Doppler-echocardiographic evaluation of left atrial contribution to left ventricular filling in mitral stenosis at rest and during exercise

Left Atrial Contribution to Left Ventricular Filling in Patients with Mitral Stenosis: Combined Analysis of Transmitral and Pulmonary Venous Flow Velocities

We recorded transmitral and pulmonary venous flow velocities using transthoracic continuous-wave and transesophageal pulsed Doppler echocardiography, respectively, in 36 patients with mitral stenosis who were in sinus rhythm to investigate the left atrial contribution to left ventricular filling in mitral stenosis. The mitral valve area was determined by transthoracic two-dimensional short-axis echocardiography. Patients were classified as having mild stenosis (>/=1.5 cm(2), n = 17) or moderate stenosis (<1.5 cm(2), n = 19). The mean pulmonary capillary wedge pressure and left atrial maximal diameter were significantly larger, and left atrial volume change during atrial contraction was significantly smaller in the moderate group than in the mild group. The percent left atrial contribution to left ventricular filling, estimated from the transmitral flow velocity, the peak atrial systolic velocity, and the percent ratio of left atrial systolic regurgitation to left atrial filling, estimated from the pulmonary venous flow velocity, were significantly lower in the moderate group than in the mild group. The percent left atrial contribution to left ventricular filling, the peak atrial systolic velocity, and the percent ratio of left atrial systolic regurgitation to left atrial filling were positively correlated with the mitral valve area and negatively correlated with the mean pulmonary capillary wedge pressure. These results suggest that the left atrial contribution to left ventricular filling in patients with mitral stenosis in sinus rhythm decreases as the severity of valve stenosis increases, and that analysis of the atrial systolic waves of the transmitral and pulmonary venous flow velocities provides important information for evaluation of left atrial systolic performance in patients with mitral stenosis.

[Usefulness of exercise Doppler in the diagnosis of severe mitral stenosis]

BACKGROUND

Exercise in mitral stenosis produces an increase in cardiac output and heart rate which determines the increment in the transmitral gradient. However, it has not yet been established what level is reached by the gradients on exercise in severe mitral stenosis nor whether the rise in the gradient during such exercise is different to that occurring in non-severe stenosis.

OBJECTIVE

To evaluate the effect of exercise in patients with severe mitral stenosis on the mitral valve gradients in absolute values and on the increment with respect to base values.

METHODS

Forty-eight mitral stenosis patients (mean age: 48.8 +/- 11 years) underwent 50 exercise Doppler echocardiographic studies using supine bicycle ergometry in two stages with increases of 25 W every 3 minutes; from each of these we obtained the peak and mean mitral gradient using a non-imaging continuous-wave Doppler probe. We also conducted this procedure on 14 patients with a mean age of 50 +/- 6 who had Bjork mitral prostheses which were functioning normally.

RESULTS

We defined a hemodynamic profile of severity based on the data from 18 patients whose basal mitral valve areas was < 1.2 cm2 (group I), and compared them with the data from the 32 studies of mitral stenosis patients with an area > 1.1 cm2 (group II) and with the patients with mitral prostheses (group III). The mean mitral gradient (mmHg) in group I was greater than in group II at rest (9.3 +/- 3.2 and 6.6 +/- 2.7; p < 0.001), at 25 W (20.6 +/- 4.8 and 14.1 +/- 5; p < 0.001) and at 50 W (25.9 +/- 5.4 and 17.3 +/- 5.8; p < 0.001). The increase in mean mitral gradient from the baseline to 50 watts was 16.7 +/- 4.5 mmHg in group I, which was greater than in group II and III (11.1 +/- 4.1 and 6.8 +/- 2.6 mmHg; p < 0.001).

CONCLUSIONS

Exercise Doppler echocardiography enabled us to define a differential hemodynamic profile in patients with severe mitral stenosis which can be used in isolation as an indicator of severity in this condition.