Assessment of LV Diastolic Function by Echo in SR and AF

Echocardiographic assessment of left ventricular diastolic function with special reference on diastolic function assessment in atrial fibrillation.
Though there are several parameters for evaluation of left ventricular diastolic function by echocardiography, the most commonly used are the pulsed Doppler mitral E/A ratio and tissue Doppler mitral E/e’ ratio.
Some of the other useful parameters are mitral E velocity deceleration time, changes in mitral inflow with Valsalva maneuver, mitral L velocity, isovolumic relaxation time, left atrial maximum volume index, pulmonary vein systolic/diastolic velocity ratio, color M-mode Vp and E/Vp ratio.
Tricuspid regurgitation jet velocity and pulmonary regurgitation end diastolic velocity indicating pulmonary hypertension are also taken as surrogates of left atrial pressure in the absence of pulmonary disease.
Doppler interrogation of mitral valve is usually done from the apex through the apical four chamber view. The transducer is placed directly over the apex beat and the echo beam is directed upwards.
A good four chamber view of the heart is obtained, showing all four chambers and both atrioventricular valves. The Doppler cursor is then aligned along the long axis of the left ventricle, passing through the mitral valve.
The Doppler sample volume is placed just distal to the mitral valve so that it picks up the flow in the left ventricular inflow. The initial portion of the mitral diastolic flow is called the E wave (early diastolic) and the final portion which occurs during atrial systole is called the A wave.
Normally most of the left ventricular filling occurs during early diastole and the E wave is taller than the A wave. When the ventricular relaxation is impaired in diastolic dysfunction, the atrial contribution to ventricular filling progressively increases and the A wave height increases so that there is equalization of the E and A waves.
As the severity of diastolic dysfunction increases, A wave becomes taller than E wave. This phase is known as E/A reversal. Still further, the E wave becomes taller due to elevated left atrial pressure, mimicking the restrictive filling pattern. This is a type of pseudo normalization of the mitral flow pattern.
The upper half of the image shows the apical four chamber view of the heart. The Doppler cursor and the sample volume are seen along midline of the left ventricle. The lower half of the image shows the Doppler flow pattern across the mitral valve. The x-axis is time and y-axis represent the velocity in cm/s.
A triphasic left ventricular filling pattern with an additional mid diastolic wave, called T wave by some authors and L wave by others, can occur in situations of left ventricular diastolic dysfunction, especially in hypertrophic cardiomyopathy. Another video on this channel describes triphasic mitral flow in more detail.
The normal ratio between the amplitudes of E and A waves (E/A ratio) is 0.75 to 1.5. The mitral flow Doppler patterns in left ventricular diastolic dysfunction has been divided into four stages.
Stage I: In mild diastolic dysfunction, E/A ratio is reversed and < 0.75. The reversal is due to the increase in A wave due to the more forceful atrial contraction to overcome the left ventricular diastolic dysfunction. The deceleration time of the early diastolic filling or DT is normally less than 220 ms. DT is prolonged in diastolic dysfunction. These patients are generally asymptomatic. In stage II diastolic dysfunction, the E wave becomes taller due to elevated left atrial pressure. This is called pseudonormalization of the filling pattern. In this stage E/A reversal can still be demonstrated during Valsalva maneuver. In stage III diastolic dysfunction, the E wave becomes very high so that E/A ratio is more than 1.5 and the DT is below 150 ms. This is also called restrictive filling pattern. In stage IV, this restrictive filling pattern remains fixed even during Valsalva maneuver. Initial stages (I to III) are considered reversible with treatment. Stage IV is considered as advanced. Use of drugs producing bradycardia like beta blockers in stages III and IV may precipitate low output state. Tissue Doppler image with colour kinesis in the inset. E/E’ of the medial mitral annulus is shown as 19.1, indicating type II left ventricular diastolic dysfunction. In diastolic dysfunction, as the relaxation of the ventricle is impaired, the velocity of medial mitral annulus is reduced so that the E/E’ ratio is increased. E wave is measured prior to tissue Doppler imaging and stored so that the software application displays the E/E’ as soon as the E’ is measured. E/E’ below 8 is considered normal while ratio above 15 is considered a feature of left ventricular diastolic dysfunction. E/E’ has been correlated with left atrial pressure as well, which is in fact the left ventricular filling pressure, which increases in left ventricular diastolic dysfunction. Estimation of pulmonary capillary wedge pressure from E/E’ on Tissue Doppler was covered in another video on this channel. The E’ velocity at lateral mitral annulus is different from that at the septal mitral annulus. Septal E’ is slightly lower than lateral E’. E/E’ at lateral mitral annulus more than 10 and E/E’ at septal mitral annulus more than 15 indicates left ventricular diastolic dysfunction. The yellow tracing is pulsed wave tissue Doppler imaging. The next negative wave after E’ occurs during atrial contraction and is designated Aa. The positive wave after Aa is the Sa wave, representing the systolic myocardial wave recorded as the annulus descends towards the apex. E’ velocity is also known as Ea (‘a’ for annulus) velocity or Em (‘m’ for myocardial) velocity. It reflects the early myocardial relaxation and occurs during the ascend of the mitral annulus. Measurement of E’ is useful in differentiation of pseudo normalization in the mitral inflow from the normal pattern. There are also limitations for E/E’ in the assessment of LV diastolic dysfunction. One situation is decompensated advanced systolic heart failure with large left ventricle. Broad QRS with abnormal septal motion, significant mitral regurgitation and presence of cardiac resynchronization therapy are all confounding factors. Usually LV diastolic function assessment by echo relies on mitral inflow velocity measurement with demonstration of E/A reversal as an evidence of diastolic dysfunction. In atrial fibrillation, the absence of atrial contraction and the A wave makes this assessment impossible. Moreover, the variation in the cardiac cycle also causes beat to beat changes in ventricular relaxation. Echo parameters useful in the presence of AF include: Mitral E wave DT and E/E’ Color M-mode derived Vp (early diastolic flow propagation velocity) and E/Vp Peak pulmonary vein diastolic flow velocity Pulmonary vein diastolic wave DT Peak acceleration of the mitral E wave IVRT and ratio of IVRT to the time between onsets of E and e’ wave Flow propagation velocity (Vp) on colour M-Mode, is measured as the slope of the first color aliasing velocity from the mitral annulus in early diastole to 4 cm distally into the left ventricular cavity. A dual Doppler technique has been described, for simultaneous measurement of E and e’ so that the ratio E/e’ can be calculated in the same beat itself. This avoids the beat to beat variation in these values which would compound a non-simultaneous measurement. Short of this novel technique, any measurement in AF would need averaging of values for 5-10 cardiac cycles. Mitral E wave DT < 100 ms correlates with a pulmonary wedge pressure of more than 18 mm Hg. Deceleration time is the duration between the peak of the E wave and the upper deceleration slope extrapolated to the baseline. It is usually measured from the apical four chamber view. Pulmonary vein diastolic wave DT is also measured in a similar way from the right upper pulmonary vein in the apical four chamber view.

References

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