Transmitral Doppler tracing from apical four chamber view showing varying degrees of fusion of mitral E and A waves. E/A reversal is also evident in the later three beats due to partial E/A fusion.
Mitral E-A fusion
Transmitral Doppler shows an early diastolic E wave and an atrial systolic A wave, normally separated by a short interval in diastasis where there is no pressure gradient across the mitral valve when the normal valve is widely open. Tachycardia shortens the period of diastasis and leads to E-A fusion. E-A fusion is also seen in mitral stenosis when there is no diastasis due to persistently elevated left atrial pressure causing a continuous transmitral gradient. First degree atrioventricular block also enhances the possibility of E-A fusion.1,2
Assessment of diastolic function in mitral E-A fusion
When the mitral E-A fusion is partial as in the latter three beats of the picture shown above, it is still possible to measure peak E and A velocities and demonstrate E/A reversal suggesting left ventricular diastolic dysfunction. But when there is complete E-A fusion as in the first two beats of the illustrated image, it is not possible to calculate the E/A ratio to assess diastolic function. Sohn DW and colleagues suggested using mitral annular velocity measured by tissue Doppler in such cases to assess left ventricular diastolic function.3 They showed that there is a good correlation of the ratio between peak fused mitral inflow velocity and peak fused mitral annular velocity with left ventricular filling pressure. They mention that a ratio of 8 more predicts left ventricular filling pressure of fifteen millimeters of mercury or more, with a fair sensitivity of sixty five percent and specificity of seventy four percent.
Agmon Y, Freeman WK, Oh JK, Seward JB. Diastolic mitral regurgitation. Circulation. 1999 Jun 1;99(21):e13.
Nagueh SF, Appleton CP, Gillebert TC, Marino PN, Oh JK, Smiseth OA, Waggoner AD, Flachskampf FA, Pellikka PA, Evangelisa A. Recommendations for the evaluation of left ventricular diastolic function by echocardiography. Eur J Echocardiogr. 2009 Mar;10(2):165-93.