FIG 43.12 Continuous Doppler trace through the tricuspid valve of an infant with pulmonary atresia and intact ventricular septum There is highvelocity tricuspid regurgitation, with a peak velocity of more than 5 m/s, indicative of suprasystemic right ventricular pressures The RV should be assessed to determine its overall size and the degree of mural overgrowth (Fig 43.13) A judgment should be made as to whether the cavity possesses all three of its components, or only one or two (Videos 43.2 and 43.3) In our experience, the right ventricular cavity may seem smaller echocardiographically than it appears angiographically, largely because the apical trabecular zone may seem completely obliterated when, in reality, there are intertrabecular spaces The presence of tiny ventricular septal defects should be noted An assessment of the patency of the infundibulum should be made (Video 43.4), particularly from the subcostal paraoblique view The atresia may be membranous (Fig 43.14) or muscular depending on the extent of muscular mural hypertrophy The presence of any forward or retrograde flow across the pulmonary valve should be assessed to exclude critical pulmonary stenosis or functional atresia The presence of any fistulous communication to the coronary arteries should be sought (Fig 43.15; Video 43.5) FIG 43.13 Echocardiograms showing the four chambers and illustrating the range in size of the right ventricular cavity (A) Tripartite right ventricle of near-normal size (arrow) with minimal mural hypertrophy (B) Unipartite right ventricle with considerable mural hypertrophy and obliteration of the cavity (arrow) FIG 43.14 Echocardiograms showing an imperforate pulmonary valve suitable for balloon perforation (A) Parasternal short-axis view in ventricular diastole demonstrating normal appearance of the valve leaflets (B) Imperforate valve in systole, with excursion of the fused valvar leaflets This is the echocardiographic equivalent of the morphologic specimen shown in Fig 43.3 AV, Aortic valve; PA, pulmonary trunk; PV, pulmonary valve; RV, right ventricle (From Abrams DJR, Rigby ML, Daubeney PEF Membranous pulmonary atresia treated by radiofrequency-assisted balloon pulmonary valvotomy Circulation 2003;107:e98–e99.) FIG 43.15 Parasternal short-axis echocardiographic image showing fistulous communications from the right ventricle to the right coronary artery The pulmonary trunk and branches should be measured to ascertain their size, and the source of blood flow to the lungs determined Normal pulmonary venous return should be confirmed Structure and function of the left ventricle should be assessed, including regional abnormalities of mural motion Following such investigations, it should be possible to decide whether the long-term strategy is for biventricular as opposed to univentricular repair, and to plan the initial intervention Cardiac Catheterization and Angiography In addition to echocardiography, from a diagnostic perspective, cardiac catheterization and angiography may be helpful in the evaluation of an infant with this lesion, particularly to assess the size of the RV and the presence and severity of fistulous communications The usual approach is via the femoral vein because it can be difficult to enter the RV from the umbilical vein.58 The latter