Abstract 528: Digital Analysis of High Frame Rate 2D Echocardiography Image Loops Provide New Insights Into Strain Twist Interaction and Heart Function
Background: Cardiac motion is a dynamic interaction of linear and rotational deformation.
Methods: Seven adult pigs underwent midline sternotomy to allow acquisition of very high frame rate images directly from the heart surface. Left ventricular (LV) pressure volume curves were obtained by Millar conductance catheters and apical short axis views acquired with a 10S probe on a Vivid 7 Dimension ultrasound system at >120 fps. After baseline image acquisition, pigs were subjected to escalating doses of dobutamine and then esmolol. Images for each state were obtained and exported to EchoPac PC for offline analysis using 2D speckle tracking.
Results: At baseline, there was a consistent delay of 10 –12% in R-R′ interval time between peak contraction of the septum and the lateral wall (P<0.05), that was decreased with dobutamine (4 – 6%) and increased with esmolol (18 –22%). Peak rotation coincided with peak strain in lateral wall. At lower doses of dobutamine, the sequential pattern of contraction was preserved with 15–25% increase in strain and 10 –15% increase in peak rotation that resulted in 30 – 40% increase in dP/dt. With higher doses of dobutamine (>50mcg/kg) and esmolol, the sequential pattern of contraction was lost, with 20 –25% reduction in rotation and 35– 40% reduction in peak dP/dt as compared to baseline.
Conclusions: Coordinated sequential contractile action, with segments moving one after the other like a cascade, is responsible for cardiac rotation which seems to be directly related to systolic function or peak dP/dt.