Andersons pediatric cardiology 1067

FIG 40.19 Representative measurements of oxygen saturations (A; in percent) and pressures (B, in mm Hg) obtained during cardiac catheterization in a patient with common arterial trunk There is evidence of a substantial left-to-right shunt, with the oxygen saturation in the pulmonary arteries, exceeding that in the caval veins Nonetheless, the oxygen saturation in the aorta exceeds that in the pulmonary arteries because of streaming Pressures in the right and left ventricles are equal, and there is no evidence of stenosis of the truncal valve The pressure that was measured in the left pulmonary artery is slightly less and that in the right pulmonary artery and significantly less than that in the aorta, reflecting a stenosis of the origin of the right pulmonary artery Measurements of pressure will reveal, in the typical case, similar pressures in the right and left ventricles There may be minor differences between the measurements in the two pulmonary arteries, and between the pulmonary arteries and the aorta, which may reflect streaming Pressure differences may also reflect obstruction at the point of origin of pulmonary arteries from the aorta, or in one pulmonary artery Such differences in pressure between the aorta and the pulmonary arteries may be found in almost half of the patients.33 Any differences in systolic pressure should be noted across the truncal valve These occur in one-third of patients and vary from 10 to 60 mm Hg Nonetheless, minor differences in pressure are common and reflect excessive flow, rather than truncal stenosis Selective angiocardiography should be performed, first, in the truncal root, filming in frontal and lateral projections Elongated right anterior oblique views show well the division of the aortic and pulmonary pathways from the trunk.34 Rapid injections of contrast are necessary to avoid excessive dilution of the contrast medium by the torrential flow Such an injection should demonstrate the anterior tilt of the truncal root, the origin of one or both pulmonary arteries from the ascending trunk, and the degree of truncal regurgitation The arteries can also arise from other unusual sites, such as one of the truncal sinuses An injection in the truncal root will usually demonstrate any interruption of the aortic arch and should also reveal any unilateral absence of one pulmonary artery, an association found in between one-tenth and one-sixth of patients If suspected, a further descending aortogram, and selective injection(s) into collateral arteries, or even pulmonary venous wedge injections on the side of the absent pulmonary artery, should clarify whether the artery really is absent, or whether it originally derived its blood supply from an arterial duct Surgical Treatment Early attempts at surgical palliation involved banding the pulmonary arteries, either at the level of a confluent pulmonary arterial segment, or separately for the right and left arteries This procedure has now been almost completely abandoned, in favor of complete, early surgical repair The first such complete repair of common arterial trunk, using a nonvalved conduit, was at the University of Michigan in 1963, whereas the more commonly used approach of repair using a valved conduit to restore continuity from the right ventricle to the pulmonary arteries, was achieved at the Mayo Clinic in September 1967.35,36 Both pulmonary arteries are dissected down to their points of branching in the hilums of both lungs The aorta is fully mobilized The surgery is performed under hypothermic cardiopulmonary bypass The degree of truncal incompetence is carefully assessed Significant regurgitation may interfere with myocardial protection In cases of significant truncal valve regurgitation, direct administration of cardioplegic solution into the coronary artery origins or the use of retrograde cardioplegia via the coronary sinus may be necessary The pulmonary arteries are detached from the common trunk, taking care to avoid any coronary arterial origins The defect in the aorta may be closed by direct suture, or with a small patch of synthetic material, homograft, or pericardium If there is no confluent pulmonary arterial segment, access is improved by transecting the ascending component of the common trunk The separate pulmonary arteries are excised with the interposed portion of trunk as a single button, and the ascending aorta is reconstructed as an end-to-end anastomosis The ventricular septal defect is closed with a patch in such a way as to connect the remaining aortic component of the trunk with the left ventricle Continuity between the pulmonary arteries and the right ventricle can often be established with the aorta cross-clamped while the patient is being rewarmed With adequate mobilization of the pulmonary arteries, it should be possible to anastomose a valved conduit, usually a homograft, directly onto the right ventriculotomy without any prosthetic interposition (Video 40.12) Because the availability of homografts may be limited, and to avoid the longterm problems of homograft stenosis, modifications to the procedure have been described that avoid their use In one such modification, continuity between the right ventricle and pulmonary arteries is achieved without use of a conduit This