COLLAGEN CONTENT IN NORMAL, PRESSURE, AND PRESSURE-VOLUME OVERLOADED DEVELOPING HUMAN HEARTS

Increased myocardial collagen accompanies pressure overload of the adu lt left ventricle, This phenomenon is poorly understood in infants, Th is study compares the myocardial volume fraction of collagen in infant s who did not have primary heart disease with infants with isolated pr essure overload of the right ventricle (tetralogy of Fallot [ToF]), an d with infants with combined volume and pressure overload (aortic valv e atresia [AVA]). The distribution of collagen in the neonatal myocard ium was also determined, We measured the volume fraction of collagen f rom right ventricular biopsy specimens of cadaver hearts in normal inf ants (1 to 9 months old; n = 7), infants with ToF (1 day to 9 months o ld; n = 9), newborns with AVA (AVA-NB) (1 to 4 days old; n = 5), and o lder patients with AVA (AVA-I) (5 to 8 months old; n = 5). Myocordium from 3 patients undergoing repair of ToF (6 to 8 months old) was also analyzed. Specimens were stained with Masson's trichrome and myocardia l volume fraction of collagen determined by point counting, Myocardial volume fraction of collagen was significantly higher (p = 0.02) in AV A-I patients (8.0 +/- 3.5%) versus normal (3.3 +/- 2.7%), ToF (3.2 +/- 1.8%), and AVA-NB (3.5 +/- 2.3%) patients. There was a tendency for i ncreased collagen in the subendocardium, especially in AVA-I patients (p >0.05). We conclude that patients with AVA-I have increased collage n relative to normal subjects, patients with ToF, and patients with AV A-NB, and that this increase is greatest in the subendocardium.