Right heart chambers and atria have higher baseline collagen concentrations than left chambers and ventricles, and left ventricular collagen is not necessarily increased by atherosclerosis or hypertrophy.
The collagen concentrations of the four cardiac chambers of normal hearts were determined chemically. Right ventricles and atria contained significantly higher collagen concentrations than did left ventricles and atria. The atria contained twice the collagen concentration of the ventricles. Severe atherosclerosis, hypertrophy and coronary occlusion did not necessarily increase the concentration of collagen in the left ventricle of diseased hearts.
Oken et al. (Mon,) studied this question.