Direct left atrial pressure tracings and the degree of mitral obstruction.

Attempts have been made to assess the degree of mitral obstruction in mitral stenosis by analysing the diastolic part of indirect left atrial pressure tracings (Owen and Wood, 1955). These pressure tracings have been obtained using a cardiac catheter in the pulmonary artery in the " wedge " position, and available evidence suggests that direct left atrial pressure tracings are comparable to indirect tracings in this measurement (Connolly et al., 1953; Owen and Wood, 1955; Dickens et al., 1957). Owen and Wood (1955) state that the behaviour of the y descent (or Ry/v*) provides evidence of the presence or absence of obstruction at the mitral orifice, a slow y descent suggesting obstruction, and a sharp y descent absence of obstruction. The present study is an attempt to analyse Ry/v in cases of surgically proven mitral stenosis before and after mitral valvotomy.