Efficacy Of Microbubble-enhanced Sonothrombolysis On Platelet-rich Thrombi And Erythrocyte-rich Thrombi Of Different Ages

Background and objective:microbubble-enhanced sonothrombolysis has attracted more and more attention in cardiovascular filed,due to its economy,convenience,and safe profiles.However,there are two important problems remained that challenge the thrombolytic effect of microbubble-enhanced sonothrombolysis.Firstly,most of previous studies have focused on the treatment effect of microbubble-enhanced sonothrombolysis on red thrombus while the same effect on white thrombus is still unclear.Secondly,the thrombus age in most relevant studies stay in 3-6 hour,but the thrombus age varies from hours to tens of hours for criminal thrombosis that cause ischemic events in clinical practice;for thrombus with older age,whether the microbubble-enhanced sonothrombolysis is effective or not is also remained unclear.Therefore,in this study we conducted experiments both in vitro and vivo to investigate the effects of microbubble-enhanced sonothrombolysis therapy in different age of platelet-rich thrombus(PRT)and erythrocyte-rich thrombus(ERT),and intend to guide clinical practice to select the most reasonable time window for microbubble-enhanced sonothrombolysis therapy.Materials and Methods:in vitro,PRT and ERT were prepared in extracorporeal circulation device by rat peripheral blood.In vivo model,PRT was prepared by ferric chloride method and ERT was prepared by clamping the arteria carotis communis.HE staining and electron microscopy were used to identify the thrombus in vivo.HE staining and immunohistochemistry were used to identify the thrombus in vitro.Models were randomly divided into 4 groups based on the type and age of thrombus no matter in vitro or vivo.We performed microbubble-enhanced sonothrombolysis therapy in vitro and carotid artery thrombosis model by using diagnostic ultrasound(frequency 2MHz,mechanical index MI 1.9)and lipid microbubbles.Two-dimensional ultrasound was used to determine the percentage and the thrombolysis rate of the cross-sectional area of the lumen,and the carotid artery recanalization rate and the mean blood flow velocity.The above indexes of the four groups were recorded,and the differences among them were compared by one-way ANOVA and chi square test.Results:In vitro,compared with 3h PRT and ERT group respectively,12h PRT and ERT group had significantly decreased in the lumen cross-sectional area(99.04±12.02%VS 121.12±13.21%;110.56±10.89%VS 130.09±15.34%)and thrombolytic rate(35.01±4.24%VS 39.38±7.09%;38.54±3.89%VS 42.14±5.17%)(p<0.05);compared with 3h PRT and ERT group respectively,24h PRT and ERT group also had significantly decreased in the lumen cross-sectional area(58.43±12.28%VS 121.12±13.21%;89.34±16.47%VS 130.09±15.34%)and thrombolytic rate(20.04±8.19%VS 39.38±7.09%;30.21±5.26%VS 42.14±5.17%)(p<0.05);in addition,the lumen cross-sectional area(58.43±12.28%VS 89.34±16.47%and thrombolytic rate(20.04±8.19%VS 30.21±5.26%)in 24h PRT group were both significantly as decreased compared with 24h ERT group(p<0.05);no significant differences of above mentioned indicators were found between PRT and ERT group both in 3 and 12h.In vivo,compared with 3h PRT and ERT group respectively,12h PRT and ERT group had significantly decreased in vascular recanalization rate(66.67%VS 83.33%;75%VS 91.67%)and the average blood flow velocity of common carotid artery(0.18±0.03m/s VS 0.21±0.02m/s;0.19±0.02m/s VS 0.22±0.01 m/s)(p<0.05);compared with 3h PRT and ERT group respectively,24h PRT and ERT group had significantly decreased in vascular recanalization rate(41.67%VS 83.33%;58.33%VS 91.67%)and the average blood flow velocity of common carotid artery(0.13±0.02m/s VS 0.21±0.02m/s;0.16±0.01m/s VS 0.22±0.01m/s)(p<0.05);in addition,the vascular recanalization rate(41.67%VS 58.33%)and the average blood flow velocity of common carotid artery(0.13±.0.02 m/s VS 0.16±0.01 m/s)in 24h PRT group were both significantly as decreased compared with 24h ERT group(p<0.05);no significant differences of above mentioned indicators were found between PRT and ERT group both in 3 and 12h.With the increase of coagulation age,the pathological examination of thrombus in vivo and in vivo both showed that PRT and ERT were denser in histology.Conclusions:The effect of ultrasound combined with microbubbles on the dissolution of PRT and ERT both in vivo and in vitro was decreased along with the increase of thrombus age,especially for PRT,which may attribute to the gradual densification of the thrombus.