Abstract 771: Noninvasive Assessment of Regional Ventricular Function Using Vector Velocity-Based Strain Analysis
Background: We studied regional ventricular function in an open-chest pig model using vector velocity imaging (VVI) guided ultrasound strain and strain rate analysis.
Methods: 9 anesthetized open-chest piglets (3–6.5 kg), heart rate 60–100 bpm underwent RV/LV pacing at 130 bpm inducing regional ventricular wall stress. Serial changes of strain and strain rate during pacing were measured in the endocardial posterior/lateral and septal area. Imaging was performed with an Acuson Sequoia ultrasound system and a 15L8 probe (14 MHz) in short axis transverse basal and oblique apical views. All data were analyzed offline using VVI v30 (Siemens) software.
Results: There was a consistent significant difference (p <0.04) between the subendocardial septum (strain m 8.14° ± 3.45 and strain rate m 0.82°/sec ± 0.23) and the opposing posterior/lateral region (strain m 4.12° ± 2.53 and strain rate m 0.62°/sec ± 0.37). RV/LV pacing resulted in a decrease of peak systolic strain from m 7.68 ± 4.35 to m 6.59 ± 3.23 in the septal myocardium. At baseline, earlier contraction and higher strain and strain rate were found in the endocardium suggesting LV strain and motion originates in the innermost layer with decreasing amplitude through the myocardial wall.
Conclusion: Our study showed highest strain rate in the subendocardium at the septal level with lower mid myocardial values. Pacing altered regional dynamics and also disturbed the sub-endo to myocardial gradient in the septum.