Histopathologic Changes After Pulmonary Artery Banding for Retraining of Subpulmonary Left Ventricle.

BACKGROUND:In patients with congenitally corrected transposition of the great arteries (ccTGA) with an intact ventricular septum (IVS) or d-looped transposition of the great arteries (DTGA) with IVS after an atrial switch operation, left ventricular dysfunction often develops after anatomic repair despite previous retraining of the morphologically left ventricle (mLV) by using pulmonary artery banding (PAB). This study examined histopathologic changes in such mLVs. METHODS:Capillary density, myocyte diameter, and interstitial fibrous area in the mLV were retrospectively evaluated in postmortem or explanted heart specimens obtained from patients with ccTGA with IVS or DTGA with IVS after atrial switch operations after PAB for retraining and were compared with those of patients with normal cardiac anatomy, ccTGA with IVS or DTGA with IVS without PAB, and ccTGA or DTGA with high mLV pressure by using generalized estimating equations models. RESULTS:Adjusting for age, capillary density in 4 patients with ccTGA with IVS or DTGA with IVS after PAB was approximately 20% lower than that in 8 patients with normal cardiac anatomy (3149 ± 863/μm2 vs 3978 ± 1206/μm2 [mean, SD]; P = .039), whereas myocyte diameter was approximately 50% larger (16.2 ± 4.0 μm vs 11.7 ± 2.4 μm [mean, SD]; P < .001). The interstitial fibrous area did not differ between the 2 groups (803 ± 422 μm2 vs 789 ± 480 μm2; P = .92). CONCLUSIONS:The study investigators observed significant cardiomyocyte hypertrophy but lower capillary density in patients with ccTGA with IVS or DTGA with IVS after PAB for retraining compared with normal control subjects. This finding suggests that inadequate capillary growth is a potential pathologic basis for mLV dysfunction occurring after retraining or anatomic repair.