Ultrastructural quantification of collagen in human chordae tendineae

Objective-To determine collagen fibril diameter distributions in the chordae tendineae and to see whether there are any differences between right and left sides of the human heart. Design-Collagen fibril diameters and the percentage volume occupied by collagen fibrils (as opposed to ground substance) were determined by means of a planimeter with a digitising tablet from electron micrographs printed at a magnification of 136; 000. Material-Human chordae tendineae were obtained at postmortem examination from seven subjects aged 50-75 years. Measurements and main results- Histograms of collagen fibril diameter distributions showed a sharp, unimodal distribution. The mean collagen fibril diameters associated with the tricuspid and mitral valves were 41·1 nm and 40·5 nm respectively. The percentage volume occupied by collagen was about 39% for each valve. There were no significant differences for any of these values between the right and left sides of the heart. Conclusions-The greater pressures present on the left side of the heart are not reflected in any difference in collagen fibril diameters within the chordae tendineae compared with the right side.