Speckle-tracking strain analysis:
Speckle tracking strain echocardiography was used to determine RV
lateral free wall average peak systolic strain . RV strain was measured
using ECHOINSIGHT software (version 2.2.6.2230, Epsilon Imaging, Ann
Arbor, MI). Based on the 4-chamber apical view, three successive RV
cardiac cycles with a frame rate of 70-120/s were recorded. Right
ventricular endocardial border was manually traced in still end-systolic
frames, and the software performed automated tracking throughout the
cardiac cycle. The automated tracking was visually verified and manually
adjusted for adequate border delineation. Tissue velocities in the 2D
plane are displayed throughout the cardiac cycle, representing magnitude
and direction of motion. Finally, strain data was generated by analyzing
the speckle pattern along the endocardial border in reference to one
another. Longitudinal strain is defined as the percentage shortening of
a regional area of interest (ROI) relative to its original length and is
expressed as a negative value. The software further categorized the RV
myocardium into six sections: basal RV free wall, mid-RV free wall,
apical free wall, left basal septum, mid-left septum, and left apical
septum and calculated the regional wall strain with the same manner. RV
lateral free wall strain (average of the basal, mid, and apical free
wall) was used in our analysis. Figure 1 demonstrated a
representative case of RV dimension measurement.