Use of the Valvular Resistance in the Separation of Normal and Stenotic Hancock Mitral Valves

Recent data suggests that the pressure-flow relationship for normal bioprosthetic mitral valves is linear. If this is correct, the valve resistance may provide a better indicator of normal mitral function than the Gorlin valve area. We compared the Gorlin valve area to the valve resistance (calculated as flow/pressure) in order to determine which better separated normal and stenotic Hancock mitral valves. Measurements were made using left atrial and left ventricular catheters in 42 patients undergoing Hancock mitral valve replacement. Patients were studied during pacing and isoproterenol infusion for a total of 141 measurements. Stenotic Hancock mitral valve hemodynamics were obtained at cardiac catheterization from eight patients who were studied at rest and during atrial pacing and from an additional eight patients culled from the literature (a total of 23 stenotic measurements). The Gorlin valve area ranged from 1.1 to 4.4 cm2 for the normally functioning Hancock valves and from 0.4 to 1.54 cm2 for the stenotic valves. Six measurements in patients with confirmed stenotic valves yielded Gorlin areas larger than the lowest area found in the normal valves and no value of the Gorlin valve area correctly classified all of the normal and the stenotic valves. The valve resistances of the normal valves ranged from a minimum of 1.0 to a maximum of 5.1 (mean 2.9 ± 0.8) while the resistances of the stenotic valves ranged from 6.6 to 38 (mean 12.9 ± 8.2). There was no overlap of the normal and the stenotic measurements. The valve resistance, which is based on a model of normal mitral valve physiology, appears to better separate normal and stenotic Hancock mitral valves than the Gorlin area, which is based on a model of stenotic valvular flow.