Pulmonary Arterial Hypertension
Figure 1: Complexity of Right Ventricle Contraction Shown on 3D Echocardiography
outflow tract (RVOT), and, if combined with strain rate imaging, could provide a comprehensive assessment of RV volume, contraction and relaxation (see Figure 1). A good correlation between 3D echo and CMR for RV end-systolic and end-diastolic volumes and for RVEF has been shown.25
However, this technique is likely to suffer from the same limitations as MRI scanning. Trabeculation of the right ventricle prevents accurate assessment of end-systolic volumes in particular.26 Furthermore, the reduction in frame rate may render the thin RV free wall relatively difficult to clearly define, especially in patients with substantial wall movement associated with increased HR or CO.
TAPSE is obtained by performing M-mode interrogation of the lateral tricuspid annulus as contraction in the longitudinal plane represents the dominant contribution to RV function. The impact of volume off- loading (tricuspid regurgitation [TR]) is not fully understood.27 has been validated against MRI-assessed RVEF26 and was able to predict prognosis in PAH;28
TAPSE
and in a single study therefore, it has been
included as a prognostic parameter in the ESC/ERS guidelines.
The S-wave of the lateral tricuspid annular velocity profile provides another method of assessing longitudinal free-wall movement.29 study from Meluzin et al.,29
In a 30 control patients had much higher
S-waves (15.5+2.6cm/second) compared with patients with impaired RV function on radionuclide scanning (10.3+2.6cm/second), but the correlation of this parameter with RVEF was less than optimal. An EF of 25% was associated with S-waves ranging from 5.5 to 11.7cm/second.
Note in particular the contribution of right ventricular outflow tract contraction.
30–50% of RV work load is pulsatile, any technique that omits one of these components may fail to correctly determine the implications of changes observed in other parameters. Optimal evaluation of the RV therefore requires instantaneous assessment of RAP, systolic and diastolic PAPs, pulmonary artery distensibility, blood flow acceleration and volumetric changes (absolute volumes and rate of change of volume) through systole and diastole during the same beat.
Current Knowledge of Right Ventricular Changes in Response to Pulmonary Arterial Hypertension
The functional abnormalities of PAH are global RV hypokinesia, paradoxical movement of the interventricular septum associated with the leftward deviation of the interatrial septum, RV dysfunction (increased end-diastolic volume, increased end-systolic volume, increased mass, reduced ejection fraction [EF], reduced cardiac index, reduced stroke volume), pulmonary and tricuspid insufficiency, reduced flow velocity in the pulmonary artery and decreased systolic right coronary artery blood flow.
Despite the large number of observable changes on echocardiography, only Tei index,22
TAPSE, pericardial effusion23,24 and RA23 shown to be independent predictors of outcome.
Assessing Right Ventricular Systolic Function Realtime 3D echocardiography has the potential to provide correct volumetric analysis and prevent exclusion of the contribution of the RV
40 area have been
Assessing Right Ventricular Diastolic Function The tricuspid free-wall isovolumetric relaxation time (IVRT), tricuspid lateral annular early diastolic velocity (E’) and tricuspid lateral annular IVRT differed significantly between the overweight and control children.35
As with the current controversy over the prevalence of EUROPEAN CARDIOLOGY
The Myocardial Performance Index (MPI) was developed by Tei, and relies on the concept that as function deteriorates, the proportion of systole occupied by isometric contraction and relaxation increases.30 In normal people this is
Tissue Doppler-based assessments and could lead to increased utility of
Limitations include direction dependency and the need for frame-by- frame quality assurance; therefore, this technique remains a research tool in patients with pulmonary hypertension.
Speckle Tracking and Vector Velocity Imaging Global peak systolic strain may help detect RV dysfunction when conventional echo is normal.34
this measurement. Doppler strain and strain rate are more sensitive than tissue Doppler imaging and conventional echo. It has been suggested that apical contraction is compromised early using strain- rate imaging in patients with PAH. Strain-rate imaging overcomes the issue of peristaltic contraction that may influence global assessments.15,32,33
The thin wall of the right ventricle may
render post-processing important as adjacent extracardiac stationary speckles may also be tracked (see Figure 2). The analysis of vector velocity data in each region could provide detailed information on regional changes in RV function early in the development of pulmonary hypertension (see Figure 3). Only one study in PAH using vector velocity imaging has been published to date.15
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