demonstration of concordant atrioventricular and discordant ventriculoarterial connections The atrioventricular connections can readily be examined using subcostal and apical four-chamber views Anterior angulation of the transducer then demonstrates the discordant ventriculoarterial connections Specifically, the bifurcating pulmonary trunk can be demonstrated originating from the left ventricle, and the aorta, which is usually anterior, from the right (Fig 37.11) Parasternal imaging reveals the relationships of the arterial trunks Typically, the aortic valve is positioned anterior and to the right of the pulmonary valve (Fig 37.12) FIG 37.11 Cross-sectional images obtained from a subcostal window in a patient with transposition (A) Anterior angulation demonstrates the bifurcating pulmonary trunk (PT) arising from the left ventricle (LV) (B) Further angulation demonstrates the aorta arising from the right ventricle (RV) In this patient, the aortic valve is anterior and to the right of the pulmonary valve Ao, Aorta FIG 37.12 Cross-sectional image obtained from the parasternal window demonstrating the anterior and rightward position of the aortic valve (AV) relative to the pulmonary valve (PV) (Courtesy Dr Joshua Kailin, www.pedecho.org.) Having demonstrated the basic anatomic connections, other aspects can readily be appreciated Juxtaposition of the atrial appendages (most commonly left juxtaposition of the right appendage) can be demonstrated from apical, parasternal, or subxiphoid windows (Video 37.2) Additional subxiphoid, apical, and parasternal views, combined with the use of color Doppler interrogation, should be used to confirm or exclude the presence of a ventricular septal defect and demonstrate the direction of associated shunting A detailed examination of the pulmonary valve and the left ventricular outflow tract is an essential part of the preoperative assessment because any significant obstruction to the left ventricular outflow may influence surgical management The atrioventricular valves should be assessed carefully to identify any abnormal attachments of the tendinous cords A detailed assessment of the origin and course of the coronary arteries should routinely be performed prior to surgical intervention This requires interrogation from multiple views and is aided by a familiarity with the common arrangements in transposition (Fig 37.13) Determining intramurality of a coronary artery is challenging but is suggested when the vessel passes between semilunar valves or has a high take-off from the aorta.37 Patency of the arterial duct and the direction of ductal shunting should be confirmed These features are best visualized from the suprasternal and high sagittal views, sweeping between the aorta and pulmonary artery The aortic arch should always be assessed in detail to exclude coarctation or interruption As it is difficult to exclude coarctation in the presence of a widely patent arterial duct, repeat studies should be considered to reassess the arch after the prostaglandin infusion is discontinued FIG 37.13 Images obtained from a subcostal window demonstrating the coronary arteries (A) Anterior angulation demonstrates the course of the circumflex artery (circ.) (B) Further angulation demonstrates the right (Rt.) and left anterior interventricular arteries (LAI) originating from a common origin The atrial septum and the degree of interatrial shunting are best visualized using subcostal windows The demonstration of a small interatrial communication, deviation of the atrial septum towards the right atrium or highvelocity left-to-right flow on pulsed wave Doppler, should immediately suggest the presence of restriction at the interatrial communication, particularly in a severely cyanosed infant However, it is important to note that normal septal alignment or the absence of high-velocity flow across the septum does not necessarily mean that all is well Rather, in the presence of an inadequate atrial communication, blood may simply travel across the mitral valve into the left ventricle, never creating a left atrial to right atrial pressure gradient Cardiac Catheterization Cardiac catheterization is no longer routinely performed; all necessary anatomic information may be obtained from cross-sectional echocardiography There is still an occasional role for cardiac catheterization in the assessment of the