What is the role of echocardiography in the diagnosis of cor pulmonale?

Updated: Dec 15, 2017
  • Author: Derek Leong, MD; Chief Editor: Henry H Ooi, MD, MRCPI  more...
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Two-dimensional (2-D) echocardiography usually demonstrates signs of chronic right ventricular (RV) pressure overload. As this overload progresses, increased thickness of the RV wall with paradoxical motion of the interventricular septum during systole occurs. At an advanced stage, RV dilatation occurs, and the septum shows abnormal diastolic flattening. In extreme cases, the septum may actually bulge into the left ventricular (LV) cavity during diastole, resulting in decreased LV diastolic volume and reduction of LV output.

Doppler echocardiography is used to estimate pulmonary arterial pressure, taking advantage of the functional tricuspid insufficiency that is usually present in pulmonary hypertension. This imaging modality is considered the most reliable noninvasive technique to estimate pulmonary artery pressure. However, the efficacy of Doppler echocardiography may be limited by the ability to identify an adequate tricuspid regurgitant jet, which may be further enhanced by using saline contrast. [13]

Several methods exist to assess RV function. One method includes tricuspid annular plane systolic excursion (TAPSE), which is measured by viewing the heart in the apical four-chamber view and using the M-mode function along the lateral tricuspid annulus. By measuring the distance traveled of this reference point during systole, the longitudinal shortening of the RV can be used as a surrogate for global RV function. Limitations include inadequate M-mode placement and the assumption that one segment of RV motion is representative of the entire RV.

Strain, which is distinct from measuring wall-motion abnormalities in traditional echocardiography, involves measuring myocardial deformation to quantitatively assess myocardial function. Two methods currently exist for measuring strain, including tissue Doppler imaging (TDI) and 2-D speckle tracking. TDI uses postprocessing to convert velocity to strain and strain rates, but it is significantly limited by the Doppler angle of incidence. 2-D speckle tracking uses greyscale to detect speckle patterns by tracking natural acoustic markers to calculate velocity vectors with 2-D ultrasonography. However, 2-D speckle tracking relies on high image quality. [14, 15]

Additionally, myocardial performance index (MPI) can also be used to measure RV function by calculating the isovolumetric relaxation time and contraction time divided by the ejection time. Higher MPI indicates greater RV dysfunction, and it is independent of RV chamber size and geometry.

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