants were 75.60% and 73.10%, respectively. The area under the curve (AUC) value was 0.759 (95% CI: 0.611-0.859), which was significantly higher than the AUC values of the 3 tests alone (P<0.05).

CONCLUSIONS

The expression of cortisol decreased in premature infants with PDA, while the levels of BNP and PGE-2 significantly increased. Dynamic detection of the changes in these levels can provide an important reference for the early diagnosis of PDA and for the assessment of disease progression.

Distensibility of the ductus arteriosus in neonates and young infants undergoing transcatheter closure

Device migration is one of serious complications in neonates and infants undergoing transcatheter closure of the patent ductus arteriosus (PDA). We hypothesize that neonates and young infants possess the distensibility of the ductus, which may be related to device migration. We retrospectively reviewed angiographic findings in 41 neonates and infants who underwent transcatheter closure of PDA. We measured diameters of the ductus at the pulmonary (PA) side, the center, and the aortic (AO) side before PDA closure, and the device center diameter after device closure. The distensibility index was defined as the ratio of the device center diameter after device deployment to the diameter at the center of the ductus before PDA closure. Age and weight at the procedure were 168 (117-260) days and 5.3 (4.3-6.9) kg, respectively. Thirty-seven subjects accomplished the successful device closure, and four subjects were declined because of the device instability or migration. Implanted devices included Amplatzer Duct Occluders in 33 subjects and Amplatzer Vascular Plug-2 in 8 subjects. The PDA diameters at PA side, at the center, AO side, and the device center diameter were 3.2 (2.2-4.3) mm, 4.7 (3.6-5.7) mm, 7.7 (6.3-9.4) mm, and 5.8 (4.2-6.9) mm, respectively. The PDA diameter before closure was not correlated age and weight. The distensibility index was 1.28 (1.06-1.64), which was significantly correlated to age (r = - 0.49, P = 0.001) and weight (r = - 0.53, P < 0.001). Infants with the younger age and the lower weight have the more distensible PDA, which may be a risk for device migration.

Discharge of Medically Complex Infants and Developmental Follow-up

At the time of discharge from the NICU, many infants have ongoing complex medical issues that will require coordinated, multispecialty follow-up. Discharge planning and transfer of care for infants with medical complexity require a multidisciplinary team effort that begins early during the NICU hospitalization. It is critical that the primary care physician is involved in this process because he or she will serve as the chief communicator and coordinator of care after discharge. Although some infants with medical complexity may be followed in specialized multidisciplinary NICU follow-up clinics, these are not universally available. The responsibility then falls to the primary care physician to coordinate with different subspecialties based on the infant's needs. Many infants with medical complexity are technology-dependent at the time of discharge and may require home oxygen, ventilators, monitors, or tube feeding. Prematurity, critical illness, and prolonged NICU hospitalization that lead to medical complexity also increase the risk of neurodevelopmental delay or impairment. As such, these infants will not only require routine developmental surveillance and screening by the primary care physician but also should be followed longitudinally by a neurodevelopmental specialist, either a developmental-behavioral pediatrician or a neonatologist with experience in neurodevelopmental assessment.

Trends in Discharge Prescription of Digoxin After Norwood Operation: An Analysis of Data from the Pediatric Health Information System (PHIS) Database

Quality improvement efforts have focused on reducing interstage mortality for infants with hypoplastic left heart syndrome (HLHS). In 1/2016, two publications reported that use of digoxin was associated with reduced interstage mortality. The degree to which these findings have affected real world practice has not been evaluated. The discharge medications of neonates with HLHS undergoing Norwood operation between 1/2007 and 12/2018 at Pediatric Health Information Systems Database hospitals were studied. Mixed effects models were calculated to evaluate the hypothesis that the likelihood of digoxin prescription increased after 1/2016, adjusting for measurable confounders with furosemide and aspirin prescription measured as falsification tests. Interhospital practice variation was measured using the median odds ratio. Over the study period, 6091 subjects from 45 hospitals were included. After adjusting for measurable covariates, discharge after 1/2016 was associated with increased odds of receiving digoxin (OR 3.9, p < 0.001). No association was seen between date of discharge and furosemide (p = 0.26) or aspirin (p = 0.12). Prior to 1/2016, the likelihood of receiving digoxin was decreasing (OR 0.9 per year, p < 0.001), while after 1/2016 the rate has increased (OR 1.4 per year, p < 0.001). However, there remains significant interhospital variation in the likelihood of receiving digoxin even after adjusting for known confounders (median odds ratio = 3.5, p < 0.0001). Following publication of studies describing an association between digoxin and improved interstage survival, the likelihood of receiving digoxin at discharge increased without similar changes for furosemide or aspirin. Despite concerted efforts to standardize interstage care, interhospital variation in pharmacotherapy in this vulnerable population persists.

Thrombocytopenia associated with transcatheter closure of giant patent ductus arteriosus

INTRODUCTION

Thrombocytopenia occasionally occurs following the closure of some giant patent ductus arteriosus cases. Unfortunately, there is no associated research describing the associated risk factors for thrombocytopenia post-procedure.

METHODS

We reviewed all patients who received occluders with sizes ≥10/12 mm between January 2013 and June 2019. All the data and information on the characteristics of the patients and their follow-up were recorded. Univariate analysis, receiver operating characteristic curves, and linear regression were used to analyse the risk factors for thrombocytopenia and the predictors of hospitalisation stay.

RESULTS

Finally, 32 patients (17.5%) suffered from thrombocytopenia. Univariate analysis revealed the ratio between occluder disc size (mm) and body weight (kg) (1.71 ± 0.51 versus 1.35 ± 0.53) as an independent predictive factor for thrombocytopenia, and the area under the curve of the ratio of occluder size and body weight for predicting thrombocytopenia post-closure was 0.691 (95% confidence interval: 0.589-0.792, p = 0.001). The best cut-off value for the ratio of occluder size and weight was 1.5895, with a sensitivity and specificity of 68.8 and 66.9%, respectively. Each unit of the ratio of occluder size and body weight predicted an average hospitalisation stay of 2.856 days (95% confidence interval: 1.380-4.332). Treatment with medication did not reduce the hospitalisation stay or benefit platelet restoration.

CONCLUSION

Once the ratio of occluder size and body weight is greater than 1.6, thrombocytopenia always exists. Every unit of the ratio of occluder size and body weight represents an additional 3 days of hospitalisation. Treatment does not reduce the duration of hospitalisation.

Resource Utilization in the First 2 Years Following Operative Correction for Tetralogy of Fallot: Study Using Data From the Optum's De-Identified Clinformatics Data Mart Insurance Claims Database

Background

Despite excellent operative survival, correction of tetralogy of Fallot frequently is accompanied by residual lesions that may affect health beyond the incident hospitalization. Measuring resource utilization, specifically cost and length of stay, provides an integrated measure of morbidity not appreciable in traditional outcomes.

Methods and Results

We conducted a retrospective cohort study, using de‐identified commercial insurance claims data, of 269 children who underwent operative correction of tetralogy of Fallot from January 2004 to September 2015 with ≥2 years of continuous follow‐up (1) to describe resource utilization for the incident hospitalization and subsequent 2 years, (2) to determine whether prolonged length of stay (>7 days) in the incident hospitalization was associated with increased subsequent resource utilization, and (3) to explore whether there was regional variation in resource utilization with both direct comparisons and multivariable models adjusting for known covariates. Subjects with prolonged incident hospitalization length of stay demonstrated greater resource utilization (total cost as well as counts of outpatient visits, hospitalizations, and catheterizations) after hospital discharge (P<0.0001 for each), though the number of subsequent operative and transcatheter interventions were not significantly different. Regional differences were observed in the cost of incident hospitalization as well as subsequent hospitalizations, outpatient visits, and the costs associated with each.

Conclusions

This study is the first to report short‐ and medium‐term resource utilization following tetralogy of Fallot operative correction. It also demonstrates that prolonged length of stay in the initial hospitalization is associated with increased subsequent resource utilization. This should motivate research to determine whether these differences are because of modifiable factors.

Variation in the use of pulmonary vasodilators in children and adolescents with pulmonary hypertension: a study using data from the MarketScan® insurance claims database

Despite progress in pharmacotherapy in pediatric pulmonary hypertension, real-world patterns of directed pulmonary hypertension therapy have not been studied in the current era. A retrospective observational study of children (≤18 years) with pulmonary hypertension was performed using data from the MarketScan® Commercial and Medicaid claims databases. Associations between etiology of pulmonary hypertension and pharmaceutical regimen were evaluated, as were the associations between subject social and geographic characteristics (insurance-type, race, and/or census region) and regimen. Annualized costs of single- and multi-class regimens were calculated. In total, 873 subjects were studied, of which 94% received phosphodiesterase-5 inhibitors, 31% endothelin receptor antagonist, 9% prostacyclin analogs, and 7% calcium channel blockers. Monotherapy was used in 72% of subjects. Phosphodiesterase-5 inhibitors monotherapy was the most common regimen (93%). Subjects with idiopathic pulmonary hypertension, congenital heart disease, and unclassified pulmonary hypertension receive more than one agent and were more likely to receive both endothelin receptor antagonist and prostacyclin analogs than other forms of pulmonary hypertension. Compared to recipients of public insurance, subjects with commercial insurance were more likely to receive more intense therapy (p = 0.003), which was confirmed in multivariable analysis (OR: 1.4, p = 0.03). Receipt of commercial insurance was also associated with increased annual costs across all subjects (p < 0.001) and for the most common specific regimens. The majority of children with pulmonary hypertension receive phosphodiesterase monotherapy, followed by phosphodiesterase–endothelin receptor antagonist two drug regimens, and finally the addition of prostacyclin analogs for three-drug therapy. However, even after adjustment for measurable confounders, commercial insurance was associated with higher intensity care and higher costs (even within specific classes of pulmonary vasodilators). The effect of these associations on clinical outcome cannot be discerned from the current data set, but patterns of treatment deserve further attention.