Morphologic Substrates for First-Branch Pulmonary Arterial Hypoplasia in Transposition of the Great Arteries

Abstract

Background: Distal right-sided outflow obstruction remains a problem after arterial switch operation. We studied the anatomical features of the pulmonary trunk (PT) and its branches that are susceptible to right and left pulmonary arterial (RPA and LPA) hypoplasia in transposition of the great arteries (TGA). Methods: One hundred and one angiograms of TGA performed between 1981 and 1996 were viewed, and Polaroid photos were taken at end-systole. The diameters of RPA, LPA, PT, duct, ascending aorta, and angles between PA and PT were measured, and the ductal flow direction was recorded. Results: Forty-eight cases (47.5%) had a PA/PT diameter ratio (both PAs had same size) below 0.49. A smaller PA/PT was significantly related to posterior inclination of the proximal PT [narrower right (r = 0.50, p < 0.00001) and left (r = 0.48, p < 0.00001) PA-PT angle in lateral view] and a larger duct (r = 0.37, p < 0.0001). Eighteen patients had a follow-up angiogram after a mean period of 8.5 months. Those with a closed duct had evident PA growth (n = 12, 0.51 ± 0.09 to 0.74 ± 0.17, p < 0.0001), but four patients with an attenuated duct had no significant change (0.58 ± 0.06 to 0.68 ± 0.08, p = NS), and one with a persistent large duct had even regression of PA/PT (0.36–0.19). The direction of ductal flow was toward the aorta during early systole on cineangiogram. Conclusions: First-branch PA hypoplasia, which is frequently seen in TGA, was related to the right-to-left shunt through a duct resulting in hemodynamic starvation, and to posterior inclination of the proximal PT in this setting. Natural regression of the duct facilitated PA growth.

Abnormal Pulmonary Artery Bending Correlates With Increased Right Ventricular Afterload Following the Arterial Switch Operation

“…On the other hand, while the conventional measurements in our study were consistent with reported literature, 8,25 they only take into account PA stenosis and do not correlate with RV afterload. Our novel measurements (R c , R c-w , and bending angle) quantify a phenomenon previously observed via angiography and described by Chen et al 26 and Chiu et al 27 as "narrowing of the pulmonary arch window." The abnormal curvatures and bending angles in the branch pulmonary arteries are likely an effect from multiple geometrical components, particularly enlargement of prox-AscAo and a rightward MPA position.…”

“…As shown in Table 4, conventional measurements of PA size (Nakata index, RPA/total area ratio) correlated with differential pulmonary blood flow (r ¼ 0.49, P ¼ .0011) and did not correlate with RV afterload (r ¼ À0. 26…”

Restoration of Transposed Great Arteries to Nature

“…Central PA hypoplasia, which is frequently seen in TGA, is related to posterior inclination of the proximal MPA in this setting. 28 We have also showed that the same pathogenesis would lead to smaller PA size after a Senning operation than ASO with Lecompte maneuver. In addition, Lecompte with Pacifico’s modification (direct connection between the distal MPA and the aortic sinus defect), which mobilized the proximal MPA toward the anterior aspect farther than did the patch repair of the sinus defect, could facilitate better PA growth after ASO.…”

Restoring the spiral flow of nature in transposed great arteries

“…Its pathogenesis was related to a posterior inclination of the proximal MPA in this setting (Fig. 1A) [8]. To facilitate PA growth, it is best to mobilise the posterior inclination of the proximal MPA and restore its 'normal' position ( Fig.…”