Quantitation of Mitral Regurgitation by Doppler Echo

ABSTRACT & COMMENTARY

Synopsis: Peak mitral inflow E velocity is a readily available and widely applicable estimate of MR severity by echo-Doppler.

Source: Thomas L, et al. J Am Coll Cardiol 1998;31: 174-179.

Despite considerable research efforts, the estimation of mitral regurgitation (MR) severity by echo-Doppler remains a challenge. Thus, Thomas and colleagues sought to test the hypothesis that MR severity is proportional to mitral inflow E-wave velocity, since MR increases early diastolic left atrial pressure. Thomas et al retrospectively evaluated the echocardiograms from 102 patients with isolated mild-to-severe MR in sinus rhythm. The measurements evaluated included peak E- and A-wave velocity, E/A ratio, and E deceleration time. The gold standard for MR severity was regurgitant fraction (RF) calculation by echocardiography. Peak E-wave velocity correlated best with RF (r = 0.52, P < 0.001), and a peak E greater than 1.2 m/s identified severe MR with a sensitivity and specificity of 86%. Also, a dominant A-wave pattern was not seen in any patient with severe MR. The presence of a reduced left ventricular ejection fraction (< 50%) did not alter the value of peak E for identifying patients with severe MR, nor did age or heart rate. E/A ratio, peak A velocity, and E deceleration were less well correlated with RF and much less discriminant between MR severity groups. Thomas et al conclude that peak mitral inflow E velocity is a readily available and widely applicable estimate of MR severity by echo-Doppler.

COMMENT BY MICHAEL H. CRAWFORD, MD

Most echocardiographic laboratories use jet morphology to estimate the severity of MR, but this method is known to be imprecise—especially with eccentric or wall hugging jets, which may underestimate MR severity. In such cases, other factors are considered, such as left ventricular and atrial size and pulmonary venous flow patterns. In clinical situations where severity information is critical, quantitative echo-Doppler techniques can be applied, such as RF, regurgitant area, and proximal isovelocity surface area. However, these techniques are time consuming and have their own problems in certain patients.

Thus, often several qualitative factors are assessed together to estimate MR severity. Another simple measure is welcome if it can contribute to such an estimate or stand on its own. It appears that the simple concept of E-wave velocity can do both and could identify patients with potentially severe MR in whom further evaluation with quantitative techniques is warranted.

Improved methods for detecting moderate or severe MR are needed because of the problems with all current techniques and the importance of the clinical situation. We have learned that in order to preserve left ventricular function, it is necessary to operate "early" on MR, sometimes before symptoms occur. The consensus is that patients with even mild symptoms and moderate MR should be considered for surgery. Patients with severe MR should be considered even if they are essentially asymptomatic. Thus, the distinction between mild, moderate, and severe MR is clinically important. It appears from this data that peak E velocity is best at separating severe MR from lesser grades.

One caveat to measuring peak E velocity is that E velocity varies with the distance from the mitral anulus and can be altered by changes in anular size. Thus, measurements should be made at the mitral leaflet tips with a 5-10 mm sample volume.