利用MRI Tagging分析β受体阻滞剂对左室心肌运动的影响

Effects of incremental beta blocker dosing on myocardial mechanics of the left ventricle：MRI 3D Tagging insight

目的 探讨不同剂量β受体阻滞剂对左室心肌运动特征的影响及其作用机制.方法 13名志愿者注射不同剂量的短效β受体阻滞剂Esmolol,每个注射剂量起效4 min后利用MRI Tagging对左室心肌圆周向收缩运动、放射向收缩运动及长轴收缩运动进行磁化标记追踪,对获得的心肌运动结果进行心肌最大收缩程度、达到最大收缩时间、收缩速度及心肌做功分析.结果 注射小剂量Esmolol（5～25 μg·kg-1·min^-1）时,心肌运动程度增加,所需时间缩短,心肌做功增加;而当剂量增加至50～150 μg·kg-1·min^-1时,心肌运动明显较未用药时减弱,可以看到β受体阻滞剂Esmolol的负性肌力作用开始显现.结论 小剂量β受体阻滞剂与大剂量相比,更易对心肌运动产生正性肌力作用,这可能与不同种类心肌细胞表面β受体分布差异有关.

Objective MRI Tagging was applied to detect different effects on myocytes by different doses of β-blocker.Methods 13 healthy volunteers attended this research by MRI tagging during escalated administration of Esmolol.The circumferential,longitudinal and radial myocardial shortening was determined for each dose.The curves were analyzed for peak value,time-to-peak,upslope,and area-under-the-curve.Results At low doses,from 5-25 μg·kg-1·min-1,the peak value increased,while time-to-peak decreased,yielding a steeper upslope.Combining the values revealed a left shift of the curves at low doses when compared to the curve without Esmolol.At doses of 50-150 μg·kg^-1·min^-1,a right shift with flattening occurred indicating less pronounced shortening as sign of negative inotropy.Conclusion Differences were found in healthy volunteers in the myocardial effects of beta-blockade at low compared to high dosage.It is tempting to speculate that the response to β-blockade could be even more pronounced in patients suffering from ventricular hypertrophy due to the higher prevalence of the transversely intruding cardiomyocytes.MRI tagging is helpful to monitor dosing.