Abstract 14902: Bimodal Negative dP/dt During Acute Ischemia Is Caused by Transient Regional Premature Relaxation and Ventricular Dyssynchrony: Assessment by Speckle Tracking Echocardiography
Background: Peak −dP/dt, a parameter of left ventricular (LV) relaxation, is known to decrease immediately after coronary occlusion and the timing of peak −dP/dt is shifted earlier creating a bimodal pattern (figure), which disappears after 30–60 s. Although the possible relationship between the bimodal negative dP/dt and abnormal wall motion has been suggested, the details still remain unclear.
Methods: To clarify the cause of transient change in −dP/dt pattern, speckle tracking echocardiography was done to obtain LV short-axis images before, 15 s and 60 s after the left circumflex coronary artery occlusion in 7 dogs along with simultaneous micromanometer measurements of LV pressure and dP/dt. Circumferential strain and strain rate were analyzed in the risk and normal areas.
Results: In the risk area, systolic circumferential strain decreased 15 s after occlusion and premature relaxation (arrowhead) was observed in late systole, while it was not observed in the normal area. This discordance created ventricular dyssynchrony. Peak −dP/dt decreased 15 s after occlusion and timing of peak became earlier, which corresponded with that of peak positive strain rate associated with premature relaxation (arrow). Systolic strain markedly decreased 60 s after occlusion and premature relaxation became smaller resulting in disappearance of dyssynchrony. Peak −dP/dt tended to recover to baseline level at this time. Peak positive strain rate in systole at 60 s significantly decreased compared to that at 15 s (0.35±0.18 vs. 0.75±0.32 /s, p < 0.05).
Conclusions: Premature relaxation in the ischemic area causes ventricular dyssynchrony and the bimodal pattern of peak −dP/dt. Speckle tracking echocardiography is a promising method for the detailed analysis of dyssynchronous wall motion.
- © 2010 by American Heart Association, Inc.