Echo Doppler Parameters of Diastolic Function

Doppler Mitral Flow Velocity Patterns

Doppler measurement of the mitral flow velocity provides unique information about the velocity of blood flow across the mitral valve into the ventricle during diastole. This velocity is a complex function of the pressure gradient across the mitral valve, defined by the law of conservation of energy equation. Hence, flow velocity represents the intermediate link between hemodynamic conditions indicated by instantaneous left atrial and left ventricular pressures and the filling characteristics of the ventricle.

Mitral flow velocity variables are recorded from the apical four-chamber (A4C) view with pulsed-wave (PW) Doppler by placing a 1- to 2-mm sample volume between the mitral leaflet tips at their narrowest point, which is visualized with two-dimensional echocardiography (2DE) at end-expiration during normal breathing. The Doppler gain and filter settings should be as low as possible, with sweep speed at 50 to 100 mm/s and the spectral Doppler baseline one-third to halfway up on the monitor display. Variables that can be measured include peak mitral flow velocity in early diastole (E wave) and during atrial contraction (A wave), mitral E wave deceleration time (DT), the E wave velocity just before atrial contraction (E at A), the duration of mitral A wave velocity (Adur) (sample volume at the mitral annulus level), and isovolumic relaxation time (IVRT). In young, healthy individuals, there is a rapid acceleration of blood flow from the left atrium (LA) to the left ventricle (LV) after mitral valve opening.

• E wave: Early peak filling velocity of 0.6 to 0.8 m/s occurs 90 to 110 ms after the onset of mitral valve opening. This E wave occurs simultaneously with the maximum pressure gradient between the LA and LV that in turn depends on the pressure difference along the flow stream, LV relaxation, and the relative compliance of the two chambers. The normal E wave pattern shows rapid acceleration and deceleration; normal deceleration slope is 4.3 to 6.7 m/s. Mitral DT, as defined by the time interval from the peak E wave to its extrapolation to baseline, typically ranges from 150 to 240 ms (normal values range from 160–200 ms).

• E wave deceleration time (DT): DT is prolonged in patients with LV relaxation abnormalities because it takes longer for LA and LV pressure to equilibrate. A low normal DT, on the other hand, can be seen in normal young subjects, in whom there is vigorous LV relaxation and elastic recoil, and a short DT if there is a decrease in LV compliance or marked increase in LA pressure as in advanced diastolic dysfunction (DT <150 ms).

• Diastasis: Early diastolic filling is then followed by a variable period of minimal flow (diastasis). The duration of diastasis is dependent on heart rate; it is longer with slow heart rates and entirely absent with faster rates.

• A wave: Last, the A wave, which is the result of an atrial contraction (“atrial kick”) pushing the remaining blood from the LA to the LV, follows the diastasis and is influenced by LV compliance and LA contractility ( Fig. 35.1 ). The normal A wave velocity typically is significantly smaller than the E wave.

  

• E/A ratio: In young, healthy individuals, the E/A ratio is greater than 1. Sinus tachycardia, premature atrial contraction, and first-degree atrioventricular block may result in fusion of the E and A waves. The peak A wave velocity in fused E and A velocity, with an E-at-A wave velocity greater than 20 cm/s is larger than it would have been at a slower heart rate, when mitral flow velocity has time to decrease before atrial contraction. In these cases, the E/A wave ratio may be reduced compared with values obtained at a slower heart rate, so that more reliance on other Doppler variables is needed when interpreting the fused LV filling pattern.

• With aging, the LV relaxation takes longer, primarily because there is a gradual increase in systolic blood pressure and LV mass, resulting in reduced LV filling in early diastole and increased filling at atrial contraction. The peak E and A wave velocities become approximately equal during the sixth and seventh decade of life. DT and IVRT become longer with age, and atrial contraction contributes up to 35% to 40% (as opposed to 10%–15% in adolescents) of LV diastolic stroke volume. With progressively worsening diastolic function, transmitral flow evolves in a recognizable pattern.

• Grade 1 diastolic dysfunction (abnormal relaxation): There is a low E wave (<50 cm/s) and a high A wave, resulting in an E/A ratio less than 1. DT is prolonged and is usually longer than 240 ms, and IVRT, the earliest Doppler manifestation of diastolic dysfunction (measured by PW or continuous-wave [CW] Doppler), is longer than 110 ms. Often considered the transition from grade 1a to grade 1b, abnormal relaxation is followed by a decrease in late LV compliance, resulting in a rise in LV end-diastolic pressure (LVEDP). This rise in end-diastolic pressures truncates atrial systole causing a shortened duration of the mitral A wave with a more rapid (i.e., shorter) A wave deceleration time. In fact, an A-wave deceleration time 60 ms or less predicts an LVEDP greater than 18 mm Hg.

• Grade 2 diastolic dysfunction (pseudonormalization): This occurs when there is a rise in mean left atrial pressure and a decrease in early and late compliance of the left ventricle (LV). It is associated with a normal appearance of the transmitral inflow (“pseudonormal” pattern) with an E/A ratio between 0.8 and 2.0 and a DT between 150 and 200 ms.

• Grade 3 diastolic dysfunction (restrictive filling): With disease progression, grade 3 diastolic dysfunction or restrictive filling develops. There are a very high E wave, a low A wave, and a significantly decreased DT. The E/A ratio is typically greater than 2, and the DT is less than 150 ms. In previous iterations, restrictive filling pressures were subcategorized to either reversible grade 3 or fixed restrictive pattern (grade 4) depending on the response to the Valsalva maneuver or other preload reducing maneuvers. This categorization has since been removed from the current 2016 ASE/EACVI joint recommendations for the assessment of LC diastolic function. Doppler criteria used to define grades of diastolic dysfunction are summarized in Table 35.1 .

  TABLE 35.1

  Doppler Parameters in Normal Population and Various Grades of Diastolic Dysfunction.

  Criteria	Normal Young	Normal Adult	Impaired Relaxation (Grade 1)	Pseudonormal (Grade 2)	Restrictive (Grade 3)
  E/A ratio	≥0.8	≥0.8	≤0.8 + E <50 ms	0.8–2.0 (reverses with Valsalva maneuver)	>2.0
  Deceleration time (ms)	<240	150–240	≥240	150–200	<150
  IVRT (ms)	70–90	70–90	>90	<90	<70
  PV S/D ratio	<1	≥1	≥1	<1	<1
  PV AR-MV A wave duration (ms)	≥30	≤0	≤0 or ≥30	≥30	≥30
  AR velocity (cm/s)	<35	<35	<35	≥35	≥35
  Propagation velocity (cm/s)	>55	>55	>45	<45	<45
  Mitral e′ velocity (cm/s)	>10	>8	<8	<8	<8
  Mitral E/e′	<10	<10	>10	>10	>10
  TR velocity (m/s)	<2.8	<2.8	>2.8	>2.8	>2.8s
  PASP (mm Hg)	<25	<36	>36	>36	>36

  AR , Atrial regurgitation; E/A , Doppler ratio of early to late transmitral flow velocity; IVRT , isovolumetric relaxation time; MV , mitral valve; PASP, pulmonary artery systolic pressure; PV , pressure volume; S/D , systolic velocity/diastolic velocity; TR, tricuspid regurgitation.

• Mid-diastolic (L) wave: The Doppler imaging of mitral inflow may have additional forward flow during mid-diastole. The prominent mid-diastolic filling “hump” has been described as a mitral L-wave. The L-wave is often seen in patients with a markedly prolonged LV relaxation or with elevated LV filling pressures, though it can be seen in healthy individuals with bradycardia.

Valsalva Maneuver

Because diastolic function is affected by preload change, the Valsalva maneuver is a test used to modify cardiac loading condition, which is helpful in the measurement of mitral inflow parameters. The Valsalva maneuver is performed by forceful attempted expiration (∼40 mm Hg) against a closed glottis, resulting in a complex hemodynamic process involving four phases. During the strain phase of the maneuver, preload (mean LA pressure) is reduced, and peak mitral E wave velocity decreases by at least 20%. There is also a simultaneous, albeit smaller, decrease in peak A wave velocity during the strain phase as well. With pseudonormal mitral flow patterns, the Valsalva strain lowers the elevated LA pressure and reveals the underlying impaired LV relaxation, resulting in a measured E/A ratio below 1. Patients with restrictive filling patterns or individuals who have a sensitivity to preload revert to a pseudonormal or even impaired relaxation pattern. Patients who have restrictive filling patterns and exhibit no change with Valsalva have severe irreversible or fixed diastolic function. The primary limitation of the routine use of the Valsalva maneuver is that it is difficult to obtain adequate tracings. ^, Occasionally, the position of the sample volume may move during the maneuver. In addition, the inherent difficulties in performing an adequate Valsalva maneuver may limit its use in routine practice. In current guidelines, the Valsalva maneuver can be considered an ancillary technique to assess for elevated filling pressures.

Pulmonary Venous Flow

Accurate pulmonary vein (PV) flow velocity can be obtained from the A4C view with PW Doppler in 85% to 90% of patients. The right upper PV is the most frequently visualized and accessible from the transthoracic echocardiographic examination. To properly obtain the PV flow with Doppler, the sample volume should be placed approximately 1 to 2 cm into the pulmonary vein, with the box size adjusted to 3 to 4 mm, Doppler filter set to 200 Hz, and sweep speed adjusted to 50 to 100 mm/s. The flow from the PV to the RA occurs in three phases: antegrade systolic, antegrade diastolic, and retrograde after atrial contraction. The normal pulmonary venous waveforms are quadriphasic, though they area often seen as triphasic. In 70% of patients, it is difficult to discriminate between the two systolic components of the PV flow. However, in patients with low filling pressures, systolic forward flow becomes biphasic, and the PV flow pattern is quadriphasic. The first phase is early systolic (PVs1). It occurs in early systole and represents the increase in pulmonary venous flow secondary to atrial relaxation. The second phase, late systolic (PVs2), occurs in mid to late systole. It is caused by the increase in pulmonary venous pressure propagated through the pulmonary arterial tree from the right side of the heart. The apical systolic annular motion of the mitral annulus is also believed to contribute to this finding. This phase reflects the reservoir function of the LA. The next phase is early diastole (PVd), which occurs during ventricular relaxation and is influenced by LV filling. It corresponds to transmitral E velocity and represents LA conduit function. The last phase is peak reversed flow velocity at atrial contraction (PVa or PV Ar), which occurs in late diastole; is influenced by late diastolic pressures in the LV, atrial preload, and LA contractility ; and reflects the LA booster function ( Fig. 35.2 ). The PVa velocity and duration depend on atrial preload and contractility. Similar to the Valsalva maneuver, PV sampling has consistently ranked among the least feasible parameters but can be used as ancillary information when assessing LV filling pressures.