has less clinical relevance today, when transthoracic echocardiography is routinely used to follow and evaluate patients with pulmonary valve stenosis Rudolf proposed that, in children, the voltage of a pure R wave recorded at V1 correlates with approximately 20% of the right ventricular pressure.25 It turns out that the QRS axis may be a more reliable indicator of right ventricular pressure.26 Indeed, the prediction of right ventricular pressure gradient is optimized by use of a number of variables in addition to the measurements of voltage on the ECG, as proposed by Ellison,27 as follows: The clinical score included presence of cyanosis, worth 25; pulmonary component of the second sound, worth 15 if diminished (or 25 if inaudible); a QRS axis of greater than 90 degrees, worth 10; negative T waves in aVF and V1, worth 35; and RV1 above 10 mm worth 15 This complex formula has been superseded by the quicker, more accurate, and more reliable use of Doppler echocardiography Chest Radiograph The chest radiograph shows the features of right ventricular hypertrophy and, if present, poststenotic dilation of the pulmonary trunk Right ventricular hypertrophy is seen as an upturned cardiac apex The dilated pulmonary trunk is seen as a prominence of the left upper heart border, inferior to the aortic knuckle (Fig 42.12) Right atrial enlargement causes a more pronounced convexity of the right lower heart border Although it is important to know those findings, a routine chest radiograph is usually not indicated in the evaluation of patients with pulmonary valve stenosis FIG 42.12 Frontal chest radiograph of mild pulmonary stenosis showing a prominent pulmonary trunk without features of right ventricular hypertrophy Echocardiography The gold standard investigation for the assessment of the morphology of pulmonary stenosis is cross-sectional echocardiography coupled with Doppler analysis of the flow in the right ventricular outflow tract and pulmonary arteries Advantages such as widespread availability and lack of adverse side effects have helped make echocardiography the primary imaging modality by which pulmonary stenosis is diagnosed and managed Cross-sectional echocardiography will define whether the obstruction is at the level of the valvar leaflets (Fig 42.13; Video 42.1) or subvalvar (Fig 42.14) or supravalvar (Fig 42.15) The presence and severity of restricted motion of the leaflets as well as dysplasia can readily be assessed, along with any poststenotic dilation of the pulmonary trunk (Fig 42.16) The diameter of the pulmonary valve at the hemodynamic ventriculoarterial junction can be measured accurately (Fig 42.17), facilitating the planning of intervention Attempts have been made to quantify these methods, with recommendations being published on how to measure the pulmonary outflow tracts and semilunar valves in the pediatric population Specifically, the pulmonary valve annulus should be magnified in the parasternal long- or short-axis view and measured between the inner edges of the hinge points in midsystole.28 Although routinely done in valvar pulmonary stenosis, echocardiographic measurement of the pulmonary valve annulus does not preclude the need to measure by angiography during intervention, as echocardiographic measurement appears to underestimate annular size.29 FIG 42.13 Two-dimensional image of the pulmonary valve in the parasternal short-axis view from a patient with valvar pulmonary stenosis Note the thickened leaflet tips of the pulmonary valve ... to quantify these methods, with recommendations being published on how to measure the pulmonary outflow tracts and semilunar valves in the pediatric population Specifically, the pulmonary valve annulus should be magnified in the parasternal long- or short-axis view and measured between the inner edges of the