PHYSIOLOGICAL INTERPRETATION OF THE PLAIN RADIOGRAPH IN MITRAL STENOSIS, INCLUDING A REVIEW OF CRITERIA FOR THE RADIOLOGICAL ESTIMATION OF PULMONARY ARTERIAL AND VENOUS PRESSURES.

1. An assessment of the accuracy of different groups of criteria for estimating pulmonary arterial and venous pressures from the plain radiograph in mitral stenosis has been made. 2. The degree of pulmonary vascular resistance has been related to the radiological appearances of the lung fields. 3. The relationship of “B” lines to pulmonary arterial and venous pressure has been studied. 4. Evidence supporting Simon's (1958) hypothesis of high and low pressure groups in venous hypertension is advanced and appropriate pressure ranges suggested for each of the six grades. 5. A set of diagrams for assessing pulmonary artery and pulmonary venous pressure from the plain radiograph in mitral stenosis has been presented.