Andersons pediatric cardiology 1123

pulmonary artery This reduces the chance of the wire dropping into the right ventricle, as is often the case when an end-hole catheter is used A multitrack catheter is less suitable to delineate supravalvar or subvalvar gradients, as the holes of the catheter are spread over several millimeters, where one hole could be above while another is at or below the subvalvar narrowing FIG 42.30 Pressure tracings of subvalvar pulmonary stenosis obtained using a pressure wire Top, Main pulmonary artery tracing Middle, Withdrawal across the pulmonary valve To the left, the tracing still has a typical arterial waveform, whereas toward the right it changes to a ventricular waveform without creating a significant gradient Bottom, After further withdrawal through the subpulmonary area, the pressure gradient becomes apparent, being virtually exclusively located at the subvalvar rather than the valvar level In patients with critical pulmonary valve stenosis or those with severe valvar stenosis and reduced right ventricular function, crossing of the pulmonary valve itself may not be well tolerated In these patients it is therefore reasonable to consider just obtaining a right ventricular-to-systemic arterial pressure ratio and delaying crossing the valve until angiography has been obtained and the balloon carefully prepped to be ready to proceed swiftly, if required Right ventricular angiography should be performed using cranial angulation with some degree of left anterior oblique projection as well as lateral projection to profile the valve's annulus The angiogram can most easily be performed in the neonate by a gentle injection of contrast by hand or, in older children, by using a right ventricular power injection (Fig 42.31) Care must be taken not to infiltrate contrast into the myocardium of the right ventricular outflow tract, as such an event can be poorly tolerated The valve's annulus is measured from hinge point to hinge point when the valve is fully open and the annulus maximally expanded (see Fig 42.31) In selected patients where there is concern about downstream stenosis located within the main or branch pulmonary arteries, rotational angiography with three-dimensional reconstruction can add valuable additional anatomic information (Fig 42.32)