Validation of continuous-wave Doppler measurements of mitral valve gradients during exercise — a simultaneous Doppler-catheter study

In patients with mitral stenosis, continuous-wave Doppler measurements of the maximal transmitral inflow velocity can be converted into transvalvular pressure gradients using the modified Bernoulli equation. Because of close correlations between Doppler- and catheter-measured gradients this method has become a valuable tool in non-invasive evaluation of mitral stenosis at rest. However, in some patients, exercise studies are necessary to determine the haemodynamic significance of the valve stenosis. The accuracy of continuous-wave Doppler in this setting has not yet been validated. Thus, in 20 selected patients with pure or predominant mitral stenosis, continuous-wave Doppler echo-cardiography was performed during left- and right-heart catheterization. At rest and during submaximal bicycle exercise, Doppler and pressure measurements were simultaneously performed. The Doppler gradient was calculated according to the modified Bernoulli equation while the mean manometric gradient was determined from the simultaneous pulmonary wedge and left ventricular pressure curves. Exercise caused a significant increase of cardiac output (4·8+ 1·3 to 5·7±1·31 min−1) and heart rate (59·7±12·0 to 95·3±14·3 beats minmin−1). The mean Doppler gradient increased from 6·8 ± 2·1 to 12·2 ± 3·2 mmHg. The manometric gradient showed a comparable increase of 9·5 ± 2·4 to 17·2 ± 3·7 mmHg, respectively. Correlation between Doppler and manometric data was close (y = 0·79x − 0·67,r = 0·90, SEE= 0·97 mmHg) at rest and still good during exercise (y = 0·71x − 0·10, r = 0·82, SEE= 1·97 mmHg). Thus, in some patients with borderline resting gradients and valve areas, exercise Doppler might allow further identification of the haemodynamic severity of mitral stenosis.