Abstract 5405: Real Time High-Resolution Dynamic Imaging Provides New Insights for Understanding Cardiac Function
We used high frame rate echocardiography to define the relationship of strain and rotation parameters with dynamic cardiac function. We studied 15 open chest pigs scanned with a 10S probe on a GE Vivid 7 ultrasound system directly from the surface of heart to allow acquisition of high-resolution apical and basal short axis views (>150 frames/sec). Images were analyzed offline in EchoPac PC using a speckle tracking based strain and motion calculation program. We divided the cardiac cycle into 3 phases to describe results. Phase 1 (37% ± 4.5% of RR’ interval; red in figure⇓) ended when septal and global circumferential strain reached peak. After initial clockwise motion, the LV showed counterclockwise rotation and 55% ± 5.5% decrease in short axis area during this phase. Phase 2 (marked blue; 18% ± 3.75% of RR’ interval) ended when lateral wall strain reached peak. Global circumferential strain (1–3% decrease) and short axis area (4–6% increase) showed minimal changes. The septum showed 4–7% decrease and lateral wall showed 3–5% increase in strain. All segments continued to twist and reached peak twist coinciding with peak strain in the LV lateral wall. During Phase 3 (33% ± 2.65% of the RR’ interval; red), all segments showed untwisting, 16–18% reduction in circumferential strain, and 52–59% increase in short axis area. Coordinated and sequential contraction results in LV twisting that continues into very early diastole. The isovolumic phase demonstrates minimal contraction in the lateral wall and relaxation in the septum, resulting in continued early isovolumic twisting (torsion), which is then rapidly released.