Symposium on Pediatric Cardiology

Incidence, Etiology, and Classification of Congenital Heart Disease

Beverly C. Morgan, M.D. *

The reported incidence of congenital heart disease varies to some extent from one country to another, but in general the major determining factor is the interval over which data are obtained. In some newborn ;series, an incidence of less than 1 per 1000 live births has been reported. With long-term follow-up, however, the incidence is about 6 per 1000.! The incidence of congenital heart disease appears to be independent of geographic or other differences. When similar methods are utilized, including criteria for diagnosis, sufficient follow-up, and other such important factors, similar data are obtained. An incidence of between 6 and 8 per 1000 live births is the usual figure reported. The etiology of congenital heart disease remains obscure in most cases. Recognized teratogens (thalidomide, antimetabolites, maternal rubella infection, and so forth) have been identified. Maternal age and parity do not appear to be a major determinant except in unusual instances, such as the common occurrence of congenital heart disease in patients with Down's syndrome. Infants of diabetic mothers have an increased incidence of congenital heart disease, with 1 in 20 such infaIlts being afflicted. 2 The overall sex ratio for infants with congenital cardiovascular malformations approximates 1: 1, but sex ratios differ in specific malformations. The common persistency of patency of the ductus arteriosus in premature infants, both with and without lung disease and/or ventilatory support, is significantly increased over that of the normal term newborn infant. Cardiovascular malformations are rarely determined by clearcut genetic patterns. Chromosomal disorders, such as Down's syndrome, trisomies 15 and 18, and Turner's syndrome, are commonly associated with congenital heart defects. The majority of patients with congenital heart disease are otherwise normal, although renal anomalies, usually mild, occur with increased frequency. Careful studies have suggested that genetic-environmental interaction (multifactorial inheritance) accounts for approximately 90 per cent of the cases of congenital heart disease with 1 to 2 per cent being environmental (rubella and other 'Professor and Chairman, Department of Pediatrics, University of Washington School of Medicine, Seattle, Washington

Pediatric Clinics of North America' - Vol. 25, No.4, November 1978

721

722

BEVERLY

C, MORGAN

teratogens) and 8 per cent being primarily genetic (5 per cent chromosomal and 3 per cent single mutant gene),3 Evaluation of the recurrence of congenital heart disease in families with one affected member is important 'in family counseling. The risk of recurrence is in the range of 2 to 4 per cent, assuming the absence of a mendelian syndrome or an unusual family history.4 In general, one can be encouraging to the patient with congenital heart disease and to their family members regarding reproduction since a high probability exists for these individuals to have normal children. The ·differential diagnosis of congenital heart disease should be done with an organized, systematic approach. Some authors prefer a classification based on the presenting sign of more common heart malformations in the first month of life. 5 Others utilize an anatomic classification (l-p 684-6). We have found useful a classification with the initial determinant being the presence or absence of cyanosis since this physical finding, confirmed by Pa02 and/or hematocrit values, presents a helpful initial point for classification. This information, together with a careful physical examination, estimation of pulmonary blood flow in chest film, and electrocardiographic findings, makes it possible, in many cases, to develop a relatively short list of possible diagnoses with a fairly high degree of accuracy (Table 1). Further diagnostic studies (such as echocardiography and cardiac catheterization/angiography) are performed promptly to confirm the clinical impression if significant symptoms develop. These additional studies are often indicated electively when confirmation of a diagnosis is required. However, a careful attempt to establish the diagnosis by routine techniques (Table 1) not only may prevent unnecessary studies with risk involved but will also contribute, at least to a moderate deTable 1. Classification of Congenital Heart Disease _ _ _ _ _ _ CYANOTIC

~

Decreased

Severe pulmonary stenosis Pulmonary atresia

(with or without

-J,

Pu'mona~

JH Tricuspid atresia Pulmonary atresia with hypoplastic fight ventricle

I/SO')

Flow

~rCVH Transposition with pulmonic stenosis Truncus arteriosus with hypoplastic pulClonary a rter i es

Increased pUlmonaty Blood Flow

~

lVH,

Aortic atresia; hypoplastic ,left heart

R~.

or CVH

Transposition Single ventricle Tricuspid atresia with transposition

syndrome

Total anomalous manary venous

Transposition a rteri es

great

ACYANOTIC

t

Increased Pu 1mona (LBl ood Flow

~-~--

Coarctation Mitral stenosis

R"/H U",-I

CVH VSD PDA ASD

Coarctation Aortic stenosis Endomyocardial disease (endocardial fibroelastosis. myocarditis) r'1itral regurgitation

right ventricular hypertrophy left ventricular hypertrophy cOJi1bined ventricular hypertrophy ventricular septal defect patent ductus arteriosus atrial septal defect

Lvt

Atrial septal Patent ductus arteriosus defect Ventricular septal defect All left-to-rig/:lt Arteri ovenous fi s tul a shunts with pulmona ry hypertens i on, i.e., PDA, VSD, ASD

INCIDENCE, ETIOLOGY, AND CLASSIFICATION

723

gree, to the important efforts to contain escalating health care costs, In addition, it is very rewarding to the physician to use clinical skills effectively in the diagnosis of any disease,

REFERENCES 1. Nadas, A, S., and Fyler, D. C.: Pediatric Cardiology. Edition 3. Philadelphia, W. B. Saunders Co., 1972, ch. 13. 2. Mitchell, S. C., Sellmann, A. H., Westphal, M. C., et al.: Etiologic correlates in a study of congenital heart disease in 56,109 live births. Am. J. Cardiol., 28:653,1971. 3. Nora, J. J.: Multifactorial inheritance hypothesis for the etiology of congenital heart disease: The genetic-environmental interaction. Circulation, 38 :604, 1968. 4. Nora, J. J., and Nora, A. H.: Recurrence risks in children having one parent with a congenital heart disease. Circulation, 53:701, 1976. 5. Rowe, R. D., and Mehrizi, A.: The Neonate with Congenital Heart Disease. Philadelphia, W. B. Saunders Co., 1968, ch. 7. Department of Pediatrics University of Washington School of Medicine Seattle, Washington 98195