Abstract
Background: Left ventricular (LV) twist appears to play an important role in effective ejection fraction (EF). MRI based tagging methods are limited for tracking right ventricular (RV) free wall motion, especially for the normal thin free wall. We used a new motion analysis program based on tracking speckles in B-mode echo images to study RV motion. Methods: For our study, 6 small (2-3kg) piglets were intubated and anesthetized; median sternotomy was done to expose the heart. We used a 10MHz sector probe and a 13MHz linear probe to acquire 2D and tissue Doppler images of the RV from the surface of the heart, using liver as a standoff to improve extent and clarity of the RV free wall images. Short axis views were acquired on a GE Vivid 7 Dimension ultrasound system at frame rates >100/sec. The study was conducted at 3 hemodynamic states of baseline and after 10% and 20% volume loading. Data was later analyzed offline in EchoPac using 2D speckle tracking. Results: There was a minimal component of rotation in the free wall of the RV (1°-2°) but more in the septum (5°-8°), which was similar to the rotation of the LV free wall for that level. Strain values were similar in both free wall and the RV side of the septum. With volume loading, there was an increase in the septum (mean 2° ± 1°) amplitude of twist and a decrease in time to peak twist, but the RV free wall showed no significant change. Conclusions: These findings are consistent with observations that the septum plays an important role in RV dynamic function.
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