Echo-phonocardiographic determination of left atrial and left ventricular filling pressures with and without mitral stenosis
Mitral Valve Stenosis
In mitral stenosis (MS) the interval between the second sound and the opening snap (A 2-OS) is known to shorten, while the interval between the onset of the QRS and the first sound (Q-M 1) lengthens with smaller mitral valve orifice size and higher left atrial pressures. Because M 1 and OS are temporally related in the C and E points on the mitral valve echogram, respectively, the ratio of Q-C to A 2-E may relate to left atrial pressure in MS and to left ventricular filling pressures (LVFP) in the absence of MS. To test this hypothesis the Q-C/A 2-E ratio was measured in 22 patients without MS from simultaneous mitral valve echogram, ECG and phonocardiogram at cardiac catheterization. An excellent correlation between Q-C/A 2-E and left ventricular end-diastolic pressure (LVEDP) was observed (r = 0.93; SEE = 2.6 mm Hg; LVEDP range 5-28 mm Hg). The resulting regression equation: LVEDP = 21.6 (Q-C/A 2-E) + 1.1, was prospectively evaluated in a second group of 32 patients without MS and with echo-phonocardiograms performed at left-heart catheterization (25 patients) or right-heart catheterization with flow-directed, balloon-tip catheters for measurement of mean pulmonary capillary wedge pressure (PCWP) (seven patients); LVFP ranged from 5-40 mm Hg. Calculated LVFP correlated well with measured LVFP (r = 0.81; SEE = 4 mm Hg). Ten of 11 patients (91%) with LVFP > 14 mm Hg were correctly separated from 19 of 21 patients (90%) with LVFP < 14 mm Hg. In 10 patients, LVFPs were acutely altered by either volume expansion or vasodilators and in all instances, calculated LVFP moved in the same direction as measured LVFP. In addition, the same equation was used to estimate mean PCWP in 22 patients with MS and eight with prosthetic mitral valves. Estimate PCWP correlated well with measured PCWP (r = 0.78; SEE = 4 mm Hg) and correctly separated 18 of 19 patients (95%) with PCWP > 18 mm Hg from nine of 11 patients (87%) with PCWP ≤ 18 mm Hg. Thus, the Q-C/A 2-E ratio and left atrial pressure correlate closely. This relationship allows one to closely estimate LVFP in patients with various types of heart disease and to judge severity of MS noninvasively.