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Collagen content in normal, pressure, and pressure-volume overloaded developing human hearts
S M Schwartz1, D Gordon, R S Mosca
1Department of Pediatrics, The University of Michigan Medical School, Ann Arbor, USA.
Insights
Infants with aortic valve atresia (AVA) show higher myocardial collagen than healthy infants or those with tetralogy of Fallot (ToF). This increase in collagen, a key heart tissue component, is most pronounced in older AVA patients and the subendocardium.
Area of Science:
- Cardiovascular Research
- Pediatric Cardiology
- Cardiac Pathology
Background:
- Myocardial collagen increases with pressure overload in adults, but this is poorly understood in infants.
- Congenital heart defects in infants can cause pressure or volume overload, affecting heart tissue composition.
Purpose of the Study:
- To compare myocardial collagen volume fraction in infants with normal hearts, isolated right ventricular pressure overload (tetralogy of Fallot), and combined volume/pressure overload (aortic valve atresia).
- To determine the distribution of collagen within the neonatal myocardium in these conditions.
Main Methods:
- Analysis of right ventricular biopsy specimens from cadaver hearts of normal infants, infants with tetralogy of Fallot (ToF), and infants with aortic valve atresia (AVA) at different ages.
- Masson's trichrome staining and point counting method to quantify the myocardial volume fraction of collagen.
Main Results:
- Myocardial collagen volume fraction was significantly higher in older infants with aortic valve atresia (AVA-I) (8.0%) compared to normal infants (3.3%), ToF infants (3.2%), and newborns with AVA (AVA-NB) (3.5%).
- A trend towards increased collagen was observed in the subendocardium, particularly in AVA-I patients.
Conclusions:
- Infants with severe aortic valve atresia (AVA-I) exhibit increased myocardial collagen compared to normal, ToF, and AVA-NB groups.
- The subendocardium shows the greatest increase in collagen in affected infants, suggesting a specific regional response to cardiac overload.
Abstract:
Increased myocardial collagen accompanies pressure overload of the adult left ventricle. This phenomenon is poorly understood in infants. This study compares the myocardial volume fraction of collagen in infants who did not have primary heart disease with infants with isolated pressure overload of the right ventricle (tetralogy of Fallot [ToF]), and with infants with combined volume and pressure overload (aortic valve atresia [AVA]). The distribution of collagen in the neonatal myocardium was also determined. We measured the volume fraction of collagen from right ventricular biopsy specimens of cadaver hearts in normal infants (1 to 9 months old; n = 7), infants with ToF (1 day to 9 months old; n = 9), newborns with AVA (AVA-NB) (1 to 4 days old; n = 5), and older patients with AVA (AVA-I) (5 to 8 months old; n = 5). Myocardium from 3 patients undergoing repair of ToF (6 to 8 months old) was also analyzed. Specimens were stained with Masson's trichrome and myocardial volume fraction of collagen determined by point counting. Myocardial volume fraction of collagen was significantly higher (p = 0.02) in AVA-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 increased collagen in the subendocardium, especially in AVA-I patients (p > 0.05). We conclude that patients with AVA-I have increased collagen relative to normal subjects, patients with ToF, and patients with AVA-NB, and that this increase is greatest in the subendocardium.