Guidelines for the Echocardiographic Assessment of the Right Heart ...

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700 Rudski et al Journal of the American Society of Echocardiography
July 2010
Figure 13 Doppler echocardiographic determination of pulmonary
artery (PA) diastolic pressure (PADP) and mean PA
pressure by continuous-wave Doppler signal of pulmonic
regurgitation. Point 1 denotes the maximal PI velocity at the beginning
of diastole. Mean PA pressure correlates with 4 (early
PI velocity) 2 + estimated RAP, in this example 37 mm Hg + RAP.
Point 2 marks the PI velocity at end-diastole. PADP is correlated
with 4 (end PI velocity) 2 + estimated RAP. In this example,
PADP is 21 mm Hg + RAP.
basis of the fundamental equation of flow (F = DP/R), the abnormal
exercise-induced increase in pressure can be ascribed to supranormal
cardiac output (eg, in athletes) or to a normal increase in flow but
a rise in resistance due to limited capability of the pulmonary vascular
bed (eg, in chronic obstructive pulmonary disease or congenital heart
disease). In this setting, the ratio of Dpressure (estimated by TR velocity)
to flow (estimated by the RVOT time-velocity integral) may be
helpful to distinguish whether the increased pressure is related to
an increase in flow or in resistance. 96
Recommendation: In patients with dyspnea of unknown
etiology, with normal resting echocardiographic results
and no evidence of coronary artery disease, it is reasonable
to perform stress echocardiography to assess stress-induced
PH. This technique should be considered as well in subjects
with conditions associated with PA hypertension. Supine
bicycle exercise is the preferred method for SPAP measurement.
An upper limit of 43 mm Hg should be used in patients
at nonextreme workloads. In subjects with valvular
heart disease, the American College of Cardiology and
American Heart Association cutoffs should be used to
help guide management.
NONVOLUMETRIC ASSESSMENT OF RIGHT VENTRICULAR
FUNCTION
Determination of RV systolic function is similar to that of the left ventricle,
albeit more challenging. The right ventricle has superficial circumferential
muscle fibers responsible for its inward bellows
movement, as well as inner longitudinal fibers that result in the
base-to-apex contraction. 20 Compared with the left ventricle, the
base-to-apex shortening assumes a greater role in RV emptying.
Global assessment of RV function includes the myocardial performance
index (MPI), RV dP/dt, RV EF, and FAC (see above). Regional
approaches include tissue Doppler–derived and 2D strain, Dopplerderived
systolic velocities of the annulus (S 0 ), and TAPSE. Each
method is affected by the same limitations from the corresponding
left-sided techniques. The RV EF may not represent RV contractility
in the setting of significant TR, just as the LV EF is limited by mitral regurgitation.
For S 0 and TAPSE, the regional velocities or displacement
of the myocardium in a single segment may not truly represent the
function of the entire right ventricle. Regional strain measurements
are plagued by the same issues, as well as that of poor reproducibility.
There is a lack of outcomes data relating to quantification of RV systolic
function. Nonetheless, each of the methods is described below,
reference values are displayed, and recommendations for measurements
are proposed.
A. Global Assessment of RV Systolic Function
RV dP/dt. The rate of pressure rise in the ventricles (dP/dt) is an
invasive measurement developed and validated as an index of
ventricular contractility or systolic function. It was initially described
by Gleason and Braunwald 97 in 1962 in both the left
and right ventricles.
Although less studied and more sparsely used than for the left ventricle,
RV dP/dt can also be accurately estimated from the ascending
limb of the TR continuous-wave Doppler signal. 98,99 RV dP/dt is
commonly calculated by measuring the time required for the TR jet
to increase in velocity from 1 to 2 m/s. Using the simplified
Bernoulli equation, this represents a 12 mm Hg increase in
pressure. The dP/dt is therefore calculated as 12 mm Hg divided by
this time (in seconds), yielding a value in millimeters of mercury per
second. Although the time from 1 to 2 m/s is most commonly
used, the best correlation between echocardiographic and invasive
measures was found by using the time for the TR velocity to
increase from 0.5 to 2 m/s. 99 In this case, the numerator for the calculation
is 15 mm Hg, representing the pressure difference as calculated
from the simplified Bernoulli equation between 2 and 0.5 m/s.
Advantages: This is a simple technique with a sound physiologic
basis.
Disadvantages: There are limited data in both normal subjects
and pathologic conditions. RV dp/dt is load dependent. RVdp/dt
will be less accurate in severe TR because of neglect of the inertial
component of the Bernoulli equation and the rise in RA pressure.
Recommendations: Because of the lack of data in normal
subjects, RV dP/dt cannot be recommended for routine
uses. It can be considered in subjects with suspected RV
dysfunction. RV dP/dt < approximately 400 mm Hg/s is
likely abnormal.
RIMP. The MPI, also known as the RIMP or Tei index, is a global estimate
of both systolic and diastolic function of the right ventricle. It is
based on the relationship between ejection and nonejection work of