THYMUS IN NORMAL NEWBORN AND IN CYANOTIC HEART DISEASE

Abstract

Radiological thymic size was compared in 3 groups of fullterm newborn infants in the first 2 days of llfe: Group(a)-50 normal (NNBs), Group(b)-39 severely cyanotic congenital heart disease (SCCHDs) with 21 complete D-transposition of great arteries (CTGA) 10 valvular pulmonary atresia/severe stenosis (PA), 5 tricuspid atresia(TA), 3 tetralogy of fallot (TOF) and Group(c) 21 mildly cyanotic congenital heart disease (MCCHDs) with 8 hypoplastic left heart syndrome (HLH), 13 miscellaneous complex lesions (MCL). Diagnosis in groups (b) and (c) were confirmed by cardiac catheterization and angiography. Frontal plain chest films were reviews! in all and thymic size was graded (G) as follows: absent-GO: small G1; moderate-G2 and large-G3. In NNBs 80% (40 and 50) revealed G1 to G3 thymus of which 20% were G3. In SCCHDs only 23% (9 of 39) had a thymus, all being G1 with CTGA 28.5% (6 of 21). PA 20% (2 of 10), TA 0% (0 of 5) and TOF 33% (1 of 3). In MCCHDs 62% (13 of 21) had thymus of G1/G2 (but none of G3) with HLH 75% (6 of 8) and MCL 54% (7 of 13). Thymus is often absent in SCCHDs in comparison to MCCHDs and NNBs in the first 2 days of life. The cardio-respiratory distress which accompanies HLH does not appear to alter thymic size in these infants as compared with NNBs. Level of arterial hypoxemia, which dictates the degree of cyanosis, probably is the pertinent stress factor which involutes thymus in infants with cyanotic congenital heart disease. Absence of thymus is not unique to CTGA in the newborn, but also is encountered in other types of SCCHDs.