THE MODE OF INHERITANCE IN ISOLATED LAEVOCARDIA AND DEXTROCARDIA AND SITUS INVERSUS

Malformations Extracardiaques Associées à des Cardiopathies Congénitales (Etude statistique portant sur 1000 cas)

The authors have studied the frequency and nature of associated malformations in a series of 1000 patients with congenital heart disease. Etiological factors have been statistically analyzed, too.

Heterotaxy: associated conditions and hospital-based prevalence in newborns

PURPOSE

To provide insight into the possible etiology and prevalence of heterotaxy, we studied conditions associated with heterotaxy in a consecutive hospital population of newborns.

METHODS

From 1972 to March, 1999 (except February 16, 1972 to December 31, 1978), 58 cases of heterotaxy were ascertained from a cohort of 201,084 births in the ongoing Active Malformation Surveillance Program at the Brigham and Women's Hospital. This registry includes livebirths, stillbirths, and elective abortions. Prevalence among nontransfers (i.e., patients whose mothers had planned delivery at this hospital) was calculated as approximately 1 per 10,000 total births (20 of 201,084).

RESULTS

We analyzed a total of 58 patients consisting of 20 (34%) nontransfers and 38 (66%) transfers. Patients were categorized by spleen status as having asplenia (7 nontransfers, 25 total), polysplenia (8, 20), right spleen (4, 11), normal left (0, 1), and unknown (1, 0). Among the 20 nontransfer and 59 total heterotaxy patients, the following associated medical conditions were present: chromosome abnormality (1 nontransfer, 2 total), suspected Mendelian or chromosome microdeletion disorder (1 nontransfer, 6 total), and maternal insulin-dependent diabetes mellitus (1 nontransfer, 2 total). There were 6 twins (1 member each from 6 twin pairs including 1 dizygous, 4 monozygous, 1 conjoined; 2 were nontransfers). An associated condition occurred in 5 (25%) nontransfer and 16 (28%) total patients, or among 10 of 53 singleton births (19%).

CONCLUSIONS

Although most cases of heterotaxy in this series were sporadic events, an associated condition was present in about one-fourth of the cases. Not all of these conditions would be considered causative etiologies. Based on this small series alone, maternal insulin-dependent diabetes cannot be viewed as a risk factor for heterotaxy. However, the specific association of diabetes with polysplenia with/without left atrial isomerism is noteworthy, and adds weight to animal and epidemiologic case-control data.

Defects in the determination of left-right asymmetry

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Familial situs inversus and congenital heart defects

The midline is a major determinant in the lateral symmetry of the embryo and represents a developmental field which, if defective, may lead to an abnormal situs determination. A family in which four out of seven children had situs inversus and/or congenital heart defects is presented. This report confirms the autosomal recessive inheritance of this developmental field defect.

A possible increase in the incidence of congenital heart defects among the offspring of affected parents

The incidence of congenital heart disease in the children of 219 probands was determined. Each of these probands had one of four selected defects: atrial septal defect, coarctation of the aorta, aortic valve stenosis or complex dextrocardia. Of their children, 8.8% had substantial congenital cardiac defects. This is a much higher incidence than that reported in most comparable studies. The difference is highly significant statistically and therefore is likely to be genuine. The cause of the high recurrence is probably environmental.

World survey of the common cardiac malformations: developmental error or genetic variant?

The common cardiac malformations are prevalent throughout the world, in countries of high technology and among the primitive races. These same malformations were described 200 years ago, ectopia cordis 5,000 years ago. Their recent increase is directly related to the advent of cardiac treatment. Most cardiac malformations known to man occur in the dog. The prevalence rate of these malformations is the same in the dog and in man (5-8/1,000). Several of the malformations are heritable in specific breeds of dogs, one in rabbits, another in rats. These malformations occur in various animals that cannot interbreed. Hence the deoxyribonucleic acid (DNA) that codes these malformations must lie in that portion of the DNA common to all mammals. This suggests that these malformations occurred during the evolution of the Mammalia. Mammals evolved from reptiles, animals with hearts of various structures for the separation of arterial and venous blood. Although the "normal" heart is the most compatible with mammalian life and hence the most common, some mammals may have evolved with a heart with different structures for the separation of arterial and venous blood. Some of these hearts have persisted. These primeval hearts we call cardiac malformations of the cyanotic group. Malformations that apparently are arrests in the development of the normal heart (patent ductus arteriosus, atrioventricular canal) may represent stages in the evolution of the "normal" heart. Although teratogens and mutagens do exist, the author conceives of congenital cardiac malformations not as arrests or errors in the development of a "normal" heart but as genetic variants.

Inheritance of Kartagener syndrome

The surmised autosomal recessive inheritance of situs inversus of Kartagener syndrome is re-examined on the hypothesis that the homozygous state replaces lateralization of the viscera in normal ontogeny by an indifferent lateralization. The segregation ratio in the progeny of two carrier parents (if there were no ascertainment bias) would then be 1/8. The estimated segregation ratio under the assumption of complete (truncate) ascertainment is 0.124. The implications for genetic counseling are discussed.

Renal dysplasia and asplenia in two sibs

A family is reported in which two sibs, one male and the other female, both died within 24 hours of birth with enlarged polycystic kidneys. Postmortem histology in the second child showed gross renal dysplasia. In both children the pancreas was enlarged, nodular and cystic but the liver appeared macroscopically normal. In the second child, histological examination confirmed pancreatic fibrosis with cystic dilation of ducts, but showed portal fibrosis with bile duct proliferation in the liver. This combination of findings is very reminiscent of those in a girl and her brother reported by Ivemark et al. (1959). The children reported here also showed absence or hypoplasia of the spleen, cardiac anomalies and other features of the Ivemark syndrome (Ivemark 1955), a quite different, usually sporadic, congenital disorder. It is suggested that the children described here have a distinct lethal congenital disorder, probably inherited in an autosomal recessive manner.

Unusual occurrence of dextrocardia with situs inversus in succeeding generations of a family

In three cases of dextrocardia with situs inversus affecting a father and his two sons, the father had married his first cousin, the daughter of his father's sister, so that the two sons were the products of a consanguineous marriage. The general and familial incidence of the condition and the genetic influences responsible for it are discussed.

Observations on some additional abnormalities in situs inversus viscerum

The abnormal findings in a case of Situs inversus totalis are described. The duodenum was placed abnormally and retained its primitive mesentery. The proximal 22 in of jejunum were retroperitoneal. The attachment of the root of the mesentery to the posterior abdominal wall had a 7-shaped appearance, and there was a partial failure of the primitive mesocolon to adhere to the posterior abdominal wall. The common hepatic artery arose from the superior meseneric artery, which also provided a branch to the proximal jejunal loop. The right vagus nerve was found anterior to the oesophagus at the oesophageal hiatus in the diaphragm, and the left vagus was posterior. A double ureter was present on the right side. The findings are discussed in relation to mid-gut development.

Familial atrial septal defect with prolonged atrioventricular conduction

This report describes a family with frequent recurrence of congenital heart disease in multiple generations. Eight members had atrial septal defect (ASD) of the fossa ovalis type and seven members had other forms of congenital heart disease. One branch of the pedigree showed a predominance of ASD with prolonged atrioventricular (A-V) conduction and initially suggested an autosomal dominant gene effect. A variety of other forms of congenital heart disease were found in several first degree relatives of those with ASD as well as in more distant relatives. The variability of congenital heart disease in this pedigree is compatible with the polygenic mode of inheritance. Definition of the inheritability of congenital heart disease in a specific family has important consequences in the determination of the recurrence risks for all family members.

Familial atrial septal defect with prolonged atrioventricular conduction. A syndrome showing the autosomal dominant pattern of inheritance

Atrial septal defect (ASD) of the fossa ovalis type was found in 16 members of one family and confirmed in 15 members at autopsy or surgery or by cardiac catheterization. Sinus rhythm was present in 12 affected members, 11 of whom had electrocardiographic evidence of prolonged atrioventricular (A-V) conduction. Five other family members without ASD also had prolonged A-V conduction. The pedigree chart suggests that the syndrome ASD with prolonged A-V conduction is the manifestation of a single mutant autosomal gene with dominant effect, a high degree of penetrance, and some variation in expressivity. Earlier reports of familial ASD showing the autosomal-dominant pattern of inheritance reveal a similar frequency of prolonged A-V conduction among affected persons. The great majority of cases of ASD are sporadic, with little likelihood of recurrence in subsequent sibs or children. We suggest, however, that when ASD of the fossa ovalis type is accompanied by prolonged A-V conduction, the genetic prognosis may be drastically changed to a risk of almost 50% that the condition will recur in subsequent sibs or children of affected persons.

Dextrocardia and isolated laevocardia. II. Situs inversus and isolated dextrocardia

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