Serum lactate dehydrogenase activity and its isoenzyme patterns in patients with pectus excavatum

In previous study, we found elevated serum total lactate dehydrogenase (LDH) before correction of pectus excavatum and a decrease in total LDH after the deformity correction. In the present study, we analyzed total LDH activity and its isoenzyme patterns to investigate the causes of these laboratory findings in patients with pectus excavatum.

Between March 2014 to December 2018, 85 patients with pectus excavatum who had undergone the Nuss procedure (NP) and bar removal (BR) were included into this study. We analyzed (I) total LDH and its isoenzyme patterns before the correction, (II) relationships of total LDH and its isoenzymes with age at time of NP, sex, severity of pectus excavatum, and pectus morphology types, and (III) post-corrective changes.

The mean age of the patients was 13.6 (±6.5) years at the age of NP and the mean interval between NP and BR was 2.2 (±0.42) years. Seventy-one males and 14 females were included. The pectus types included 54 symmetric and 31 asymmetric cases. The mean Haller index before NP and BR were 3.8±1.45 and 2.7±0.4, respectively. The mean of total LDH before NP (pre-correction) and BR (post-correction) were 404.2±80.8 and 369.2±79.3 IU/L, respectively. Before correction, total LDH was significantly higher than normal values, irrespective of age [the young group (<10 years old), P=0.006, and the old group (≥10 years old), P<0.001]. The proportion of LDH5 was significantly higher than that of LDH4 (P<0.001). Total serum LDH was significantly associated with age at time of NP and Haller index (P<0.001 and P=0.030). There was no significant correlation between severity and total LDH. However, the value of only LDH5 among all isoenzymes had a significant positive correlation with severity (P=0.006) and the proportion of only LDH5 in the severe group was significantly higher (P=0.003). After correction, proportions of each isoenzyme were all within the reference range, however, there were significant decreases in values of LDH1-LDH4, except LDH5 (P=0.020, P<0.001, P<0.001, and P=0.029).

This study shows that pectus excavatum is a muscular disease entity and that laboratory findings are associated with compression of internal organs, which was explained by post-corrective changes in LDH activity and its isoenzyme patterns. This study will provide a deeper and wider comprehension of pectus excavatum.