Unbalanced atrioventricular septal defect with dominant right ventricle: diagnostic criteria, indications for biventricular correction, and results. A clinical observation series

Relevance: Surgical treatment for congenital heart disease (CHD) with borderline left ventricle (LV) dimensions is one of the most challenging issues in current pediatric cardiac surgery. Despite the prevailing general trend to the expansion of indications for biventricular repair of an unbalanced atrioventricular septal defect (AVSD) with a dominant right ventricle (RV), the diagnostic criteria for imbalance, feasibility of radical repair and its functional results are intensively discussed in the literature.

Aim: To present quantitative criteria for the assessment of the LV size which could serve as an indication for biventricular repair of the right dominant unbalanced AVSD.

Materials and methods: We present a  series of 4  patients with AVSD and dominant RV, who underwent radical repair of the defect. The mean age of the patients was 2.4 years, and 3 of 4 had concomitant CHD: tetralogy of Fallot, double outlet right ventricle with pulmonary artery stenosis, and moderate hypoplasia of the aortic arch with subaortic stenosis. Three of 4 patients had previously undergone palliative interventions: two of them – pulmonary bending, one, the first stage of univentricular repair (atrioseptostomy, cavopulmonary anastomosis). Two children had been diagnosed with Down syndrome. The mean left ventricular end diastolic diameter (LVEDD) at baseline was 17.9 mm, corresponding to Z score of -5.4.

Results: All four patients underwent biventricular repair of the defect with a  two-patch technique. In one case, it was supplemented with placement of the pulmonary trunk homograft prosthesis, in the other with pulmonary valve commissurotomy and cavopulmonary anastomosis due to moderate tricuspid valve stenosis and in the third case the mitral valve was replaced. In 3 patients pacemaker implantation was performed. The criterion for feasibility of complete septation was the ratio of the longitudinal dimensions of the left and right ventricles (LAR > 0.7), confirmed by computed tomography performed before the surgery. The mean LVEDD after surgery was 28.3 mm, corresponding to Z score of -0.8. At the time of the hospital discharge, the left and right atrioventricular valves insufficiency did not exceed 2 and 1 degrees, respectively.

Conclusion: Computed tomography allows for accurate measurement and comparison of the longitudinal dimensions of the heart ventricles with LAR index as a tool for assessment of the LV size before the biventricular repair. An additional prospective study is required to objectify the data obtained and identify predictors of an unfavorable outcome of radical repair in patients with right dominant unbalanced AVSD.