Congenital abnormalities of the heart occur in approximately 8 per 1000 live births. Some of these malformations are haemodynamically trivial, but others cause mortality and major morbidity in early childhood in developed countries. About 30 per cent cause symptoms in the early months after birth. As palliative and corrective surgery become increasingly effective more individuals will reach adult life with significant congenital heart lesions; many require further surgery. In order to understand the types and effects of cardiac abnormalities it is necessary to consider modern descriptive terminology before considering physiological consequences.

Sequential chamber analysis is a way of describing the morphological arrangement of any heart in a logical manner without making reference to known or conjectured embryological processes which have given rise to the situation. If systemic veins drain normally into a morphological right atrium, pulmonary veins drain normally to a morphological left atrium, each atrium drains through an appropriate valve into a morphologically concordant ventricle and each ventricle gives rise to an appropriate great artery, the heart is said to have normal connections. Having normal connections is not inconsistent with the heart being in an abnormal position, and the majority of congenital heart defects are found in a normally connected heart. Abnormality of connection at any level (atrial, ventricular, arterial) should be clearly and precisely described always referring to right or left in a morphological rather than a positional sense. Thus atrial situs solitus means usual atrial arrangement with a morphologically right atrium being to the right of the morphological left atrium, whereas in atrial situs inversus there is a mirror image arrangement of the atria with the morphological right atrium being to the left of the morphological left atrium. Atria and ventricles have certain characteristics which allow their morphological recognition clinically as well as surgically. Recognition of the morphology of particular cardiac chambers in life is most readily achieved by ultrasound imaging but electrocardiography, radiography, and angiocardiography may all provide helpful information. Once morphological connections have been described any abnormalities in the relative position of structures can be given, for example aorta to left of pulmonary artery. Table 1 488 gives a simplified outline of normal and abnormal connections based on the work of Anderson and others. Van Praagh's system of segmental analysis has many similarities to sequential chamber analysis and is widely used in North American literature; it is rather more complex and relates to embryological processes. When the basic arrangement of a heart has been described further lesions can be elucidated, for example stenosed valves or septal defects. Another more traditional and complementary way of describing and classifying heart defects is by basic physiological disturbances.

Congenital heart abnormalities can be grouped together by their physiological characteristics, thereby allowing general statements to be made about the adverse effects of the lesion. Some abnormalities fit into several physiological groups.

Six physiological divisions will be considered: obstructive and regurgitant lesions, left to right shunts, right to left shunts, common mixing situations, transposition haemodynamics (Table 2) 489, and functional as opposed to structural heart disease.

A simple obstruction such as arterial valve stenosis or coarctation will result in hypertrophy of the cardiac chamber proximal to it, usually without gross dilatation of the chamber initially, particularly in pulmonary or aortic stenosis, but not in mitral stenosis (a rare congenital lesion) which does produce left atrial enlargement. Regurgitation of a valve is far more likely to produce dilatation of the proximal chamber and consequent radiographic evidence of enlargement of the heart. Both pressure and volume overload of a chamber may eventually result in adverse effects further back in the circulation than the chamber immediately proximal to the lesion. Isolated obstructive lesions will not alter the amount of blood passing through the lungs: there needs to be an abnormal gap (atrial or ventricular septal defect) or persistence of a normal gap (patent foramen ovale in critical pulmonary stenosis in the newborn) for this to occur.

The common lesions thus classified are atrial and ventricular septal defects, atrioventricular septal defects, and patent ductus arteriosus. In patients with uncomplicated disease blood flows from left to right heart at a rate determined by the size of the hole and the pressure drop across it. Thus, very little blood will cross even a large ventricular septal defect until the normal postnatal fall in pulmonary vascular resistance occurs. Hence, such a defect is frequently not suspected in a newborn, who may present with a murmur or heart failure some weeks later. High pulmonary blood flow can cause heart failure as the left ventricle becomes volume overloaded by the increased pulmonary venous return in those with ventricular septal defect, patent ductus arteriosus, and atrioventricular septal defects. Volume overloading from atrial septal defects occurs chiefly to the right ventricle, and heart failure in childhood is rare. So called ostium primum atrial septal defects are correctly classified as partial atrioventricular septal defects and as such may be associated with heart failure in infancy. High pulmonary blood flow or high pressure perfusion of the pulmonary vascular tree may result in permanent constriction of the pulmonary arterioles with consequent elevation of pulmonary vascular resistance. In this event, right-sided pressures may exceed left heart pressures and right to left shunting occurs producing cyanosis (Eisenmenger complex). The likelihood of Eisenmenger haemodynamics and its timing varies from lesion to lesion, being early and almost universal in complete atrioventricular septal defects and only exceptionally encountered in simple ostium secundum atrial septal defects. Much rarer left to right shunting lesions include aortopulmonary window and coronary arteriovenous fistula.

Because right heart pressures are normally lower than left after the first few days of life right to left shunting occurs if there is both obstruction to blood flow through the right heart and a route for the blood to cross to the left such as an atrial or ventricular septal defect. In young infants a patent foramen ovale allows such shunting to occur. The net result of this arrangement is that desaturated blood bypasses the lungs and reaches the systemic circulation to produce systemic arterial desaturation and probably recognizable cyanosis, depending on the degree. Examples of right to left shunting lesions are given in Table 2 489.

Mixing of desaturated and fully oxygenated blood results in a degree of systemic arterial desaturation, the severity of which will depend chiefly on whether there is increased or decreased lung blood flow. Mixing can occur at any level from before venous blood drains into the heart (for example total anomalous pulmonary venous drainage to the superior vena cava) until when blood leaves the heart (as in truncus arteriosus). Tricuspid atresia (absent right atrioventricular connection) exemplifies a lesion in which two of these physiological mechanisms coexist, with right to left shunt and common mixing.

Transposition exists when the aorta arises from the right ventricle and the pulmonary artery arises from the left ventricle (ventriculoarterial discordance). Clearly there has in transposition to be some mixing of systemic and pulmonary blood to sustain life: this can be at atrial, ventricular, or great arterial levels. Other lesions such as obstruction (pulmonary stenosis) or obligatory common mixing (tricuspid atresia) may also be present.

Functional congenital heart disease includes bradyarrhythmias and tachyarrhythmias in the absence of macroscopic structural abnormalities, myocarditis, and cardiomyopathy already present at birth.

Fetal ultrasound examination is increasingly being used to detect cardiac abnormalities from about 18 weeks gestation onwards. Routine screen of all pregnancies is not common in the United Kingdom at present, but examination of certain groups at increased risk is frequently requested. Parents of an affected previous child may request antenatal scanning: for most couples the recurrence risk is only about 3 per cent. Detection of other fetal abnormalities may result in cardiac abnormalities being sought. Professional and parental views on termination of pregnancy vary and are beyond the scope of this contribution. Increasing numbers of babies are being born with cardiac abnormalities diagnosed antenatally. Delivery may require selection of facilities and experienced staff. Fetal arrhythmias producing hydrops fetalis may occur in the presence of structurally normal or abnormal hearts.

Congenital heart disease may present in the early weeks of life in a number of ways. A cardiac abnormality may be revealed by investigation (ECG or ultrasound) before it is clinically apparent, the investigation having been undertaken for some other reason, such as Down's syndrome or oesophageal atresia. Heart failure in a young baby causes sweatiness, breathlessness, and poor feeding. Physical signs include tachycardia, tachypnoea, intercostal indrawing, and hepatomegaly. Peripheral oedema is a very late feature of neonatal and infant heart failure, and the jugular venous waveform and pressure cannot be reliably evaluated. Cyanosis is only a sign of gross heart failure, although some conditions causing heart failure may also cause cyanosis. Congenital cardiac abnormalities causing heart failure in the newborn and in infancy are given in Table 3 490. Acquired heart disease such as myocarditis may also cause heart failure in this age group as in any other.

Central cyanosis can be difficult to recognize in newborn infants, particularly if they are plethoric, even by newborn standards, if they have facial petechiae after birth (traumatic cyanosis), or if they are of non-white race (Fig. 1) 1669. Cyanosis of hands and feet is very common in healthy babies in the first few days of life. Cyanosis may be caused by respiratory disease, in which case respiratory distress is usually very marked. Some improvement is often seen when high concentrations of oxygen are breathed; blood gases analysis reveals hypercapnia and chest radiographs allow a diagnosis to be made. If doubt still exists an ECG and a formal hyperoxia test may help, but cardiac ultrasound scanning is likely to be needed. Cyanosis may also be a feature of hypoglycaemia, hypocalcaemia, and various abnormal neurological states, the mechanisms for these involving respiratory depression or elevated pulmonary vascular resistance, Methaemoglobinaemia causes a baby to look a slate blue colour: this is easily confused with central cyanosis but arterial oxygenation is rarely abnormal, even though the blood itself is black. Cardiac causes for cyanosis can be classified into three main categories: common mixing, right to left shunting, and transposition. Some congenital lesions fall into more than one category. Generally speaking, babies with common mixing conditions without associated obstruction to blood flow into the lungs are likely to be less desaturated and are not as deeply cyanosed newborns; those with transposition without a large associated ventricular septal defect or patent ductus arteriosus present very early in life. Infants with conditions associated with high rates of lung blood flow develop heart failure. A list of cyanotic lesions is given in Table 2 489.

Murmurs in newborn babies and infants may be normal innocent noises; serious congenital heart disease can also exist in the absence of murmurs. Nevertheless much store is placed on listening for murmurs at routine examinations. History and other features of the physical examination are important in helping to determine whether further investigation of a murmur is needed. Arterial valve stenosis causes a murmur which may be heard from birth; left to right shunting lesions usually do not as the shunt will be small until pulmonary vascular resistance falls. An innocent murmur arising from the pulmonary arteries may be heard over the upper chest and laterally at birth and for the first few months of life. Tricuspid regurgitation secondary to perinatal asphyxial stress may cause a transient pansystolic murmur at the lower left sternal edge; a small ventricular septal defect may cause an identical murmur in the newborn period. This has a high likelihood of disappearing, with the defect closing in the first year of life.

Newborn babies and older infants may collapse due to sepsis and many other causes, but arrhythmias (with or without structural heart disease) and congenital heart lesions must be borne in mind, particularly if collapse occurs in the first week or two of life and is associated with cardiomegaly and hepatomegaly. Infants with lesions in which the systemic circulation is dependent upon patency of the ductus arteriosus present with collapse; there may have been earlier concern about developing heart failure or poorly felt femoral pulses, but this is not the rule. Lesions associated with duct dependent systemic circulation are listed in Table 4 491. If pulmonary blood flow is critically dependent on the ductus arteriosus cyanosis will appear or worsen when the duct closes. Collapse with respiratory distress will follow if severe hypoxaemia results in metabolic acidosis before appropriate intervention occurs (Table 5) 492.

Abnormality of the femoral pulses such as impalpability or diminished pulse pressure compared with upper limb pulses should always be sought when assessing the cardiovascular system of young babies. Difficulty in feeling femoral pulses suggests coarctation of the aorta: the diagnosis can be confirmed or excluded by upper and lower limb blood pressure measurement and investigation.

Heart failure and cyanosis (Fig. 2) 1670 are unusual presentations of congenital heart disease beyond infancy, but they may be features of the progressive natural history, particularly as modified by surgery. Occasionally a patient with Eisenmenger haemodynamics from an unrecognized ventricular septal defect or patent ductus arteriosus may present with cyanosis in later childhood or adult life; heart failure in middle age is a manifestation of some congenital lesions which may have escaped earlier detection, such as atrial septal defects or coarctation of the aorta. Sinus of Valsalva aneurysm does not cause symptoms until rupture in adult life causes heart failure. Hypertension and cerebrovascular accidents in young adults are a presentation of coarctation. Syncope, especially on exertion, angina, or even sudden death may be the first indication of congenital left ventricular outflow obstruction. ‘Funny turns’ due to arrhythmias associated with congenital heart lesions may result in previously unrecognized conditions, such as atrial septal defect or congenitally corrected transposition, being detected. Infective endocarditis may be the presenting feature of a congenitally bicuspid aortic valve. Asymptomatic murmurs in childhood are frequently innocent but can be due to a large number of structural heart lesions. Many of these are important indicators for prophylaxis against endocarditis. Some, including aortic stenosis, coarctation, patent ductus arteriosus and atrial septal defect, are of major haemodynamic importance. The most common innocent, normal murmurs in children over the age of 1 year are a venous hum and the vibratory midsystolic murmur described by Still. Features of these murmurs are given in Table 6 493; and in both of these conditions cardiovascular examination is otherwise normal.

This yields extremely valuable information on rhythm, chamber size and dominance, and myocardial state. Echocardiography is more sensitive at determining left ventricular hypertrophy. There are certain ECG patterns which are almost diagnostic in particular clinical settings: left axis deviation in a cyanosed neonate with oligaemic lung fields makes tricuspid atresia virtually certain, while a superior, ‘north west’ QRS axis in Down's syndrome points to a complete atrioventricular septal defect.

As originally described this test helps distinguish cyanotic congenital heart disease in the newborn from respiratory disease by the fact that cyanotic heart disease is not usually associated with a rise in arterial oxygen tension above 20 kPa in an infant breathing FIo&sub2; of 0.85 or greater.

The availability of ultrasound imaging has reduced the need for the hyperoxia test, but it is still useful where ultrasound is not readily available. It is also useful in alerting the physician to the presence of more complex cardiac disease in an infant who is not clearly cyanosed but who may still not respond normally to breathing a high concentration of oxygen. Persistent pulmonary hypertension of a newborn with a structurally normal heart may cause a failed hyperoxia test, although the response may be labile. Hyperoxia testing can be performed using transcutaneous oxygen tension electrodes if no other indication for arterial sampling exists and a conclusive result (pass or fail) is obtained.

Echocardiography has revolutionized the investigation and management of congenital heart disease. M-mode echocardiography, ultrasound imaging, and Doppler in all its modalities (continuous wave, pulsed wave, and colour flow) allow precise anatomical and functional information to be obtained by experienced operators (Figs 5 and 6) 1673,1674. An increasing number of patients are referred to surgery without the need for invasive investigation. Intraoperative ultrasound scanning shows promise in reducing the incidence of unexpected complications or unsatisfactory repairs by allowing their detection in the operating theatre. Transoesophageal, as opposed to praecordial, scanning is useful in studying atrial anatomy but is not practicable in very young children at present.

This is often used to evaluate haemodynamics and eludicate anatomical details, but these roles are being modified rapidly by echocardiography. Although mortality and morbidity rates are low they must be weighed against the benefit to be gained in a particular case. Interventional cardiac catheterization is finding an increased role in congenital heart disease (Fig. 7) 1675 and is making some operations, such as pulmonary valvotomy, a rarity (Table 8) 495.

Anatomical details are clearly displayed by MRI, although to date clear clinical advantage over ultrasound or angiography is only recognized in a few conditions, such as locating pulmonary arteries in patients with truncus arteriosus or pulmonary atresia with ventricular septal defect. Information on cardiac output and pulmonary vascular resistance can be obtained from magnetic resonance studies but whether this will supersede assessment with ultrasound techniques remains to be seen.

Choice of the correct investigations at the right time needs careful judgement taking into account risks and benefits as well as the age of the patient and the degree of co-operation required and likely to be obtained. A knowledge of the possible natural histories of conditions subject to corrective or palliative surgery is not always available and careful repeated follow-up by clinical and investigational means is required. Investigations with minimum hazard, inconvenience, and expense should be used whenever possible.

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