运动负荷状态下心肌运动和形变特点——人体超声三维斑点追踪应变研究

Characteristics of Myocardial Motion and Deformation under Exercise Stress:A Human Echocardiographic Study by 3-Dimensional Speckle Tracking Imaging

目的:利用三维斑点追踪技术(3D-STE)探究健康男性青年在递增负荷运动过程中左心室心肌运动和形变的特点和规律,初步评价在心脏几何形变和心肌力学状态发生变化时的心肌收缩功能储备。方法:研究对象为15名健康男性青年,年龄26.1±6.3岁,身高174.4±4.8 cm,体重72.0±8.2 kg。受试者以平卧位姿势蹬踏功率自行车,强度为50 W起步,每3 min递增25 W,最高达到125 W,蹬车频率始终保持在60转/分钟。在静息状态和每级负荷1 min后以及运动后3 min分别采集心脏常规超声指标、三维斑点追踪技术指标,全程监测心率和血压。获取的指标包括心率(HR)、收缩压(SBP)、舒张压(DBP)等心脏基础指标;左心室射血分数(LVEF)、每搏输出量(SV)、心输出量(CO)等心脏常规超声功能指标;左心室心肌整体纵向应变(GLS)、整体圆周应变(GCS)、整体面积应变(GAS)、整体旋转角度峰值(Rotation)、整体扭力(Tortion)和左心室心肌16节段纵向应变等3D-STE相关指标。结果:在递增负荷运动过程中,HR、SBP、DBP、LVEF、SV、CO等指标随负荷强度的增强而增加,具有统计学意义(P<0.01)。GLS、GCS、GAS绝对值在运动过程中出现显著性变化(P<0.01),表现为在运动开始后增加,GLS、GAS在运动负荷为75 W时达到最高,GCS在运动负荷为100 W时达到最高,然后均出现降低趋势,但始终高于静息状态;运动后3 min基本恢复。Rotation、Tortion在运动过程中有增加趋势,但差异无统计学意义(P>0.05)。左心室心肌节段中心尖部纵向应变值最大、中间段次之、基底部最小。其中心尖部前侧壁、下壁,中间段下壁、后间隔的纵向应变绝对值变化具有统计学意义(P<0.05)。结论:三维斑点追踪技术可以初步评价运动负荷状态下心肌储备功能,在递增负荷运动过程中,运动负荷状态下心脏泵血功能增强,左心室心肌形变幅度随着运动负荷的递增呈现先升高后降低的趋势,始终高于静息状态,主要以心尖部和中间段收缩增强为主。

Objective To observe the characteristics and patterns of left ventricular myocardial mo⁃tion and deformation during incremental load exercise by three-dimensional speckle tracking technology(3D-STE),and to evaluate myocardial contractile functional reserve in such physical condition.Meth⁃ods Fifteen healthy male youths were selected as the subject,with an average age,height,and weight of 26.1±6.3 years,174.4±4.8 cm and 72.0±8.2 kg,respectively.They pedaled power bicycles in a lying position at an intensity of 50 W to start with,with an incremental increase of 25 W every 3 min up to a maximum of 125 W,and the riding frequency maintaining at 60 rpm.Their heart rate and blood pressure were monitored all the time,and data at rest,as well as 1 and 3 minutes after each loading were collected by conventional ultrasound and 3D-STE,including basic cardiac indexes such as heart rate(HR),systolic blood pressure(SBP),diastolic blood pressure(DBP),routine ultra⁃sound cardiac function indexes such as left ventricular ejection fraction(LVEF),stroke volume(SV),and cardiac output(CO),as well as 3D-STE indices such as the left ventricular global longitudinal strain(GLS),global circumferential strain(GCS),global area strain(GAS),overall rotation and tor⁃sion,and 16-segment longitudinal strain of the LV myocardium.Results During the incremental load exercise,the average HR,SBP,DBP,LVEF,SV and CO increased significantly with the enhance⁃ment of load intensity(P<0.01).The absolute values of GLS,GCS and GAS changed significantly dur⁃ing the exercise(P<0.01),as they increased right after the beginning of the exercise,with GCS reach⁃ing the highest at the exercise load of 100 W and the other two at 75 W.Then all of them showed a decreasing trend but still higher than the resting state,but recovered 3 minutes after exercise.More⁃over,the overall rotation and torsion increased during exercise,but not of significant differences(P>0.05).The longitudinal strain value of the left ventricular myocardial segments was the largest in the apical part,followed by the middle part,and the smallest at the base.Among them,significant differ⁃ences were observed in the change of the absolute value of longitudinal strain in the anterolateral and inferior walls of the apical part,the inferior wall of the middle segment,and the posterior septum(P<0.05).Conclusion The three-dimensional speckle tracking technique can evaluate the myocardial re⁃serve function under exercise stress preliminarily.During the incremental load exercise,the pumping function of the heart enhances,and the deformation of left myocardium increases and then decreases,but always bigger than that of the resting state,with mainly the contraction of the apical and middle segments of the myocardium.