SummaryWith Value of Angiocardiography in Tetralogy of FallotInfundibular StenosisThe recognition of an organic pulmonary infundibular stenosis is important. It occurred in 76% of the cases. I t is usually at the crista, and in the sagittal plane, but tends to be in the coronal plane, and more horizontally if very low. It may be “band‐like”, but more often it appears as a “tight” constriction.In fundibular ChamberThe next most favourable group for surgery are those with a high or intermediate pulmonary infundibular stenosis and a small chamber (Group 2).The most difficult group surgically is the group with a high pulmonary infundibular stenosis and no chamber (Group 3), A larger proportion of these cases have pulmonary valve stenosis in addition to pulmonary infundibular stenosis, and many also have hypoplasia of the outflow tract from the valve ring onwards. (Sec paragraph below.)Pulmonary Valve Stenosis (36 cases in all)This occurred in about half of the cases with pulmonary infundibular stenosis, i.e., 19 cases, or and incidence of about 31%. It also occurred isolated in the groups with muscular pulmonary infundibular stenosis (Group 4) and double outlet right ventricle (Group 5), 28% Total incidence, about 60%.In the former group, a “muscular” type of infundibular stenosis was recognized which the surgeon described as “not a true organic pulmonary infundibular stenosis”. This is when there is no definite evidence of a localized constriction, there is a very labile outflow tract with more variation in size than in the groups above, or a very trabeculated outflow tract. In almost all these case the muscular hypertrophy in the outflow tract and in the right ventricle was found to be secondary to pulmonary valve stenosis, with in many cases hypoplasia of the main pulmonary artery and of the pulmonary artery branches also. Thus this group can be considered as pure pulmonary valve stenosis–20%Hypoplasia or Coarctation of the Main Pulmonary Artery and Pulmonary Artery Branches Distal to the Valve (25%)It is very important to recognize such cases, as they are less favourable surgically and a patch may be required. Supra‐valvular narrowing is the commonest type of main pulmonary artery stenosis, But coarctation of the branches is common, often involving both branches, and often not recognizable without angiocardiography. In many of these cases the surgeon has had to place a patch in the outflow tract in addition to performing a pulmonary valvotomy. The risk of surgery is thus much greater in this group, particularly in cases under the age of four years.Double outlet Right Ventricle — with Absent Crista (8%)In many cases a fairly certain diagnosis of this can be made, and if not the surgeon should be warned of this possibility. These cases had muscular hypertrophy of the infundibulum and right ventricle and all had pulmonary valvestenosis also.Ventricular Septal DefectThis was usually infra‐cristal, or Type 2. Supra‐cristal defects should be watched for. However, the left anterior oblique projection is preferable for the anatomy of the septa1 defect.Overriding or Dextroposition of AortsAgain this is best demonstrated in the left anterior oblique projection. A record of the amount of dextroposition was made in about half the cases, but was abandoned later as it was found that the correlation between this and the degree o f cyanosis, i.e. severity of the condition and the anatomy of the infundibular stenosis was very poor.However, extreme dextroposition should be noted as it may approximate to or resemble a double outlet right ventricle.Associated AnomaliesThese should also be watched for, e.g. anomalous coronary artery (Case 13, Figure 6).In many of these cases the recognition of an infundibular chamber above the constriction is a valuable guide to the presence of an organic pulmonary infundibular stenosis. A chamber was present in 29% of the cases if a low pulmonary infundibular stenosis can if a low pulmonary infundibular stenosis can be recognized, and especially if this chamber can be seen, as in group 1 and group 2, it is very likely that there will be no valvular stenosis or hypoplasia of the out flow tract beyond If the chamber is large, as in Group 1, there is never a distal obstruction beyond this, i.e. no valve stenosis, and the surgeon does not need to consider the possibility of having to insert a patch. In all cases where there is a chamber the anatomy is favourable, and the larger the chamber the smaller the risk. In all our patients who have had a complete repair of the Fallot's tetralogy and pulmonary valvular stenosis, the long‐term r