“ECHO EVALUATION OF DIASTOLIC FUNCTION:
IS THERE A BETTER WAY”
DIASTOLIC DYSFUNCTION PANEL
Wanda M. Popescu, MD
The three main objectives of this lecture are for the participant to understand:
1. Echocardiographic methods used to detect intraoperative diastolic
dysfunction
Diastolic physiology
Traditionally, from a clinical stand point of view, the cardiac cycle is divided into
systole and diastole. Systole, comprised of isovolumic contraction and ejection,
commences with the closure of the atrioventricular valves and finishes with the
closure of the semilunar valves, which marks the start of diastole. The diastolic
component of the cardiac cycle is comprised of four phases: isovolumic relaxation,
rapid filling, diastasis, and atrial contraction. The sequences of events that occur in
the left ventricle (LV) during diastole are described below and depicted in Figure 1.
1. Isovolumic contraction starts with the closure of the aortic valve (AV). Due
to ventricular relaxation, the pressure in the LV declines rapidly to levels
below the left atrial pressure (LAP) and promotes opening of the mitral
valve (MV).
2. Rapid filling phase is responsible for approximately 80% of the LV filling.
Due to the continuous myocardial relaxation as well as to the elastic
recoil properties of the myocardium, the LV pressure continues to drop
(in spite of a LV volume increase) therefore creating a suction effect and
promoting forward flow from the pulmonary veins via the left atrium into
the LV.
3. Diastasis is characterized by the equilibration of LAP and LVP. At this time
point, filling is minimal and is based on the passive compliance of the LV.
4. Atrial contraction results in an increase in LAP, which promotes forward
flow into the LV as well as retrograde flow into the pulmonary veins.
Therefore, the contribution of this phase to the total stroke volume
(usually 20-25%) is dependent upon ventricular compliance and atrial
contractility. At this time point, any LV volume increase is coupled with
an LVP increase. The increasing LVP eventually exceeds that of the LAP
and promotes closure of the MV.
From a physiologic point of view, based on the load-barring characteristics of the
myocardium, the cardiac cycle is divided into three phases: systolic contraction,
relaxation and diastolic filling. The systolic contraction comprises the isovolumic
contraction and the first half of ejection. This phase is characterized by an increase
in the LVP followed by myocardial fiber shortening, ultimately resulting in ejection
of blood into the ascending aorta. After the initial ejection the myocardial fiber
transitions towards the relaxation phase, which consists of the second half of
ejection, isovolumic relaxation and the rapid filling phase. The diastolic filling phase
is the period in which the LV fills with blood from the LA and includes the rapid
filling phase, diastasis and atrial contraction. This approach to the division of the
cardiac cycle illustrates the interdependency of systole and diastole.
The two main determinants of ventricular filling are ventricular relaxation and
compliance. Ventricular relaxation is the process by which the myocardial fiber
returns to its initial length and force. Relaxation can be defined as the rate and
duration of LVP decline, which occurs after contraction. The traditional method of
LV relaxation assessment consists of measuring the rate of decay in LVP during
isovolumic relaxation. This assessment is performed invasively, with high fidelity
manometers. As such, one index of ventricular relaxation is the –dP/dT, which
represents the minimum value of the first derivative of LVP with respect to time. A
more frequently used index of relaxation is tau, which is the time constant of
isovolumic relaxation. A prolongation of tau is usually consistent with impaired
relaxation. LV compliance is defined as the change in volume in respect to the
change in pressure (V/P), which occurs during diastolic filling. However, the
overall ventricular filling is also impacted by other factors such as: diastolic suction
effect, viscoelastic forces, pericardial restraint, ventricular interdependency, atrial
contractility, MV dynamics, intrathoracic pressures, heart rate and rhythm as well as
loading factors.
Echocardiographic indices used for diastolic function assessment
Doppler echocardiography has become the gold standard non-invasive,
comprehensive and reliable diastolic function assessment tool. As a general
principle, the diastolic function assessment should be part of a systematic and
comprehensive examination, which should include the evaluation of the systolic
function of the heart. A complete perioperative TEE evaluation of diastolic function
includes a combination of Doppler techniques: pulsed wave Doppler (transmitral
flow and pulmonary vein flow), Doppler tissue imaging and transmitral color Mmode. In order to obtain adequate Doppler flow profiles, an important technical
aspect is represented by aligning the Doppler beam as parallel as possible with the
path of blood flow (any angle other than 0 will underestimate the true velocity of
blood). The TEE views routinely employed for a parallel alignment with blood flow
are the mid-esophageal 4-chamber view (ME 4 Ch) and the mid-esophageal long
axis view (ME LAX). All measurements are made during a period of hemodynamic
stability and during apnea (ventilator off). In patients with significant mitral valve
disease or who have had mitral valve surgeries assessment of the diastolic function
is impossible. Similarly, in patients who are in rhythms other than sinus assessment
of diastolic function by Doppler techniques is less reliable.
The normal and pathological values of the Doppler indices described below are
presented in Table 1. It must be observed that these values are mostly derived from
studies performed on awake patients, breathing spontaneously. However, presently
we do not have sufficient information to present different cut-off values for the
anesthetized patients. At the same time, normal aging influences these values to
some extent.
1. Left ventricular inflow velocities (TMF) and Pulmonary vein flow velocities (PVF)
TMF Technique: a CFD sector is placed across the LV inflow to detect the direction
of blood flow for better alignment; a PWD sample is placed at the tips of the MV
leaflets
The spectral display in TEE imaging consists of 2 negative waves: E & A
Parameters: Early filling peak velocity (E) represents the rapid filling phase. It
depends on the pressure gradient across the MV. The deceleration time (DT) of the
E wave velocity represents the amount of time required for the peak of the E wave
to reach baseline. DT correlates with the time required for LAP and LVP to equalize
and it is a measure of LV compliance. The late filling peak velocity (A) reflects the
atrial contraction. The more common index used is the E/A ratio. The A duration
(Adur) is the interval from the beginning to the end of the A wave and represents a
measure of LVP. The Adur is measured by moving the Doppler sample to the level of
the mitral annulus. The isovolumic relaxation time (IVRT) is the time interval
between the closure of the AV and the opening of the MV and represents mainly an
index of LV relaxation. It can be determined by placing a CWD beam midway
between LV outflow and inflow in the deep transgastric view or the transgastric
long axis view. Due to their dependency on pressure gradients, all the above indices
appear to be load dependent.
PVF Technique: a PWD sample is placed 1 cm into the left upper pulmonary vein
The spectral display in TEE imaging consists of 2 positive waves (S, D) and a
negative wave (a)
Parameters: Peak systolic flow velocity (S) represents the flow velocity of blood
from the pulmonary vein into the LA during LV systolic contraction. Occasionally
this wave is biphasic (S1 & S2), which represents the atrial relaxation (S1) and the
mitral annular descent (S2). Peak diastolic flow velocity (D) represents the
velocity of blood flow during LV diastole. This wave coincides with, has a similar
contour and depends on the same factors as the E wave of the LV inflow. The more
commonly used index is the S/D ratio. The pulmonary vein flow reversal in late
diastole (a) occurs due to the atrial contraction and is dependant upon atrial
contractility and LVP. Another index used is the “a duration” (adur). Similarly to the
LV inflow indices, the PVF parameters are significantly load dependent.
2. Mitral Annular Doppler Tissue Imaging (DTI)
This technique assesses diastolic function by evaluating the intramyocardial
velocities at the level of the mitral annulus. The myocardial motion produces high
amplitude and low velocity signals.
Technique: DTI sample at the level of the mitral annulus both, on the lateral and
septal walls
The spectral display in TEE imaging consists of a negative wave (S’) and 2 positive
waves (E’ and A’)
Parameters: The S’ is caused by the descent of the mitral annulus during LV systole
and represents primarily an index of systolic function. The E’ represents the
myocardial elongation which occurs during early diastole and is directly dependent
upon the rate of relaxation. The E’ has an excellent correlation with the relaxation
indices measured during cardiac catheterization. The A’ represents the myocardial
distension generated by the blood flow during atrial contraction. In healthy
individuals, the E’ and A’ spectral display mirrors the pattern of the E and A wave
display of the LV inflow. An index utilized to assess LV filling pressures is the E/E’
ration. The lateral wall will have higher velocity values than the septal wall due to
an increased freedom of movement. However, if wall motion abnormalities are
present (i.e. ischemia) it is important to average the E’ lateral and septal velocities
(E’avg). The DTI derived indices used for diastolic function assessment appear to be
less sensitive to loading conditions, in particular in patients with known systolic or
diastolic dysfunction.
3. Color M-mode: Propagation velocity (Vp)
This technique evaluates the propagation of blood from the mitral annulus to the LV
apex in early diastole. The Vp is similar to a multitude of simultaneous PWD
interrogation signals placed from the MV orifice to the apex.
Technique: a narrow CFD sector id placed over the LA, MV and LV. The M-mode
cursor is placed through the center of the MV inflow. To measure the Vp , a slope
should be drawn from the MV at the first aliasing velocity during early filling to 4 cm
distally to the LV apex. Healthy patients have a Vp > 55 cm/sec. A slope < 45 cm/sec
suggests diastolic function impairment. The load dependency of this index is
questionable, with many studies showing contradictory results.
Diastolic pathophysiology and echocardiographic grading of diastolic
dysfunction
The initial manifestation of diastolic dysfunction consists of an abnormal relaxation.
The ventricle requires a longer period of time to relax, and thus, the LVP decay
occurs at a lower rate. As a consequence, the pressure gradient across the MV is
lower than normal and the ventricle fills less during the rapid filling phase with an
increased contribution to the stroke volume of the atrial contraction phase. Normal
left atrial pressures and no abnormality in ventricular compliance characterizes this
period. This stage is consistent with Grade I diastolic dysfunction or “impaired
relaxation”.
Echocardiographic indices:
Due to a decreased pressure gradient across the MV, the E wave of the LV inflow will
have a lower velocity while the A wave will have a compensatory increased velocity.
As such, the E/A is less than 0.8. As the ventricle requires a longer period of time to
fully relax, the DT and IVRT will be prolonged. The PVF will still maintain an S/D >1
as the LAP is normal. Due to the impaired relaxation, the DTI of the mitral annulus
will demonstrate a decreased E’ velocity.
As the disease progresses the LV compliance decreases. Hence the rate of LVP decay
in diastole is even less and therefore, the pressure gradient across the MV decreases
further. In order to normalize this pressure gradient, as a compensatory mechanism,
the LAP increases and improves flow from the LA to the LV in the rapid filling phase.
This stage is consistent with Grade II diastolic dysfunction or
“pseuodonormalization”.
Echocardiographic indices:
The increase in LAP and restoration of a normal pressure gradient across the MV
determines a “pseudonormal” pattern on the LV inflow spectral display. However,
the increases in LAP results in less forward flow from the pulmonary veins into the
LA during LV systole and an increase in retrograde flow into the pulmonary veins
during atrial contraction. As such, the PVF spectral display changes into a S/D < 1
while the adur is prolonged as compared to normal. The decreased LV compliance
leads to a decreased velocity of the E’ on the DTI spectral display. At this point, the
spectral display of the DTI does not “pseudonormalizes” and does not mirror the
pattern of the LV inflow display.
In late stages of disease, the LV compliance decreases drastically and causes
significant increases of LVP and LAP. The high-pressure gradient across the MV
results in a fast acceleration of blood in the LV during the rapid filling phase. The
noncompliant ventricle determines an immediate rise in LVP and allows a small
amount of blood to enter the cavity. Atrial contraction will produce just a limited
amount of forward flow with the majority of blood flowing retrograde into the
pulmonary veins (low pressure). This stage is consistent with Grade III diastolic
dysfunction or “restrictive filling”.
Echocardiographic indices:
The fast acceleration of blood during the early filling phase and the limited amount
of blood entering the LV during atrial contraction are represented on the LV inflow
display by a high velocity E and low velocity A. As the pressure in the LV and LA
equilibrates fast, the DT is significantly decreased. The PVF display shows a
significantly reduced S wave, with S/D << 1 and an increased a velocity and duration.
The DTI spectral display will depict drastically decreased E’ velocities.
The grading of diastolic function in accordance to the ASE Guidelines for Diastolic
Function Assessment is presented in Figure 2.
Filling Pressure Estimation
In patients undergoing general anesthesia and positive pressure ventilation, the
echocardiographic indices used to assess filling pressures have not been validated.
However, when assessing filling pressure the systolic function of the heart needs to
be accounted for. If the EF is normal, an adur-Adur < 30 or a change in E/A of less
than 0.5 with a Valsalva maneuver implies normal filling pressures. Conversely, a
longer duration of retrograde flow in the pulmonary veins during atrial contraction
(adur-Adur > 30) or a change of more than 0.5 of the E/A with Valsalva implies high
filling pressures. In patients with depressed LVEF, the S/D can be used in addition to
the previously mentioned adur-Adur and E/A values, to differentiate among
patients with normal versus high filling pressures. Regardless of LVEF, E/E’ < 8 is
associated with normal filling pressures while E/E’ > 15 is associated with increased
filling pressures.
Conclusion
Assessment of diastolic function should be an integral part of a comprehensive
perioperative echocardiographic evaluation. Diastolic function assessment relies on
the correlation of multiple echocardiographic indices, interpreted in the context of
the hemodynamic conditions at that time. It is important to remember that no one
index can diagnose or exclude the presence of diastolic function. In the future,
newer diagnostic modalities such as strain and speckle tracking may permit us to
better understand and grade diastolic function.
Table 1
Normal
Impaired
Relaxation
PseudoNormal
Restrictive
Filling
1–2
< 0.8
0.8-1.5
≥2
DT (ms)
150–200
> 200
150–200
< 160
IVRT (ms)
60–100
> 100
> 100
< 60
S/D
>1
>1
<1
<1
a (cm/s)
< 35
< 35
> 35
> 35
TMF
E/A
PVF
adur – Adur
< 30
< 30
> 30
> 30
Vp
> 55
< 45
< 45
< 45
E’
> 8(septal)
>10(lateral)
< 8(septal)
< 10(lateral)
< 8(septal)
< 10(lateral)
< 8(septal)
< 10(lateral)
E/E’
< 8(septal)
< 8(lateral)
<8
<8(septal)
<8(lateral)
<8
9-12
(average)
9-12
> 15(septal)
> 12(lateral)
> 13
Avg E/E’
Figure legends
Figure 1. The first part of the graph depicts the time-course of left ventricular
pressure (LVP) and volume (LVV) and left atrial pressure (LAP) during the cardiac
cycle. According to the clinical definitions, the cardiac cycle is divided into the
systolic and diastolic phases with their subdivisions: isovolumic contraction (IVC),
ejection, isovolumic relaxation (IVR), rapid filling (RF), diastasis, atrial kick (LF).
According to the physiological definitions, the cardiac cycle is divided into
contraction, active relaxation and filling phases. Note that the rapid filling phase is
present in both the active relaxation and filling phases. See text for further
explanations. The second part of the graph depicts the graphical representation of
the determinants of intrinsic left ventricular diastolic function in respect to time.
Note that active relaxation starts after peak ejection, in the second half of systole,
and that the viscoelastic properties contribute to recoil during early diastole and to
ventricular compliance during late diastole.
Figure 2. A practical approach to grade diastolic dysfunction
References:
1. Nagueh SF, Appleton CP, Gillebert TC et al. Recommendations for the
evaluation of left ventricular diastolic function by echocardiography. J Am
Soc Echocardiogr 2009;22:107-33