Pulmonary hypertension is associated with diverse cardiac, pulmonary, and systemic diseases in neonates, infants, and older children and contributes to significant morbidity and mortality. However, current approaches to caring for pediatric patients with pulmonary hypertension have been limited by the lack of consensus guidelines from experts in the field. In a joint effort from the American Heart Association and American Thoracic Society, a panel of experienced clinicians and clinician-scientists was assembled to review the current literature and to make recommendations on the diagnosis, evaluation, and treatment of pediatric pulmonary hypertension. This publication presents the results of extensive literature reviews, discussions, and formal scoring of recommendations for the care of children with pulmonary hypertension.

Pediatric Pulmonary Hypertension: Guidelines From the American Heart Association and American Thoracic Society

Pediatric Pulmonary Hypertension

Abnormalities of the pulmonary circulation, including the development of pulmonary hypertension (PH), complicate the course of chronic lung disease (CLD) in newborns and contribute to late morbidity and death during infancy, especially in the settings of bronchopulmonary dysplasia (BPD), congenital diaphragmatic hernia (CDH), and pulmonary hypoplasia.1–4 Diagnosis of pulmonary vascular disease in this population is difficult and requires a high degree of suspicion because the symptoms of PH may be subtle, even in patients with significantly elevated pulmonary artery (PA) pressures. In addition, clinical signs of PH may be masked by or attributed to signs of CLD itself, further delaying recognition of PH. Detection of pulmonary vascular abnormalities is important because it can provide prognostic information and may dictate the need for such therapies as vasodilator treatment, more-aggressive respiratory support, and surgical or interventional cardiac catheterization procedures. Assessment of the magnitude of PH influences decisions regarding medical management and pursuit of additional diagnostic and therapeutic procedures.

Doppler echocardiography is a noninvasive test that is commonly used to screen for PH and to help guide management. Cardiac catheterization, the standard method for assessing pulmonary vascular disease, is a much more invasive test and has been reserved for patients for whom noninvasive assessments are considered inadequate and for assessment of acute vasoreactivity, to guide long-term therapy. Previous studies in adults and children evaluated the ability of echocardiography to diagnose and to determine the severity of PH,5–12 but few studies in infants compared directly the echocardiographic estimates of systolic PA pressure (sPAP) derived from the tricuspid regurgitant jet velocity (TRJV) with direct measurements obtained through cardiac catheterization,7,12 and no study concentrated on infants and young children with CLD.

In addition, most of the previous studies assessed the validity of echocardiographic measurements performed simultaneously with cardiac catheterization measurements, showing good correlation between sPAP estimated with echocardiography and the value measured with cardiac catheterization.5–7,9–12 Although performing simultaneous echocardiographic measurements during cardiac catheterization is the best study design to evaluate the validity and capability of echocardiographic measurements, this approach does not mirror the use of echocardiography in clinical practice, where echocardiographic interpretation serves as the basis for the decision to refer patients for cardiac catheterization (often performed days to weeks later) and guides therapy. Questions remain regarding whether echocardiography identifies correctly patients who should undergo cardiac catheterization and whether it provides sufficient information for effective monitoring of patients with established PH without cardiac catheterization, especially children with CLD.

In our institution, cardiac catheterization is reserved for patients with CLD who have persistent signs of severe cardiorespiratory disease and are suspected of having significant PH after optimal management of their CLD and associated morbidities, to assess the severity of PH; to exclude or to document the severity of associated anatomic cardiac lesions; to define the presence of systemic/pulmonary collateral vessels, pulmonary venous obstruction, or left heart dysfunction; and to assess pulmonary vascular reactivity in patients who fail to respond to oxygen therapy alone. In addition, patients being treated for PH with vasodilator therapy are referred for cardiac catheterization when clinical improvement is in doubt or echocardiographic measurements fail to provide adequate hemodynamic assessment.

In the present study, we sought to determine the effectiveness of echocardiography, as used in clinical practice, to predict the presence and severity of PH in a population of children <2 years of age with CLD attributable to BPD, CDH, or pulmonary hypoplasia who sub-sequently underwent cardiac catheterization. Our objectives were to determine how often the sPAP can be estimated with echocardiography by using the TRJV, whether the sPAP estimated with echocardiography predicts accurately PH severity, as measured during subsequent cardiac catheterization, whether other qualitative echocardiographic signs of PH predict the presence of PH in the absence of a measurable TRJV, and ultimately whether echocardiographic results are of sufficient reliability to diagnose and to manage PH without cardiac catheterization.

/pdf/clinical-utility-of-echocardiography-for-the-diagnosis-and-52i58eqe5y.pdf

Clinical utility of echocardiography for the diagnosis and management of pulmonary vascular disease in young children with chronic lung disease.

Pulmonary hypertension (PH) is increasingly recognized as a complication of bronchopulmonary dysplasia (BPD) and is associated with increased morbidity, mortality, and healthcare expenditure. Despite many recent clinical advances, pulmonary vascular disease (PVD) remains an important contributor to poor outcomes in BPD. Understanding the relationship between BPD and PH and identifying optimal therapies may help minimize morbidity and improve outcomes.

Pulmonary hypertension in bronchopulmonary dysplasia

Pulmonary hypertension contributes to morbidity and mortality in both the term newborn infant, referred to as persistent pulmonary hypertension of the newborn (PPHN), and the premature infant, in the setting of abnormal pulmonary vasculature development and arrested growth. In the term infant, PPHN is characterized by the failure of the physiological postnatal decrease in pulmonary vascular resistance that results in impaired oxygenation, right ventricular failure, and pulmonary-to-systemic shunting. The pulmonary vasculature is either maladapted, maldeveloped, or underdeveloped. In the premature infant, the mechanisms are similar in that the early onset pulmonary hypertension (PH) is due to pulmonary vascular immaturity and its underdevelopment, while late onset PH is due to the maladaptation of the pulmonary circulation that is seen with severe bronchopulmonary dysplasia. This may lead to cor-pulmonale if left undiagnosed and untreated. Neonatologist performed echocardiography (NPE) should be considered in any preterm or term neonate that presents with risk factors suggesting PPHN. In this review, we discuss the risk factors for PPHN in term and preterm infants, the etiologies, and the pathophysiological mechanisms as they relate to growth and development of the pulmonary vasculature. We explore the applications of NPE techniques that aid in the correct diagnostic and pathophysiological assessment of the most common neonatal etiologies of PPHN and provide guidelines for using these techniques to optimize the management of the neonate with PPHN.

/pdf/application-of-neonatologist-performed-echocardiography-in-1o4oj59ldj.pdf

Application of Neonatologist Performed Echocardiography in the assessment and management of persistent pulmonary hypertension of the newborn.

Doppler and direct measurements of right ventricle to right atrial pressure drop were made during cardiac catheterisation on 28 occasions in 26 infants with congenital heart disease. Age was 10 days to 12 months (median 4.5 months), and weight was 3.1 to 9.0 kg (median 4.7 kg). We measured peak velocity of tricuspid regurgitation by continuous wave Doppler, and the pressure drop was calculated using the modified Bernoulli equation (delta p = 4v2). There was a high correlation (r = 0.95) between direct and Doppler measurements. Doppler values tended to underestimate the right ventricle to right atrial pressure drop, but this was not of clinical significance (mean 2 mm Hg). The 95% confidence interval for the Doppler velocity was -0.41 to +0.26 m/sec, and was consistent across the range of pressures studied. Variability between observers was tested, by two observers performing sequential paired examinations on 16 newborn babies with tricuspid regurgitation. The coefficient of repeatability was 6.3 mm Hg (95% confidence interval 4.7 to 9.5 mm Hg) or 0.26 m/sec (0.18 to 0.50 m/sec). This method of right ventricular pressure estimation, validated previously only in older children and adults, is a reproducible and accurate technique in infants with tricuspid regurgitation.

https://adc.bmj.com/content/archdischild/69/2/216.full.pdf

Right heart pressure determination by Doppler in infants with tricuspid regurgitation.

Despite the increasing use of Doppler echocardiographic (DE) techniques to determine pulmonary arterial pressure in the neonate undergoing intensive care, there have been no studies comparing their repeatability in this population. Our objective was to compare the repeatability of four such techniques in neonates. The study was conducted in two regional neonatal units serving the North East of England. Group A (repeatability between observers): Two experienced observers performed detailed DE examinations, one directly after the other. Group B (within observer repeatability/temporal variability): One observer performed two examinations 1 hour apart. Group A comprised 15 preterm babies (26–36 weeks' gestation, 975–2915 g), most with mild respiratory failure; 4 healthy term babies; and 7 with congenital heart disease, in whom tricuspid regurgitation (TR) only was measured. Their ages were 18 hours to 12 days. Group B comprised 11 babies aged 12–64 hours with moderate to severe respiratory failure; 10 were preterm (26–36 weeks, 785–2800 g). We recorded four measurements: (1) Peak velocity of TR in m/s; (2) peak left-to-right ductal flow velocity (PDAmax in m/s); (3) TPV/RVET ratio; and (4) PEP/RVET ratio, where TPV = time to peak velocity at the pulmonary valve, PEP = right ventricular preejection period, and RVET = right ventricular ejection time. The Bland-Altman analysis was used to produce the coefficient of repeatability (CR: 95% confidence limits of repeatability), also expressed as a repeatability index (CR/mean value) and as a number of ``confidence steps''—a measure of sensitivity of the technique to hemodynamic change (range of values within the population/CR). Between-observer and within-observer repeatabilities were similar. Within-observer CR and index (%) results were for TR ± 0.26 m/s (9%); for PDAmax, ± 0.48 m/s (39%); TPV/RVET 0.1:1.0 (34%), PEP/RVET 0.12:1.00 (36%). TR and PDAmax had the largest number of confidence steps in the expected range of values (TR 8.5; PDA max 6.5; TPV/RVET 3.2; PEP/RVET 3.2). The most repeatable technique was TR, but PDAmax would also be useful for a serial study owing to the potential for large change. Systolic time interval ratios were less repeatable and likely to be less sensitive indicators of hemodynamic change.

Estimation of Pulmonary Arterial Pressure in the Newborn: Study of the Repeatability of Four Doppler Echocardiographic Techniques

Right ventricular dilatation is an infrequent finding at fetal echocardiography. Previous studies have documented an association with aortic coarctation. However, there are associations with other congenital abnormalities. We reviewed our experience of fetal right heart dilatation in order to recognize concurrent anomalies and to assess the outcome of the affected fetuses. We studied all fetuses with right ventricular dilatation over a 5-year period. We documented associated cardiac and noncardiac lesions, and outcome data were assessed in terms of the number of fetuses that were born live and the number surviving to 2 months of age. Forty-three fetuses with right heart dilatation were seen. Fifteen had associated cardiac abnormalities: most commonly coarctation (n = 4) and VSD (n = 4). Seven had associated noncardiac abnormalities. There were seven fetuses who also had chromosomal abnormalities. In total, there were three terminations of pregnancy, four intrauterine deaths, one stillbirth and 35 live-births. Twenty-eight were alive at 2 months of age (70% of the nonterminated pregnancies). Fetal right heart dilatation is frequently associated with both cardiac and noncardiac congenital abnormalities. Our outcome figures suggest a guarded prognosis be given during counseling of parents of fetuses with right heart dilatation.

Right ventricular dilatation in the fetus: a study of associated features and outcome.

The haemodynamic responses to isometric exercise of eight recipients of orthotopic heart transplants and eight healthy controls were studied. Each performed sustained exercise at 30% of maximal voluntary contraction for three minutes on a handgrip dynamometer. Cardiac output was measured by combined Doppler and cross sectional echocardiography before exercise and every 30 seconds during and after exercise. In the controls cardiac output and blood pressure increased significantly owing to an increase in heart rate with no change in stroke volume. In the transplant group cardiac output, heart rate, and stroke volume remained unchanged throughout exercise. In contrast with its response to dynamic exercise the denervated human heart is unable to increase cardiac output during isometric exercise. The pressor response that occurs is mediated via an increase in peripheral vascular resistance.

/pdf/isometric-exercise-in-the-denervated-heart-a-doppler-pje0fpxn6u.pdf

Isometric exercise in the denervated heart: a Doppler echocardiographic study.

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Papers

Right heart pressure determination by Doppler in infants with tricuspid regurgitation.

Estimation of Pulmonary Arterial Pressure in the Newborn: Study of the Repeatability of Four Doppler Echocardiographic Techniques

Right ventricular dilatation in the fetus: a study of associated features and outcome.

Isometric exercise in the denervated heart: a Doppler echocardiographic study.