P469The value of myocardial contrast echocardiography in evaluating the relationship between myocardial perfusion and cardiac resynchronization therapy: an animal study.

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Purpose: To establish an animal model of heart failure and cardiac resynchronization therapy (CRT) after myocardial infarction. Myocardial contrast echocardiography (MCE) was used to quantitatively analyze the myocardial perfusion in order to evaluate the relationship between myocardial perfusion, cardiac synchrony and the response of CRT.Methods: Twenty adult Beagles were randomly divided into group A (CRT group, n=10) and group B (non-CRT group, n=10). All of them had heart failure after a ligature in the first diagonal branch. A left ventricular epicardial lead, a right atrium and a right ventricle leads together with the pacemaker were implanted. The pacing was started in Group A after myocardial infarction, but was not started in group B. MCE was performed before and 2 weeks after myocardial infarction, 2 weeks and 4 weeks after CRT. Speckle tracking imaging was used to evaluate standard deviation of time to peak of transmural regional circumferential strain (Cir 12SD) and radial strain (R 12SD).Results: Two dogs in group A and one dog in group B died of ventricular fibrillation after myocardial infarction, other dogs successfully completed the study. The myocardial blood flow (MBF) in normal Beagles was 74±4dB/s. The MBF of myocardial infarction region was 9±2dB/s. The MBF of group A was significantly higher than that of group B (2 weeks after CRT [35±3dB/s] vs. [16±3dB/s], 4 weeks after CRT [54±5dB/s] vs. [24±4dB/s], all P<0.05). After 4 weeks therapy, LVEF in group A was increased from 32.8% to 56.0%, while in group B it was increased form 29.0% to 45.1% (p<0.05). The response of CRT in group A was 83% when LVEF≥45% was defined effectively response to CRT after 4 weeks therapy. Cir 12SD and R 12SD in group A showed a significant difference before and after CRT therapy (39.2ms vs. 22.3ms, 150.1ms vs. 37.3ms, all P<0.05). They were also significantly improved compared to group B (22.3ms vs. 43.3ms, 37.3ms vs. 59.3ms, all P<0.05). It prompted that CRT could improve cardiac synchrony and improve myocardial perfusion. The correlation coefficient between MBF and LVEF after CRT is 0.715. When MBF>30dB/s was defined as a cut-off value before CRT, the sensitivity and specificity of predicting the response of CRT are 66.7% and 80% respectively.Conclusions: CRT can improve cardiac synchrony and myocardial perfusion in the animal model. The MBF value can represent the level of myocardial perfusion. The MBF value and the response of CRT are positively correlated. The sensitivity and specificity are 66.7% and 80% when MBF>30dB/s was defined as a cut-off value for predicting the response of CRT.

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