Surgical Management of Tetralogy of Fallot with Inadequate Size Pulmonary Artery Branches
Background: Tetralogy of Fallot (TOF) with inadequate size pulmonary artery (PA) branches continues to be a problem in many developing countries due to late presentation. Surgical management is still debatable in clinical practice. Our aim is to review our experience with different surgical modalities for management of this subset of patients.
Methods: Between 2012 and 2018, out of 314 operations for TOF at our unit, there were 26 cases judged either pre-operatively or intraoperatively to have PA branches inadequate for total correction (McGoon’s ratio ≤ 1.5 or pulmonary branch size <-2 Z-value of expected size). Modified Blalock-Taussig shunt (MBTS) was done in 11 cases (shunt strategy). Open-heart surgery, involving going on cardiopulmonary bypass and cardiac arrest, was done in 15 cases (right ventricular outflow tract, RVOT, reconstruction strategy). The main PA was opened and the PA branches were sized from inside using Hegar sizers and Z-scores obtained. In 6 cases, the measured PA branches were smaller than the -2 Z-value, so, RVOT reconstruction without ventricular septal defect (VSD) closure (antegrade palliation) was done. The PA patch was adjusted to get a main PA annular diameter of not more than Z-value of -4, and to get an oxygen saturation on 25% FiO2 not exceeding 90%. In the remaining 9 cases, the sizes of the PA branches were found to accommodate a Hegar sizer within -2 Z-values. So, in those 9 patients, we proceeded to total repair with VSD closure.
Results: There were no statistically significant differences between the 2 strategies (shunt vs. RVOT reconstruction) as regarding the preoperative parameters (age, weight, preoperative oxygen saturation on room air and the preoperative McGoon’s ratio of branch pulmonary arteries size). As regarding the postoperative data, there was statistically significant difference in the total mortality being less in RVOT reconstruction (1/15, 6.6%) compared to MBTS (4/11, 36.4%). The ratio between the diameters of branch pulmonary arteries was significantly lower in antegrade palliation than with MBTS, denoting more equal and even growth of pulmonary artery branches after antegrade palliation.
Conclusion: In TOF patients judged preoperatively to have small PA branches not suitable for total correction, intra-operative direct assessment of the sizes of pulmonary artery branches by Hegar sizers is more accurate and reliable than preoperative imaging studies, and offered to save many patients from a two-stage repair allowing them a primary total repair with perfect results. In cases that needed a two-stage repair because of small PA branches, antegrade palliation yielded better early outcome than MBTS and furthermore provides uniform branch pulmonary arteries growth, which facilitates the 2nd stage total correction.