Annex A > Chapter 3 - Developments in the UK, in the Diagnosis and Treatment of Congenital Heart Abnormalities in Children, 1984-1995 > The specific heart abnormalities and procedures referred to in the Inquiry > Complete Atrio-Ventricular Septal Defect (CAVSD)

Complete Atrio-Ventricular Septal Defect (CAVSD)

Figure 5: Complete Atrio-Ventricular Septal Defect

The problem

49 The defect involves the whole area of the junction of the upper and lower chambers of the heart, i.e. where the atriums join the ventricles. There is a large hole between the lower portion of the atriums and the upper or `inlet' portion of the ventricles and this is associated with a significant abnormality of the valves separating the atriums from the ventricles. The valves in effect become a common atrio-ventricular valve, and the severity of the defect depends largely on the supporting attachments of the valve to the ventricles and whether the valve allows dominant flow from the right atrium to right ventricle and from left atrium to left ventricle. The overall problems are similar to those of VSD but are more complicated. There is an increased flow of blood to the lungs through both the ventricular and atrial components of the defect. In addition, the abnormal atrio-ventricular valve invariably leaks, so that when the ventricles contract, blood flows not only forwards to the body and the lungs, but also backwards into the atriums. The back-pressure effect on the atriums causes congestion of blood in the left atrium in particular, and this in turn causes congestion in the veins draining the lungs. The effect on the baby is to worsen the heart failure that is associated with an isolated VSD and to hasten the onset of pulmonary hypertension. It should be mentioned that CAVSD is found in approximately one-third of babies who have Down's syndrome, but it also occurs as an isolated abnormality.

Diagnosis

50 The symptoms are similar to those of VSD with breathlessness, difficulty in feeding and failure to gain weight. The diagnosis may be anticipated by examining the baby and by a characteristic abnormality of the electrocardiogram (ECG) but the confirmation is obtained by echocardiography. In the present day, and even from the mid-1980s to the mid-1990s, a complete diagnosis could usually be made by echocardiography alone. From the late 1980s onwards, technological advances have helped to improve the accuracy of recognising all components of the abnormality. In some cases, it may also be necessary to do cardiac catheterisation in order to assess the question of pulmonary hypertension and to obtain a clearer impression of whether the two ventricles are each of adequate size to allow for surgical closure of the defect.

Management

51 The initial management is the medical treatment of heart failure and usually
tube-feeding in order to encourage growth. The surgical procedure is a complicated open-heart operation involving closure of the defects between the atriums and the ventricles, and separation of the common atrio-ventricular valve into two separate valves. Since the time when surgical treatment first became possible, it has been recognised that surgical correction is the ideal approach, preferably during the first few months of life in order to cure the heart failure and to prevent the high incidence of the progression of pulmonary hypertension.

52 In the mid-1980s cardiologists and surgeons were faced with the quandary of knowing that surgical correction of CAVSD carried a high risk, especially in babies under the age of 1 year. There was a tendency to delay the operation until the baby had grown because it was considered that the risk would then be lower. However, it was recognised that this was often at the cost of the baby developing irreversible pulmonary vascular disease (pulmonary hypertension) in which case an operation was no longer possible.

53 Towards the beginning of the 1990s changes in the operative technique and probably other factors in management of care led to a significant reduction in reported mortality and by the mid-1990s most centres in the UK were able to achieve good results.

54 It is important to recognise that even after an apparently successful corrective operation, problems can continue for children with CAVSD. Usually these relate to a continued leak back through the atrio-ventricular valve from the left ventricle to left atrium. In those cases, later surgical repair or even replacement of the valve may become necessary, often some years after the original operation.

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