Growth of the Pulmonary Valve Annulus after the Modified Blalock-Taussig Shunt in Patients with Tetralogy of Fallot

Background: The surgical outcomes of tetralogy of Fallot (TOF) have evolved dramatically and have resulted in lower mortality rate. Currently, the many cardiac centers have a trend to early single-stage complete repair more than a staged repair. However, the patients who have an early primary repair were required transannular patch augmentation of a pulmonary valve frequently. This effect has been developed a chronic pulmonary insufficiency may lead to right ventricular dilation, dysfunction. In this era, the aim of treatment of TOF is attempted to preserve pulmonary valve annulus for prevent right ventricular dysfunction in the future. The systemic to pulmonary artery shunt is a palliative procedure or known as staged repair for symptomatic patients with TOF. The modified Blalock-Taussig shunt (mBTS) is the most useful systemic to pulmonary shunt and perform as an initial procedure before complete repair. The mBTS can provide increase pulmonary blood flow as well as improve oxygenation and also promote pulmonary artery (PA) growth. However, the effect of this procedure to promote growth of a pulmonary valve annulus is still debate. Objectives: To compare a growth of pulmonary valve annulus between after staged repair and primary repair in patients with TOF (without pulmonary atresia). Methods: A retrospective case-control study, review of patients with TOF underwent total repair at our hospitals from January 2005 and December 2017 was performed, a total number of 112 patients underwent TOF repair. Twenty-nine patients (26%) underwent a staged repair (mBTS group) and 83 (74%) underwent total repair only or primary repair (PR group). We evaluated diameter of pulmonary valve annulus by using echocardiography at the time of first diagnosis and before complete repair on both groups. Results: The age of diagnosis of mBTS group were younger than PR group (p = 0.011). Therefore, pulmonary valve annuls were smaller in mBTS group. (Z-score, -2.93 +/- 1.42 vs. -1.89 +/- 0.97;p = 0.001). However, the growth potential of pulmonary valve annulus was increase more than PR group significantly (Z-score, -1.46 +/- 1.02 vs. -2.11 +/- 1.19; p = 0.009) Even though a patent ductus arteriosus was found commonly in PR group (p = 0.018). Conclusions: Our results suggest the systemic to pulmonary shunt or mBTS can promote growth of pulmonary valve annulus in patients with TOF.