Enzymatic activities in heart and skeletal muscle of children with cyanotic and noncyanotic congenital heart disease.

The activity of phosphofructokinase (PFK), citrate synthetase (CS), lactate dehydrogenase (LDH), 3-OH-CoA dehydrogenase (ACDH) and cytochrome-c-oxidase (cyt-ox) was measured in right atrial auricle and abdominal rectal muscle biopsies from 24 children, aged 3-12 years, with congenital heart malformations. Twelve children had cyanotic conditions (tetralogy of Fallot or truncus malformations) and 14 were noncyanotic (septal defects or vascular lesions). The cyt-ox activity was significantly higher in the cyanotic subgroup than in the noncyanotic (skeletal muscle: 55.71 +/- 10.4 vs 19.48 +/- 2.6 mmol/g protein/min, p less than 0.01; auricle: 93.1 +/- 11.8 vs 65.58 +/- 7.5, p less than 0.05). There were no significant differences between the activities of PFK, LDH, CS or ACDH in the cyanotic and noncyanotic groups. Within the normal range of hemoglobin and hematocrit, there was no correlation between these parameters and cyt-ox. On the other hand, above the normal range of hemoglobin and hematocrit a correlation coefficient of 0.89 (p less than 0.01) was observed which suggests the higher cyt-ox activity to be an adaptive phenomenon triggered by reduced availability of oxygen.