Doppler jet in mitral stenosis with regurgitation

Doppler jet in mitral stenosis with regurgitation

Doppler jet in mitral stenosis with regurgitation: Mitral Doppler interrogation is usually done from the apical four chamber view. Good colour Doppler jet is initially obtained and the Doppler cursor is then aligned parallel to it. Continuous wave is used as the velocity is much above the aliasing limit of pulsed Doppler. Since the mitral antegrade flow is towards the apex, the diastolic jet of mitral stenosis is displayed above the base line. Regurgitant jet into left atrium, being away from the apex, is displayed below the baseline.

Mitral valve area can be calculated from the pressure half time (PHT) of the initial downward slope of the mitral A wave, which fuses with the E wave in mitral stenosis. Lower the slope, lower the mitral valve area and higher the severity of mitral stenosis. Pressure half time is the time taken for the gradient to reduce to half of its peak value. PHT 220 ms corresponds to a mitral valve area of 1 square centimeter. Here the PHT is 107 ms, hence mitral valve area will be higher (machine calculated value displayed as 2 square centimeters).

Mitral valve area by pressure half time: 220/PHT

Mitral valve area calculated by PHT has its own limitations, especially in the immediate post balloon valvotomy situation where there is an abrupt hemodynamic change [1]. Error increases if there is significant mitral regurgitation.

Peak and mean mitral diastolic gradient is estimated by tracing out the outline of the mitral diastolic flow. In this case, though the mitral valve area by pressure half time is good (2.0 sq. cm), the mitral gradient is a bit high because of enhanced flow due to mitral regurgitation and the shortened diastole as a result of relatively fast heart rate (97/min). This is why beta blockers are used to lower heart rate and thereby the gradient in mitral stenosis. Lowering of gradient leads to lower left atrial and pulmonary venous pressure. This in turn reduces pulmonary congestion and exertional dyspnea.

The intensity of mitral regurgitation (MR) jet indicates a mild to moderate mitral regurgitation. But the intensity of the jet can be lower if the cursor is not well aligned with an eccentric MR jet. Hence there is always a chance of underestimation of severity in an eccentric MR jet.

Reference

1. Wisenbaugh T, Berk M, Essop R, Middlemost S, Sareli P. Effect of mitral regurgitation and volume loading on pressure half-time before and after balloon valvotomy in mitral stenosis. Am J Cardiol. 1991 Jan 15;67(2):162-8.