Pulmonary Venous Index as Additional Diagnostic Criteria for Fontan Palliation

Abstract

Backgroud. The results of the Fontan operation, depending on the anatomy of the pulmonary arteries, have been studied quite well. Various indices have been proposed to assess the degree of hypoplasia of the pulmonary arterial bed (Nakata, Reddy, and McGoon indexes). At the same time, an obstruction of pulmonary venous blood return may be considered as a contraindication to Fontan operation. Aim of the Study. To present an optimal method for pulmonary venous index (PVI) calculation based on computed tomography angiography (CTA) enhancement of the heart data in patients with a functional single ventricle. Materials and Methods. 63 patients with a functional single ventricle (SV) underwent CTА (Philips, Brilliance iCT) before the Fontan operation. Axial sections were reconstructed to a thickness of 0.75–3 mm using soft tissue and lung filters, followed by postprocessing of the data (Horos and OsiriX software) and construction of multiplanar and 3D images. The diagnoses were presented by various types of SV of the heart. The age of the patients ranged from 3 to 30 years (median 7 years). Comparison of PVI was carried out in patients of two groups: those who survived the intervention (n = 55 patients) and those who died (n = 8). The evaluation of the pulmonary veins (PV) and the calculation of the pulmonary venous index (PVI) were carried out based on the measurement of each pulmonary vein at 2 levels (at the level of the orifices and bifurcation). The calculation of the PVI was carried out according to the formula: the sum of the cross-sectional area of the main pulmonary veins, related to the body surface area. 3 variants of PVI calculation were compared: taking into account the values of the PV areas at the level of the orifices, the bifurcation, and the sum of the minimum areas of each of the PVs. Results. In the group of survived patients, the median PVI at the level of the PV orifices was 292 mm/m2, and in the group of deceased, it was 242 mm/m2$\left(p=0.0326\right)$; at the level of PV bifurcation in the group of survivors, it was 299 mm/m2, and in the group of dead patients, it was 281 mm/m2$\left(p=0.0776\right)$; the minimum PVI was 257 mm/m2 in the survivor group and 218 mm/m2 in the deceased group $\left(p=0.006\right)$. An ROC analysis performed to determine the critical value of the minimum PVI affecting survival after Fontan operation revealed that PVI measured taking into account the minimum dimensions of the areas of the PV is a significant risk factor for death after Fontan operation $\left(p=0.00015\right)$, with its value (cutoff) <233.5 mm2/m2. Conclusion. The value of the minimum PVI can be an important morphological indicator of the state of PV blood return and serve as an additional criterion in determining indications for the Fontan operation.