THE INFLUENCE OF ATRIAL SIZE AND ELASTICITY ON THE LEFT ATRIAL PRESSURE TRACING

Abstract

Considerable variations in atrial size and the elastic characteristics of the atrial wall were demonstrated in cases with a comparable degree of mitral stenosis. Both these factors greatly modify the form of the indirect left atrial tracing. The Ry/V ratio is used as a numerical expression of this to compare with the variations in volume and elasticity. A simplified method of measuring the Ry/V ratio is suggested. Evidence is presented that similar if not greater variations in elasticity are present in cases of mitral regurgitation. When an enlarged atrium is easily distensible, the typical high V wave and high Ry/V ratio are absent and the tracing is indistinguishable on these criteria from those found in mitral stenosis. Four cases with an Ry/V ratio of less than 1.7 were found to have dominant mitral regurgitation. In no case of mitral stenosis, when errors in measuring the Ry/V ratio were avoided, did the Ry/V ratio exceed 1.7. Values tend to be high in small to moderate-sized atria which are comparatively inelastic, while much lower values are the rule in large-sized atria. An elevated Ry/V ratio is considered to be good evidence against the presence of significant mitral stenosis, and the larger the atrium the stronger is this evidence.