Congenital heart disease refers to structural or functional heart disease that is present at birth.
It represents the most frequently occurring congenital anomaly in newborns.Reference Dastgiri, Stone, Le-Ha and Gilmour 1 – Reference Hoffman and Kaplan 6 In all, 28% of all major congenital anomalies consist of heart defects.Reference Dolk, Loane and Garne 3 The estimate of eight per 1000 live births is generally accepted as the best approximation,Reference Dolk, Loane and Garne 3 – Reference Moons, Sluysmans and De Wolf 5 although large variations in the data occur across studies.Reference Hoffman and Kaplan 6 The causes of most congenital heart anomalies are unknown, but thought to be multi-factorial and resulting from a combination of genetic predisposition and environmental stimuli. Advances in cardiovascular diagnostics and cardiothoracic surgery over the past century have led to increased survival of newborns with congenital heart disease, 7 and a dramatic increase in the population of school-aged and adult survivors of infant heart surgery. This has been accompanied by increased recognition of the long-term morbidities associated with congenital heart disease and has created a steadily growing population of patients with grown-up congenital heart disease. The prevalence of congenital heart disease in adults has been estimated to be four per 1000.Reference Khairy, Ionescu-Ittu, Mackie, Abrahamowicz, Pilote and Marelli 8 The aim of the present study was to describe the birth prevalence and treatments applied to Palestinian children with congenital heart disease who were born in the Gaza Strip in 2010, and to provide a cohort for long-term follow-up.
Methods
Study population
The occupied Palestinian territory consists of two distinct areas: the West Bank, including East Jerusalem and the Gaza Strip. The Gaza Strip is about 41 km (25 miles) long, and between 6 and 12 km (4–7.5 miles) wide, with a total area of 360 sq km (140 square miles). It is home to a population of about 1.7 million people, most of them refugees or descendants of refugees. There are four clinics for paediatric cardiology in the Gaza Strip, one of them based at a tertiary care centre. The health-care system allows easy access to the paediatric cardiology clinics, and thus nearly all children with congenital heart disease in Gaza have been evaluated by the paediatric cardiology programmes at these four clinics. All patients registered in the databases of these programmes and born in Gaza in 2010 were eligible for inclusion in the present study. We only included cases proven by echocardiography in live births. We followed up these children for 18 months.
Measurements and definitions
Data obtained from the medical records included date of birth, postal code, gender, cardiac diagnoses, date and type of interventions, and date and cause of death. To determine whether a patient should be included in this study, we applied Mitchell'sReference Mitchell, Korones and Berendes 9 definition of congenital heart disease to the cases under review: gross structural abnormalities of the heart or intrathoracic great vessels that are actually or potentially of functional significance. Patients with the following anomalies were excluded: isolated patent foramen ovale; rhythm disturbances without structural defects; isolated mild peripheral pulmonary stenosis; isolated innocent patent ductus arteriosus; patent ductus arteriosus in pre-term infants; hereditary disorders without cardiac consequences; and malpositioning of the heart without structural defects.
Congenital heart disease is often characterised by a combination of different heart lesions. To categorise patients according to their primary heart defect, we used a hierarchy of heart defects previously developed by the CONCOR (CONgenitale COR Vitia) project,Reference van der Velde, Vriend, Mannens, Uiterwaal, Brand and Mulder 10 an initiative to form a national registry of patients with congenital heart disease in the Netherlands. Some modifications to the list of heart defects were made: univentricular heart was divided into hypoplastic left heart syndrome and univentricular physiology; truncus arteriosus was added; and Marfan syndrome and pulmonary arterial hypertension were removed from the list.Reference Moons, Sluysmans and De Wolf 5 To calculate the birth prevalence of congenital heart disease and specific heart defects, we obtained the birth rate information in 2010 in the Gaza Strip from the database of the ministry of health.
Data analysis
The study was approved by the Human Research Ethics Committee. The overall incidence of congenital heart disease and the incidence of each type of defect were estimated and the type of surgery or catheterisation documented and tabulated.
Results
In 2010, 59,757 live births were registered in the Gaza Strip. In the four paediatric cardiology clinics, we recorded 598 children with congenital heart anomalies who were born alive in 2010. This yielded a birth prevalence of congenital heart disease of 10 per 1000 births (Table 1). The most prevalent heart defects in this sample were ventricular septal defects (28%); atrial septal defects type II (17%); patent ductus arteriosus (8.5%), and pulmonary valve abnormalities (8%) (Table 2). The gender distribution in the overall sample was 335 (56%) girls and 265 (44%) boys (Table 1). In all, 150 children (25%) had a cardiosurgical operation and 48 (8%) a catheter intervention. A total of 42 children (7%) died. Most of them died during the first 6 months of life. The actuarial survival of children with congenital heart disease 6 months and 1 year after birth was 94% and 93%, respectively. The reasons for death were no surgical intervention (n = 20); cardiac failure (n = 6); extracardiac reasons or multi-organ failure (n = 5); post-operative complications (n = 4); operative complications (n = 3); sudden death (n = 1); and pulmonary complications (n = 3) (Table 3).
Table 1 Total birth, gender and birth prevalence of congenital heart disease among infants born alive in the Gaza Strip in 2010.
Table 2 Birth prevalence of each congenital heart anomaly.
AoS = Aortic Stenosis; ASD = atrial septal defect; AVSD = atrioventricular septal defect; COA = coarctation of aorta; DCM = dilated cardiomyopathy; DORV = double outlet right ventricle; HLHS = Hypoplastic left heart syndrome; PA = pulmonary atresia; PDA = patent ductus arteriosus; PS = pulmonary stenosis; Single V = Single Ventrical; Shone C = Shone Complex; TA = Tricuspid atresia; TAPV = total anomalous pulmonary venous return; TGA = transposition of the great arteries; TOF = tetralogy of Fallot; VSD = ventricular septal defect.
Table 3 Causes of death.
Discussion
To the best of our knowledge, this is the first population-based investigation of the birth prevalence and treatment of children with congenital heart disease in the occupied Palestinian territory. Its merit is that it includes the entire Gazan population of children with congenital heart disease. Another advantage of this population-based study is that it has identified a cohort for longitudinal follow-up studies to investigate the progress and outcomes of patient management. Our estimate of the birth prevalence of congenital heart anomalies of 10 per 1000 live births is higher than most estimates in Western Europe and in North America (8.2 and 6.9 per 1000 live births, respectively),Reference Bernier, Stefanescu, Samoukovic and Tchervenkov 4 , Reference Moons, Sluysmans and De Wolf 5 , Reference van der Linde, Konings and Slager 11 but close to Asian figures (9.3 per 1000 live births) (Table 4). Owing to the fact that babies who die perinatally in the Gaza Strip are not examined at autopsy, we may have underestimated the true number of serious heart defects. Indeed, as about 8% of heart defects are diagnosed after the age of 5 years,Reference Wren and O'Sullivan 12 the true estimate may be even higher.
Table 4 Birth prevalence of congenital heart anomalies.
The birth prevalence of individual heart defects found in our study is not entirely consistent with that of previous reports. Similar to other studies, ventricular septal defects, atrial septal defects, and pulmonary valve abnormalities have been the most frequently occurring heart defects,Reference Moons, Sluysmans and De Wolf 5 , Reference Bosi, Garani, Scorrano and Calzolari 13 – Reference Samanek and Voriskova 21 but surprisingly a higher prevalence of major heart defects – hypoplastic left heart syndrome, 2 versus 1 per 10,000; pulmonary atresia, 2.5 versus 1 per 10,000; tricuspid atresia, 3 versus 0.5 per 10,000; and total anomalous pulmonary venous return, 2 versus 1 per 10,000 – were observed compared with the literature.Reference Moons, Sluysmans and De Wolf 5 , Reference van der Linde, Konings and Slager 11 Obviously this calls for further genetic and environmental investigation. Ventricular septal defect was the most encountered heart defect in our study, accounting for 28% of the cases. The high prevalence of ventricular septal defect in our study and in other reports might be due to the fact that most children who present to paediatric cardiology units are still in the neonatal phase and do so because they show clinical signs and symptoms, for example heart murmur. The highest reported prevalence of ventricular septal defect in neonates,Reference Roguin, Du, Barak, Nasser, Hershkowitz and Milgram 22 of which close spontaneously between 1 and 10 months of life, can therefore be responsible for the high number of children with ventricular septal defect.Reference Hoffman, Kaplan and Liberthson 16 In all, 14% of our patients with ventricular septal defects were operated on to close the defect, which is relatively higher than in other reported studies.Reference Moons, Sluysmans and De Wolf 5
The low prevalence of left ventricular outflow tract obstructions – coarctation and aortic stenosis – contrasts sharply with European figures.Reference van der Linde, Konings and Slager 11 The same was observed in Japan, another Asian country, where aortic stenosis and coarctation of the aorta were reported in only 3.7% of all patients with congenital heart disease. Studies of ethnic influence on the pattern of congenital heart disease in the United Kingdom revealed a higher frequency of coarctation of the aorta in non-Asian (9%) compared with Asian (3%) infants. This might be related to racial and genetic factors.
All cases of hypoplastic left heart syndrome were born between June and September, which seems to be very strange and unexplained and needs further confirmation of continuous registration.
Overall, 33% of our sample received an intervention during the course of the 18-month follow-up period. Catheter interventions were performed in 8% of the children in our series. The proportion of patients that underwent a cardiosurgical operation is in keeping with previous reports of patients with univentricular physiology; tetralogy of Fallot; transposition of the great arteries; atrioventricular septal defect; pulmonary valve abnormalities; and ventricular septal defects. The survival of newborns with congenital heart disease continues to improve. Although the overall life expectancy of these newborns is high, vulnerable subgroups do exist. Univentricular physiology, pulmonary atresia with ventricular septal defect, tetralogy of Fallot, and left ventricular outflow tract obstruction was associated with significantly higher mortality than other heart defects. All our patients with hypoplastic left heart syndrome left and expired without surgery.
Study limitations
The children were referred to paediatric cardiology when a clinical problem was detected. In the Gaza Strip, deliveries mainly occur in hospitals and a routine assessment of every newborn by a pediatrician within the first 7 days of life is common practice. Thus, heart murmurs are easily detected. However, systematic echocardiographical screening of the entire population is not done, and thus subclinical heart defects, such as subclinical ventricular septal defects, mild pulmonary stenosis, or small atrial septal defect, have been missed. Furthermore, we excluded isolated peripheral pulmonary stenosis, as well as patent ductus arteriosus and patent foramen ovale, which would not require closure. This may have affected the birth prevalence calculation in the present study. The higher birth prevalence of congenital heart disease compared with published estimates from elsewhere may be attributable to one or more of several factors, including low socio-economic status, multigravidity, the environment, genetic and ethnic factors, and high consanguinity rates, but we do not have data to explore these possibilities.
Conclusion
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• This population-based study conducted in the Gaza Strip yielded a birth prevalence of congenital heart disease of 10 per 1000 live births.
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• The birth prevalence of congenital heart disease and the prevalence of specific heart defects are not consistent with estimates from elsewhere.
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• What is surprising to us is the higher prevalence of major heart defects, compared with other reported studies and the literature, such as hypoplastic left heart syndrome, pulmonary atresia, tricuspid atresia, total anomalous pulmonary venous return. This should be compared with other surrounding countries in order to find possible genetic or social explanations.
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• Survival is nevertheless good, suggesting an ongoing improvement of life expectancy. Hence, the prevalence of congenital heart disease in the community will probably continue to increase.
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• The findings of this study are not only relevant for clinicians and hospital administrators, but are also relevant for public health. Furthermore, this study can serve as a basis for the longitudinal follow-up of this cohort of patients, with the long-term aim of exploring the progress and outcomes of patient management.
Acknowledgment
The authors would like to thank Sir Iain Chalmers one of the founders of the Cochrane Collaboration, and coordinator of the James Lind Initiative for his academic support.
Financial Support
This research received no specific grant from any funding agency, commercial or not-for-profit sectors.
Conflicts of Interest
None.
