Does the modified Blalock-Taussig shunt cause growth of the contralateral pulmonary artery?

Background. Although some pediatric cardiology departments have a policy of adopting primary correction of tetralogy of Fallot in all symptomatic infa nts, we and others still palliate neonates and infants. Effective palliatio n should ameliorate symptoms and allow growth of the pulmonary arteries. Al though studies on the growth of the ipsilateral and contralateral pulmonary arteries after a classic Blalock-Taussig shunt have been reported, pulmona ry artery growth after a modified Blalock-Taussig shunt has not been studie d as thoroughly. Therefore, we examined whether there is equal growth of th e contralateral pulmonary artery after a modified Blalock-Taussig shunt. Methods. We retrospectively analyzed the records of 140 patients with sympt omatic tetralogy of Fallot who had a modified Blalock-Taussig shunt between October 1985 and October 1995. The median age at the time of the Blalock-T aussig shunt was 1.6 months. All patients had corrective procedures at a me dian age of 1.7 years. Cineangiography was done before the corrective proce dure. From the angiograms the diameter of the right and left pulmonary arte ries before their first lobar branches and the diameter of the descending t horacic aorta at the level of the diaphragm were measured. For each patient the ratios of right pulmonary artery to descending thoracic aorta and left pulmonary artery to descending thoracic aorta were determined and compared using Student's t test. Results. Of the 140 patients, 114 had a left-sided Blalock-Taussig shunt, 2 0 had a right-sided shunt, and 6 patients had bilateral shunts. The mean ri ght pulmonary artery to descending thoracic aorta ratio was 1.10 and the me an left pulmonary artery to descending thoracic aorta ratio was 0.98. This difference was not significant. Conclusion. We showed equal growth of the right and left pulmonary arteries with no distortion after a modified Blalock-Taussig shunt. If palliation i s considered, the modified Blalock-Taussig shunt remains our choice. (Ann T horac Surg 1999;67:1397-9) (C) 1999 by The Society of Thoracic Surgeons.