MORPHOMETRY OF THE FIBROUS RING OF THE MITRAL-VALVE

In standard textbooks of anatomy it is generally accepted that the fib rous ring of the mitral valve lies in a single plane throughout its en tire circumference. Some authors have stated otherwise, but there are no morphometric studies.30 formalin-fixed hearts were sectioned to rev eal the shape of the fibrous ring of the mitral valve and studied by m orphometric, radiographic and histological methods. It was noted that the fibrous ring adopted a horizontal ''S'' shape around the two commi ssures and the average distance between the highest and lowest parts o f the fibrous ring was found to be 7.1 mm (range 6.2-12.5 mm). Radiogr aphic evaluation revealed that the fibrous ring lies approximately in two planes rather than in one. Histological study showed that the fibr ous tissue of the mitral valve is continuous with the aortic fibrous r ing, and that a slight but significant thickening marks the insertion of the mitral valve. The mitral valve thus lies in two planes, and it is hoped that this information will contribute to cardiac and valvulop lastic surgery.