A nomenclature is described for congenital heart disease employing sequential chamber localization. It is an eclectic system based in part upon the previous classifications of Van Praagh and Kirklin. It links together the atrial, ventricular, and arterial segments of the heart and then permits tabulation of associated anomalies. The atrial segment of the heart can exist as situs solitus, situs inversus, or situs ambiguus. Atrioventricular connexions can be concordant or discordant. In certain circumstances the terms concordant and discordant cannot be used. These are in the presence ofprimitive ventricle and in the presence of situs ambiguus. Alternative terms are described for these contingencies. Ventriculo-arterial connexions can be (a) normal; (b) transposition; (c) double outlet ventricle; or (d) single arterial trunk. These are defined as connexions; relations are relegated to secondary position. Associated anomalies are categorized in terms of venous return, atria, atrioventricular junction, ventricles, and great arteries. Controversial topics are discussed with regard to previous definitions.

SUMMARY At present there is no universally accepted nomenclature for congenital cardiac malformations. Much of the controversy results from failure to distinguish the structural connections of the heart from the morphology and spatial relations of its components. The confusion is compounded by an abundance of individual definitions, many of them speculative.The present article proposes a totally descriptive nomenclature. It describes in turn the connections of the cardiac segments, their morphology, their relations, and additional anomalies in any segment. Each step in the segmental approach is discrete. The overall effect is to force a succinct and comprehensive description of any cardiac malformation, no matter how complex.To be of value, a nomenclature must allow all congenital heart defects to be described unambiguously, accurately, and succinctly. It must assist the clinical cardiologist to diagnose and describe all these anomalies during life. It must be compatible with the morphological findings so that it is as valid for examinations at operation or necropsy as it is during diagnostic investigations. A classification and nomenclature should not be difficult to leam or to remember. Clarity, not erudition, is the touchstone of success.It is our contention that classifications at present in use do not satisfy these criteria. They lack flexibility and are frequently derived from morphogenetic concepts which are more or less speculative. In the less flexible systems, where a Procrustean approach is necessary, attempts to make them comprehensive result in sub-classifications with alphabetical and numerical designations (Edwards and Burchell, 1949) which have no descriptive value. In those based in part upon deductions from

SUMMARY In 11 necropsy specimens of pulmonary atresia with ventricular septal defect and major aortopulmonary collateral arteries, central pulmonary arteries were present in all cases, supplied by collateral arteries which anastomosed with a lobar pulmonary artery or, less commonly, with a central pulmonary artery. These normally connected pulmonary arteries frequently perfused only a minority of bronchopulmonary segments. The remaining segments were connected to collateral arteries which, within the lung, were continuous with vessels which had the structure of normally connected vessels and branched with the pre-and intra-acinar airways in a normal manner to perfuse the alveolar capillary bed. These collateral arteries and the intrapulmonary vessels with which they anastomosed had no connection, either macroscopically or microscopically, with either the central pulmonary arteries or their branches within the lung. Irrespective ofthe type ofproximal connection, the segmental pulmonary arteries were generally abnormally small. Stenoses occurred in 58-8 per cent of collateral arteries, usually as a thick-walled narrowed muscular section between the aorta and lung. Microscopically, quantitative morphometric analysis showed that within the respiratory unit the pulmonary circulation had failed to grow normally in all save the youngest patient dying at 12 days of age. The structural changes were usually consistent with a reduction in pulmonary blood flow; only three cases contained any segments of lung showing structural evidence of pulmonary hypertension. These anatomical and histological findings are discussed in relation to the embryology, nomenclature, and natural history of pulmonary atresia with ventricular septal defect and major aortopulmonary collateral arteries. The structural findings provide a rational basis for the clinical management of this condition.The preoperative assessment of pulmonary atresia with ventricular septal defect and major aortopulmonary collateral arteries has been improved by selective catheterisation of the collateral arteries. Corrective surgery is now possible using valvebearing conduits to establish continuity between the right ventricle and pulmonary circulation. The management of this condition remains imperfect, however, mainly because the anatomy of the pulmonary circulation is poorly understood. Radiological, haemodynamic, and surgical studies often provide an incomplete picture of the source of pulmonary blood supply and the intrapulmonary arterial branching pattern. In addition, the structure of the pulmonary circulation at alveolar level determines pulmonary vascular resistance and

SUMMARY At present there is no reliable method of recognising atrial isomerism by two dimensional echocardiography. We therefore used two dimensional echocardiography to examine 158 patients including 25 with atrial isomerism and four with situs inversus. Particular attention was paid to the short and long axis subcostal scans of the abdomen.Using the position of the inferior vena cava and the aorta with respect to the spine it was possible to separate those with situs solitus from the others. Two false positives for abnormal situs had exomphalos. In situs solitus the aorta lay to the left of the spine and the inferior vena cava lay to the right. One patient with situs solimus and azygos continuation of the inferior vena cava also had inferior vena cava to right atrial connection. In the four patients with situs inversus the mirror image of the normal pattern was present.In nine patients with right isomerism the inferior vena cava and aorta ran together on one or other side of the spine. The inferior vena cava, anterior to the aorta at the level of the diaphragm, received at least the right hepatic veins (normal or partial anomalous hepatic venous connection).Of the 16 patients with left isomerism, 14 had azygos continuation of the inferior vena cava which was visualised posterior to the aorta in all but two. All patients with left isomerism had total anomalous hepatic venous connection to one or both atria via one or two separate veins.Two dimensional echocardiography therefore provides the means of detecting abnormal atrial situs and of diagnosing right or left isomerism in the great majority of patients, if not all.Accurate determination of atrial situs is the foundation of a segmental approach to the diagnosis of congenital malformations and malpositions. 1 Many clinical clues are available for the recognition of patients with abnormal situs, and the importance of identifying left and right isomerism has been emphasised by many authors.5-8 A non-invasive examination such as two dimensional echocardiography which could be used routineWo determine situs would be very useful. At present, the determination ofatrioventricular connection by two dimensional echocardiography is speculative and other techniques are necessary to assign atrial situs.8-10 Alerted to the presence of abnormal situs, the echocardiographer will pay particular attention to the systemic and pulmonary venous connections.To investigate the diagnosis of situs by two dimensional echocardiography we examined 158 consecutive patients including 11 who were known to have

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