Equalization rate: a haemodynamic method for evaluation of mitral stenosis.

Abstract

The presently accepted methods for the estimation of the diastolic area of the mitral orifice have been based on either the pressure gradient (Gorlin and Gorlin, 1951) or the contour of the left atrial pressure pulse (Marshall, Woodward, and Wood, 1958). In 1961 a formula was presented in which we attempted to combine the two methods (Gunnar et al., 1961); however, the calculations had the disadvantage of producing a nondescript number which appeared to be proportional to the size of the mitral orifice as found at operation or necropsy but was without dimensions. We have now enlarged our series and modified the formula to provide dimensions which relate directly to the valve area, and the results of the analysis of this method comprise the basis of this report. SUBJECTS AND METHODSThis series consists of 74 patients with their detailed surgical reports and data from combined heart catheterization. Of these, 73 had rheumatic mitral valve disease, and one had a congenital cleft of the mitral valve associated with a previously repaired persistent ostium primum defect.(1) Estimates of Orifice Area at Surgery. It became apparent early in our study that surgical estimates of orifice size were relatively inaccurate. In "closed" procedures, the amount of a precisely measured "finger" which can be partially or completely passed through an orifice is a crude measurement and depends upon the delicacy of the initial examination. The surgeon may apply more pressure than the atrio-ventricular gradient, and adhesions may be severed by the examining finger. In "open" procedures and at necropsy the ragged edges of a deformed mitral valve and the uneven planar apposition of the mitral leaflets make estimations difficult despite direct observation (Richter, 1963). Recognizing these limitations, we divided all the surgical estimates of orifice size into four categories.Group I included cases with "tight" stenosis or orifices measuring 1 cm.2 or less. Group II included cases with "moderate" stenosis or orifices measuring 1 1l to 2-0 cm.2 Group III included cases of "mild" stenosis or orifices measuring 2-1 to 3-0 cm.2 Group IV consisted of cases in which the orifice measured more than 3 cm.2 (2) Catheterization Techniques. Combined heart catheterization was performed in all cases. A modification (Bougas, Musser, and Goldberg, 1956) of the Bjork (Bjork, Malmstrom, and Uggla, 1953) technique was used. A Cournand catheter was inserted in a peripheral vein and advanced into the right pulmonary artery. The patient was turned into the prone position and two 18-gauge, thin-walled cardiac needles were inserted transthoracically under fluoroscopic guidance into the left atrium. Two polyethylene *