Background
Congenital diaphragmatic hernia (CDH) is a life-threatening defect in the developing diaphragm's integrity [
1], with a reported incidence of less than 3 per 10,000 live births [
2], and is often accompanied by other congenital anomalies. Management of newborn infants with CDH requires a high skill set, with multidisciplinary team involvement, starting from the point of antenatal diagnosis. Despite improved outcomes over the years [
3], morbidity and mortality remain high (20–40%), even in high volume tertiary referral centers [
4,
5]. A quarter of survivors suffer neurodevelopmental impairment involving all domains, and ranges from motor and sensory (hearing, visual) deficits to cognitive, language, and behavioural impairment [
6]. Various clinical and laboratory parameters and prognostic indices in the perinatal period have been studied to help predict outcomes and mortality [
5,
7‐
10]. Standardized management and regionalized care, involving complex ventilatory and hemodynamic management, improve survival outcomes [
11]. Although the need for Extracorporeal membrane oxygenation (ECMO) [
12] in CDH patients has decreased over the years due to improved understanding of physiology and advances in prenatal and neonatal care, CDH still remains in the top three indications for neonatal respiratory ECMO [
13], and mortality in this group of CDH patients remains unchanged [
14,
15].
Patients with CDH have varying degrees of pulmonary hypoplasia and abnormal pulmonary vascular disease, often leading to various degrees of pulmonary hypertension. In CDH patients, persistent pulmonary hypertension of the newborn (PPHN) is associated with adverse outcomes, and therefore its management remains crucial in the care of these infants [
16]. Up to 30–40% of newborns with CDH can have left (LV) or right ventricular (RV) or biventricular dysfunction, and ventricular interdependence may play a role [
17,
18] Association of ventricular dysfunction and ventricular performance is not only a predictor for disease severity [
19], but also for mortality [
20] and need for ECMO [
21].
Advances in our understanding of cardiovascular physiology in CDH patients has allowed for the optimization of hemodynamics and management of pulmonary hypertension (PH) [
22]. Timed functional echocardiography (f-Echo) assessment, with predefined criteria for assessing the degree of pulmonary hypertension and ventricular dysfunction, helps in the effective management of newborns with CDH. This also aids decision-making in the timing of CDH repair and managing acute postoperative clinical decompensation from pulmonary hypertensive crisis [
23].
Non-response to pulmonary arterial vasodilators in CDH patients may be related to abnormal ventricular function, and it is important to improve cardiac function in addition to reducing pulmonary arterial pressures in this situation [
24].
Sidra Medicine is a greenfield children’s hospital in Doha, Qatar. The neonatal intensive care unit (NICU) is a quaternary referral center for national and international patients with medical, surgical, and cardiac conditions. A national CDH-Qatar (CDH-Q) program was established and standard clinical guidelines for the management of CDH were developed based on recent literature and international guidelines. This study was conducted at Sidra Medicine to test the hypothesis that routine serial echocardiography is an important tool in the standardized management of newborns with CDH, and may improve survival outcomes.
Methods
Study Design
This is a retrospective, observational, single center study conducted at Sidra Medicine hospital, from April 2018 to January 2022. A retrospective review of echocardiography images and clinical charts of all eligible CDH patients admitted to the NICU was done using the hospital's electronic medical record system.
Setting
The NICU at Sidra Medicine hospital has facilities for ECMO, and is well supported by a neonatal hemodynamics team of consultant neonatologists, with expertise in functional echocardiograph. The CDH-Qatar (CDH-Q) program was established with a vision to develop a national quaternary referral center for pre-and post-natal referrals of CDH patients in Qatar and further afield. A local CDH registry was created at Sidra Medicine in 2019 on REDCap® (Research Electronic Data Capture) software [
25] for data sharing and reporting to international CDH registries[
26]. The department used an f-Echo protocol, adapted from the CoDiNOS trial [
27] by the CDH EURO Consortium, for serial assessment of myocardial function and PPHN in CDH patients, at set time points, in order to guide cardiorespiratory management, surgical intervention, and follow up care pre- and post-discharge. Members of hemodynamic and ECMO teams closely followed patients to minimize variations in clinical practice and assist in f-Echo based decisions. Following on from the establishment of CDH-Q program and foundation of standardized management practices (Appendix I), we conducted this retrospective review, with the below objectives.
Primary Objectives:
1.
To assess the impact of standardized management, utilizing serial echocardiography, on mortality amongst newborns with CDH.
2.
To identify echocardiography predictors of mortality.
Secondary Objectives:
1.
To study the correlation of echocardiography markers with respiratory severity score (RSS) and inotropic scores in predicting disease severity and mortality.
2.
To evaluate trends in f-echo and cardiorespiratory parameters used in decision-making for timing of surgical correction.
3.
To study the use of inotropes and milrinone in the treatment of ventricular dysfunction and various pulmonary vasodilators in treatment of acute or chronic pulmonary hypertension related to CDH.
Participants
-
Inclusion Criteria All infants admitted to Sidra NICU with a diagnosis of CDH from April 2018 till January 2022.
-
Exclusion Criteria Infants who received palliative care from birth and those with significant associated congenital cardiac anomalies, other than atrial septal defect (ASD), ventricular septal defect (VSD), and persistent ductus arteriosus (PDA), were excluded from f-Echo analysis but were included in the basic demographic data analysis.
Data Collection
Study data were collected and managed using secure, web-based software-REDCap® electronic data capture tools hosted at Sidra Medicine, Qatar. Patient demographic data included infants’ sex, gestational age, birth weight, prenatal MRI and ultrasound scan results, postnatal treatment, side and size of the defect, age at repair, cardiovascular therapies, ECMO, duration of ventilation, and non-invasive ventilatory support. For size of CDH defect, Congenital Diaphragmatic Hernia Study Group (CDHSG) Staging System was utilized [
28]. In addition, the outcome data on death, discharge, and length of stay was extracted from the CDH registry. Any missing data were collected from the electronic medical records on Cerner Powerchart® (North Kansas City, US) patient management software. Established ECHO protocols in the unit for assessment of myocardial function and PPHN (Appendix IIA), and standardized timings for these assessments were used to collect data (Appendix IIB).
All echocardiograms were performed using the EPIC 7 Philips machine with a S12-4 Hz/ S8-3 multi-frequency sector probe. The first, structural scans, were performed by pediatric cardiology. Functional echocardiography scans were thereafter performed by clinicians from the neonatal hemodynamics team. Researchers collected echocardiography data from the Philips Intellivue® database. Two researchers measured some of the missing f-Echo parameters offline, wherever possible, and cross-verified them to minimize inter-observer variability in reporting.
Timeline for f-Echos
A total of three echocardiograms was studied for each patient at the set time points:
ECHO Parameters
A standard Echo protocol as per published guidelines was followed, and all possible functional Echo parameters were collected as listed in Appendix IIA.
The following measurements were taken:
Persistent Pulmonary Hypertension of the Newborn (PPHN)
PPHN was diagnosed by assessment of right ventricular systolic pressure (RVSP) [calculated from tricuspid regurgitant jet velocity, using the Bernoulli equation], the presence of right-to-left or bidirectional shunting at atrial level or ductus arteriosus, septal wall flattening or paradoxical motion. PH was defined as moderate if RVSP ≥ 45, with or without bidirectional /right-to-left ductal shunting and severe if RVSP ≥ 70 and bidirectional /right-to-left ductal shunting [
29,
30] Pulmonary vascular resistance (PVR) index was calculated as right ventricular ejection time (RVET)/pulmonary artery time-to-peak velocity (TPV).
Cardiac Function (See Supplementary Material)
1.
Markers of LV function – systolic function is assessed by fractional shortening (FS), ejection fraction (EF) of LV with the biplane Simpson's method, and left ventricular output (LVO). Markers of LV diastolic function are early to late ventricular filling velocities (E/A ratio) and isovolumic relaxation time (IVRT) [
31] The mean of three cardiac cycles was calculated for all hemodynamic parameters and used for further analysis and calculations as per standard protocol [
31] Left ventricular systolic dysfunction was defined by fractional shortening less than 25% or ejection fraction less than 50%.
2.
Right ventricular systolic function was assessed using Tricuspid Annular Plane Systolic Excursion (TAPSE) and Fractional Area Change (FAC).
TAPSE was evaluated by measuring total excursion of tricuspid annulus during ventricular systole on M-mode using apical four-chamber view with cursor aligned in the direction of movement of tricuspid annulus. Three measurements were taken, and an average value at two decimal points was recorded for analysis.
FAC was measured using the 2D recording of RV in a four-chamber view by measuring RV area in systole and diastole.
Cardiorespiratory Parameters
Relevant cardiorespiratory parameters were collected at the time of Echo at corresponding time points.
Respiratory severity score (RSS) was calculated using mean airway pressure (MAP) x fractional inspired oxygen (FiO2), and was considered as a marker of severity of illness [
32]. Subgroup analysis was done comparing newborns with RSS less than 4 versus more than 4 as a severity cut-off used in previously published studies [
32].
Vasoactive Inotropic score (VIS) was calculated using the following formula [
33]:
VIS = (dopamine dose (μg/kg/min) + dobutamine dose (μg/kg/min) + 100 × epinephrine dose (μg/kg/min) + 10 × milrinone dose (μg/kg/min) + 10 000 × vasopressin dose (unit/kg/min) + 100 × norepinephrine dose (μg/kg/min).
Data were also collected for inhaled nitric oxide (iNO) and other pulmonary vasodilators, alprostadil and hydrocortisone.
The following outcome data were recorded from Cerner and REDCap®-death, need for ECMO, duration of ventilation, respiratory support or oxygen, inhaled nitric oxide (iNO), other pulmonary vasodilators, various types of inotropic support, day of CDH surgical repair, and length of hospital stay.
Institutional Review Board (IRB) approval for this project was obtained from Sidra Medicine (IRB No-1696088-4). STROBE criteria were followed for reporting this observational study (see Supplementary Material).
Statistical Analysis
Descriptive statistics were used to describe the study population, including gender, age (in days), gestation at birth, birth weight, and singleton/multiple births. Categorical and continuous variables were represented by frequencies, mean ± SD or median (Inter quartile range). To compare continuous variables between groups, the Mann–Whitney U-test was used. For calculating the p-values of association between categorical variables, the Chi-square or Fisher's Exact test was used as appropriate. Freeman's coefficient of differentiation was used as a measure of association between defect size and mortality where 0 represents no association and 1 represents perfect association. Serial TAPSE measurements were analyzed using the rstatix package and a one-way repeated measures ANOVA, which is an extension of the paired-samples t-test for comparing the means of three or more levels of the within-subjects variable. To build ROC curves, the pROC package was used. The Youden Index was used to determine the appropriate cut-off point for the parameters of interest. Survival Analysis was performed using the Kaplan–Meier Model. All statistical analyses were performed using the statistical software R version 4.1.1. Any association with a p-value less than 0.05 was considered significant.
Discussion
This is the first study from Middle Eastern population describing echocardiographic findings in CDH patients. Our calculated estimated prevalence of CDH is 3.82 per 10,000 births, based on average annual births (~ 28,000) in Qatar, [
35] as compared to other reported studies quoting prevalence of around ~ 3 per 10,000 births [
36]. A total of 42 cases of CDH were admitted to our center over a period of 3.5 years, making it a high-volume center as per international guidelines [
37]. The incidence of genetic anomalies in our cohort and in general, in the Middle Eastern populations seems higher, likely due to consanguinity and lower rates of pregnancy termination [
38‐
40]. Although the role of genetics in the pathogenesis of CDH has been well established, only a handful of disease genes have been identified so far. A number of damaging de novo gene variants with potentially pleiotropic effects have also been identified [
41].
Our overall mortality is comparable to internationally reported rates (20–40%), but after excluding confirmed genetic anomalies, the mortality was even lower, which is comparable to reports from many high-volume centers [
42]. The mortality in preterm infants was double of that seen in term infants, consistent with previous studies reporting similar lower survival rates in preterm infants with CDH [
43]. Post-surgical and post-ECMO mortality was also comparable to the CDHSG mortality rate of 14% after surgery [
44] and was influenced by several factors, including the timing of surgery and pre-op stability [
45,
46]. Need for ECMO in our cohort was significantly low (only 2 patients required ECMO, of which 1 survived) compared to published reports of up to 30% [
47,
48]. Echocardiographic assessment was seen to be a vital part of the management approach in these infants, with regards to many of the decisions around inotropes, pulmonary vasodilators, the timing of surgery, and ECMO. We believe that a standardized management [
46] approach and the presence of a dedicated hemodynamic team, along with diligent ventilatory support may have contributed to improved survival outcomes, including the avoidance of need for ECMO in several patients.
Pulmonary hypertension is a known predictor of mortality in CDH patients [
16]. In our cohort, as many as seventy percent of newborns that died and had early echocardiograms, suggesting moderate to severe PH in the first 72 h. In our cohort
, RVSP of more than 45.5 in the first 72 h was found to be a good predictor of mortality. Similar cut-off values are reported by Derya et al.[
29]. In other reports, the mortality rate was found to be nearly 100% in patients with supra-systemic or systemic pulmonary arterial pressure during the first three weeks of life, but the survival rate in infants with pulmonary arterial pressure below half of the systemic pressure was found to be 100%. The risk of mortality in infants with moderate pulmonary hypertension was 75% [
49].
Birth weight less than 2.8 kg was a significant predictor of mortality in our cohort. Previous studies have similarly reported birth weight cut-offs of 2.755 kg as a predictor for mortality [
50]. Higher Post-operative VIS and RSS scores were predictive of mortality in our cohort. This is consistent with previous studies reporting on the use of RSS as a predictor of mortality [
32] and higher post-op VIS scores being predictive of negative outcomes in infants with CDH [
51]. VIS more than 23 was associated with high mortality in our cohort. In patients undergoing cardiac surgery, maximum post-op VIS ≥ 20 predicts an increased likelihood of a poor composite clinical outcome [
52]. Our patients in the high VIS group had more severe pulmonary hypertension and cardiac dysfunction. Those with higher RSS had higher pulmonary pressures and higher use of inotropes. This would be consistent with disease severity.
The improved trends pre-operatively for RSS, TAPSE, and RVSP indicate that clinicians endeavored to achieve cardiovascular stability in patients prior to surgery with regards to need for respiratory support, right ventricular systolic function, and pulmonary pressures. Pre-operative high RSS, pulmonary pressures and poor right ventricular function are important factors associated with mortality and morbidity in patients with CDH, and therefore the stability of these parameters is commonly practiced [
32,
53,
54]. RSS and pulmonary pressures in the immediate preoperative period were also assessed to be potential predictors but did not achieve statistical significance, likely due to our small numbers. However, generally, surgery was timed after achieving respiratory stability and manageable pulmonary hypertension which resulted in stable post-operative period [
50].
Use of Milrinone in our cohort (62%) is higher than in international reports. Milrinone, a phosphodiesterase-III inhibitor with lusitropic and vasodilator effects, was used in up to 30% of CDH infants across the USA. No randomized trials have tested the efficacy or safety of milrinone in CDH neonates, but retrospective studies demonstrated that its use was associated with neither improved OI, PAP, or left ventricular measurements nor adverse events [
55]. The use of iNO in our cohort (59%) is comparable to that reported by the Congenital Diaphragmatic Hernia Study Group registry, where the mean percentage of patients treated with iNO by center was 62.3% (range, 0%-100%) [
44,
56]. Multiple studies have failed to demonstrate a clear benefit of iNO in CDH infants, but its use is still widespread, and it is considered an essential treatment method in the transitional period of CDH patients [
57]. We also had 38% of our patients on sildenafil. Despite the liberal use of these medications in our cohort, our mortality data are comparable or better than some international reports. It is possible that serial and timed functional echocardiography encouraged the timely use of milrinone, pulmonary vasodilators, and appropriate inotropes, which could have played a role in improving our outcomes.
Strengths: Standardised echo schedule and timelines as per protocol were used. The hemodynamic team consists of a group of experienced clinicians. Standardization of technique was emphasized amongst the group by regular hemodynamic meetings and case discussions.
Weaknesses: This is an observational study where stored data were analyzed. Missing images or information could therefore not be obtained retrospectively. Some variation in acquired images and measurements may be present as echocardiograms were performed by several experienced members of the team. In the sicker patients, clinicians prioritized the assessment of only certain important echo parameters, in the interest of maintaining patient stability. Patients with any cardiac anomalies were mainly scanned by cardiologists and therefore did not always have complete functional echocardiography measurements performed at the set time points.
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