Genetic Study of Congenital Heart Defects In
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8585 JMed Genet 1994;31:858-863 Genetic study of congenital heart defects in Northern Ireland (19741978) J Med Genet: first published as 10.1136/jmg.31.11.858 on 1 November 1994. Downloaded from E Jennifer Hanna, Norman C Nevin, John Nelson Abstract echocardiography, have been able to diagnose Congenital heart defects are a major con- lesions more accurately by non-invasive means. genital abnormality and are assuming The aim of this study, which allowed a follow increasing importance. A study was up period of 6 to 10 years (1979-1984), was to undertaken to estimate the incidence of obtain an accurate estimate of the incidence of congenital heart defects in Northern CHD in Northern Ireland. It included the total Ireland over a five year period (1974-1978), live- and stillbirth population over a five year to determine the age at diagnosis and to period (1974-1978) but unfortunately echocar- assess the risk of recurrence in sibs. An diography was not available for all patients incidence rate of 7-3 per 1000 total births during the period of study. was found. This reduced to 3-1 per 1000 Previous studies346"' 1-14 have shown a recur- total births if only invasive methods of rence risk in sibs varying from 1 4% to 3 4%. diagnosis (catheter studies, surgery, or To ascertain the recurrence risk in Northern necropsy) were considered. The overall Ireland, selected families identified by the risk of recurrence for sibs (excluding in- incidence study were examined in greater de- dex patients with chromosomal abnor- tail. In addition it was decided to look at the age malities and syndromes) was 3-1%. In ad- at diagnosis of the congenital heart defect to see dition, excluding families with an affected what proportion escaped detection in the first parent and child gave a recurrence risk of year of life. 2-6%. Many studies'6 15-21) have shown that the pre- By 6 weeks of age 63% of index patients valence of extracardiac abnormalities (ECA) in had been diagnosed and this figure had patients with congenital heart defects is much risen to 88% by 1 year. This has important higher than in the general population, varying implications for studies which include from 9% to 30%. In addition, several investig- only congenital heart defects diagnosed in ators have examined the prevalence of ECA the first year of life. associated with specific congenital heart defects. Of 388 patients with a congenital heart Campbell'6 found the prevalence varied from defect confirmed by invasive criteria, 5% in index patients with atrial septal defect 96 (24-7%) were found to have an extra- (ASD) to 13% in patients with coarctation of cardiac abnormality (ECA). Excluding the aorta (CoA) and pulmonary valve stenosis http://jmg.bmj.com/ those with epilepsy or mental handicap as (PVS). Lamy et al'7 reported a prevalence of the sole ECA left 91 (23-5%) with an ECA. 7.4% associated with CoA rising to 26 8% with This highlights the importance of looking ASD. Boon and Roberts2' found a prevalence of for other abnormalities in a child with a 7% in 100 cases of CoA whereas Boon et al22 congenital heart defect. found a 16% prevalence of ECA in 100 cases of The 388 index patients had 952 sibs of tetralogy of Fallot (TF). Williamson23 found a whom 72 (7-6%) had an ECA. Excluding prevalence of 8-2% of ECA in 135 cases of ASD those with minor abnormalities (inguinal secundum. on October 1, 2021 by guest. Protected copyright. hernias, undescended testes) as the sole Some studies included only "major" abnor- ECA left 62 (6-5%) with a major ECA. In malities, while others included "minor" ab- addition, excluding those with epilepsy or normalities, for example, inguinal hernia, mental handicap as the sole ECA left 51 undescended testis. Some were restricted to (5 4%) with a major ECA. Since parents congenital malformations while others also in- are often reassured after the birth of a cluded epilepsy and mental handicap. Overall, child with a congenital heart defect that it appeared that the majority of ECA were their risk of having a child with a non- or Department of related to the musculoskeletal, genitourinary, Medical Genetics, cardiac abnormality is no greater than gastrointestinal systems. We were interested to Royal Victoria the general population this finding has ascertain if similar associations were found in Hospital, important implications for genetic coun- Grosvenor Road, our population. Belfast, selling. Northern Ireland Subjects and methods E J Hanna (J Med Genet 1994;31:858-863) N C Nevin Multiple independent sources of ascertainment J Nelson of infants with congenital heart defects were the Correspondence to available in Northern Ireland during study Dr Nelson, Genetic Services Many studies'-1" have looked at the incidence of period. These included hospital cardiology rec- of Western Australia, King Edward Memorial Hospital, congenital heart defects (CHD) using different ords, the Registrar General's Congenital Mal- 374 Bagot Road, Perth 6008, methods of ascertainment and differing follow formation Notification, the Child Health Sys- Western Australia. up periods. Some studies6"" have looked at the tem, necropsy records, death certificates, Received 29 September 1993 Revised version accepted for incidence of congenital heart defects in the records of the Department of Medical Genetics, publication 24 May 1994 first year of life and, with the advent of and neonatal paediatric records. Genetic study of congenital heart defects in Northern Ireland (1974-1978) 859 Table I Congenital heart defects: source of ascertainment (total no of patients ascertained= 972) 1974-1978 Cardiologist Medical Registrar Child Necropsy Death Neonatal records genetic General health records certificates records records system J Med Genet: first published as 10.1136/jmg.31.11.858 on 1 November 1994. Downloaded from Total ascertained 545 120 303 146 187 234 261 (56 1%) (12 3%) (31-2%) (15 0%) (19 2%) (24 1%) (26 9%) Solely ascertained 298 12 32 1 25 37 116 (307%) (1 2%) (33%) (0 1%) (26%) (38%) (11 9%) At the time of the study there were two ascertained. Table 1 shows the distribution by cardiologists in the province who dealt with the source of ascertainment. The number of infants majority of paediatric referrals including all with congenital heart defects and the incidence children who progressed to catheterisation or for each year are shown in table 2. The incid- cardiac surgery. The Registrar General's Con- ence ranged from 6-0 per 1000 total births in genital Malformation Notification is a volun- 1975 to 8 6 per 1000 total births in 1977, with a tary system for the notification of congenital mean for the study period of 7 3 per 1000 total malformations in Northern Ireland and the births. If only those with a diagnosis confirmed Child Health System is a register of all births in by invasive methods (catheterisation, cardiac Northern Ireland.24 Each record, in addition to surgery, necropsy) are considered (417 patients) identification data, also includes information on this gave an incidence rate of 3 15 per 1000 total a maximum of four congenital malformations. births. During the study period (1974-1978) records of necropsies, which were carried out mainly in the Belfast and Londonderry hospitals, were RECURRENCE RISK IN SIBS examined. Copies of all death certificates and Of the 417 index patients who had the diagnosis stillbirth records were examined and details confirmed by catheter studies, surgery, or nec- extracted on all children born between 1974- ropsy, 388 (93%) were traced. Only 29 families 1978 inclusive who died with a congenital heart (7-0%) could not be contacted. Of these 24 defect. The diagnostic index of the Department could not be traced, four had moved from ofMedical Genetics and neonatal records for all Northern Ireland, and the remaining child was births in the three major maternity units in in long term foster care and his natural mother Belfast were also examined. Stillborn or prema- was unavailable. The 388 index patients had a ture babies with a patent ductus arteriosus or total of 952 sibs of whom 28 (2 9%) had a babies whose ductus closed spontaneously congenital heart defect. There were also 32 half within two weeks of birth were not included in sibs, of whom one (3 1 %) had a congenital heart the study. defect. A chromosomal abnormality was identi- To estimate the recurrence risk in sibs, the fied in 12 of the index patients. When these family history of children with a congenital patients were excluded this left 376 index heart defect was documented. It was decided to patients with a CHD confirmed by catheter investigate only the families of children in studies, surgery, or necropsy who had been http://jmg.bmj.com/ whom the diagnosis had been confirmed by traced. When the sibs of the 12 index patients catheter studies, surgery, or necropsy since with a chromosomal abnormality were echocardiography was not available for all excluded, this left 921 sibs of whom 28 (3 0%) patients during the period of study and was had a congenital heart defect. only becoming established during our follow up Seven of the index patients had syndromes period (1979-1984). which were known to be associated with con- During the period (1974-1978 inclusive), 972 genital heart defects (three with Noonan, one on October 1, 2021 by guest. Protected copyright. children with a congenital heart defect were with Holt-Oram, one with Klippel-Feil, one ascertained. Of these, 417 had the diagnosis with fetal hydantoin, and one with Goldenhar confirmed by invasive criteria (catheter studies, (oculoauriculovertebral) syndrome). When surgery, or necropsy). In this group 388 fam- these patients were excluded this left 369 index ilies (93%) were traced, the parents were in- patients who had 909 sibs of whom 28 (3 1%) terviewed, and a detailed pedigree obtained.25 had a congenital heart defect.