PULMONARY-ARTERY GROWTH AFTER SYSTEMIC-TO-PULMONARY SHUNT IN CHILDRENWITH A UNIVENTRICULAR HEART AND A HYPOPLASTIC PULMONARY-ARTERY BED - IMPLICATIONS FOR FONTAN SURGERY

The aim of the study was to investigate the developmental pattern of h ypoplastic pulmonary artery (p.a.) bed augmented by systemic-to-pulmon ary shunt in children with univentricular heart scheduled for Fontan s urgery. For the study, a highly selected patient cohort was chosen (12 patients aged between 5 and 19 years; mean 9.5 years) with comparable initial morphological conditions of univentricular heart and hypoplas tic p.a. bed, who after mandatory systemic-to-pulmonary shunt underwen t Fontan procedure at time of normalization of pulmonary artery size. Further selection criteria were: normal pulmonary vascular resistance at time of Fontan procedure, competent av valve(s), and globally unimp aired ventricular function. All patients were grouped according to the preoperative pulmonary flow index (Qpi; L/min/m(2) b.s.a.) measured i mmediately before Fontan operation: Group A: 1.5-2.5; B: 3.0-4.0; C: 4 .0-5.0; D: > 6.0, and their cardio-pulmonary hemodynamic situation (Hb , SAsat%, Qp/Qs, PAP, Rp/Rs, EDVP, FS%, ventricular diastolic complian ce (VC = EDVP/Qpi + Qsi) as well as the pulmonary artery size and area using standard Nakata-index, McGoon-ratio) and a self designed comput er assisted planimetric area calculation (PPAAI; cm(2)/m(2) b.s.a.) an alysed. Each patient underwent 1-3 shunt procedures, the mean shunt pa tency period for groups A, B, C and D was 12, 8.6, 5.3, and 4.5 years, respectively. The mean Nakata-index (283, 297, 324, 405 in groups A-D ) and the McGoon-ratio (2.0, 2.2, 2.8, 3.3 in groups A-D) correlated w ith the Qp index, reflecting flow dependent development of pulmonary a rtery bed. No correlation was found between Qpi and PPAAI (47, 40, 41 and 47 in group A-D). The VC/Qp relation showed an inversely proportio nal pattern with values 2.3, 1.0, 0.8, 0.7 for corresponding groups A- D, the lowest VC in group A correlated with polyglobulic status (Hb- v alues; g/dl) : 21.3 in A vs 19.8, 18.0 and 16.5 in ED) and mean arteri al SAsat-values (77% in A vs 83%, 84% and 89% in B-D). In conclusion, in our highly selected patient cohort, the development of p.a. size wa s strongly flow-dependent, and patients with restrictive pulmonary flo w needed an approximately threefold longer time period to normalize th eir p.a. size compared to those with excessive flow. In patients with restrictive pulmonary flow, the Nakata-index underestimated the degree of development of the pulmonary artery system, probably due to the di stortion of the proximal p.a. segment. In consequence, in these patien ts the normalization of the p.a. bed and thus suitability for the Font an procedure probably occurred much earlier. Based on our observations and those of others, in patients with excessive flow the normalizatio n of p.a, bed, provided it occurs within 3-4 years, seems not necessar ily to be associated with a deterioration of ventricular function.