Impact On Myocardial Permeability Of Rabbit In Contrast Echocardiography

BackgroundWith the application of ultrasound contrast agent (UCA), more and more attention had been paid to the bioeffects induced by contrast ultrasonography. Many studies indicated that intravenous injection of microbubbles UCA could greatly increase absorption of ultrasound energy and enhance cavitation or bioeffects as effective cavitational nuclei. Bioeffects like increased myocardial vascular permeability and petechial hemorrhages could be found during contrast echocardiography at high mechanic index. These bioeffects tended to be magnified by increase in microbubbles injection and ultrasound energy. So far, the bioeffects research was limited to some imaging modalities and small animal like rat. Other potential impact factors like heart rate, large animal model have not investigated.Objectives:1. To identify that the myocardial permeability in contrast echocardiography could be reproduced on bigger animal level.2. To investigate the bioeffects in different imaging modalities.3. To explore whether heart rate is an independent impact factor on myocardial permeability in contrast echocardiography.4. To compare the myocardial bioeffects between therapeutic ultrasound and diagnostic ultrasound.Methods:All rabbits were anesthetized and prepared. Ultrasound was insonated at central sternal position using a GE Vivid 7 ultrasound system. A lipid ultrasound contrast agent, "zhifuxian" was injected from ear vein.The experimental groups were divided as table followed. Electrocardiogram was recorded during all ultrasound exposure. Evans-blue (EB) was used as a blood-pool tracer agent and the EB content in myocardium was harvested by formamide extrudation. EB leakage of myocardium was also quantified by visual scores. At last, pathology of myocardium was performed using H.E.Results:No premature heartbeat was found in the simple ultrasound control group, but premature heartbeats were found in all the others. There were no differences among the experimental groups.The myocardial EB content was significantly less in the simple ultrasound group than that of the others. It was particularly higher in the high heart rate group and the stress group than that of the slow heart rate group. The triggered imaging group tended to produce more EB leakage than that of the continuous imaging group. No significant differences were found between therapeutic ultrasound and diagnostic ultrasound in continuous imaging modality.In pathological exam, there was no apparent cardiomyocyte injury. Red blood cells and lymphocytes exudation were found in interstitial myocardium of all the experimental groups except the simple ultrasound control group.Conclusions:1. Increased myocardial microvascular permeability during high MI contrast echocardiography happened in rabbit. 2. Triggered imaging modality and high heart rate are individual impact factors of myocardial permeability during contrast echocardiography.3. Low intensity therapeutic ultrasound produces similar bioeffects as diagnostic ultrasound.