采用二维相位对比速度编码技术研究扩张型心肌病心力衰竭的左心室直流血流动力学特征

Left Intraventricular Direct Flow Hemodynamics of Dilated Cardiomyopathy Using Two-Dimensional Phase Contrast Velocity Encoding Technique

目的采用磁共振二维相位对比速度编码技术测量左心室内直流成分的血流动力学参数,分析扩张型心肌病(DCM)心力衰竭的左心室内血流动力学变化规律。资料与方法前瞻性分析2017年1月—2019年12月于解放军总医院第一医学中心采集的24例DCM心力衰竭患者和21例健康志愿者的心脏磁共振图像。用平衡稳态快速梯度回波序列完成常规电影图像测量左心室射血分数(LVEF)、左心室舒张末期容积(LVEDV)和左心室收缩末期容积(LVESV);用二维相位对比速度编码序列在左心室心底、中部和心尖3个水平短轴位采集垂直成像层面的血流速度,流速编码预设值120 cm/s,每个心动周期划分为24个时相。采用Medviso Segment软件对电影成像和血流成像序列图像进行后处理,获取左心室内血流量、血流速度、血流定向动能(SKE),以健康志愿者为对照组分析DCM心力衰竭患者左心室直流的血流动力学变化规律,并进行合理的血流动力学解释。结果在曲线轮廓特征上,对照组的平均速度、净流量和SKE曲线上呈横置的S形,规律性明显;研究组的曲线缺乏这种规律性。两组血流速度射血峰值与充盈峰值差异有统计学意义(P<0.05),其余指标差异均无统计学意义(P>0.05)。LVEF与心底及心腔中部平均射血速度、心腔中部平均充盈速度呈正相关(r=0.624、0.630、0.610,P<0.01);收缩末期容积/收缩末期容积指数与心腔中部平均射血速度呈负相关(r=-0.611、-0.625,P<0.01),与心底及心尖部平均射血速度呈负相关(r=-0.57~-0.52,P<0.01);舒张末期容积/舒张末期容积指数与3个水平的平均射血速度峰值呈负相关(r=-0.57~-0.48,P<0.01);心排血量与心底及心腔中部平均充盈速度呈正相关(r=0.656、0.634,P<0.01)。除心底部充盈流量峰值与LVEDV/LVESV呈正相关(r=0.516、0.411,P<0.01)外,其余血流量相关参数及SKE与LVEF、LVEDV/LVESV、每搏输出量/每搏输出量指数、心排血量/心脏指数均呈弱相关或无相关(r<0.4)。舒张充盈SKE的达峰时间差异与LVEF呈负相关(r=-0.67,P<0.05)。结论DCM心力衰竭患者左心室直流血流流速峰值与功能参数显著相关,且显著低于正常对照组,舒张充盈SKE的达峰时间差异与LVEF显著相关,反映左心室内直流成分的失同步性,可以定性解释DCM心力衰竭的血流动力学特征。

Purpose Using two-dimensional phase-contrast velocity encoding(2D-PC-VENC)technique to quantify the direct flow inside the left ventricle and detect the alterations in left ventricle flow in patients with dilated cardiomyopathy(DCM).Materials and Methods Twenty-four DCM patients and 21 healthy volunteers in the First Medical Center of PLA General Hospital from January 2017 to December 2019 were enrolled in this study.The cine imaging was acquired using balanced steady-state free precession sequence to determine left ventricular ejection fraction(LVEF),left ventricular end-diastolic volume(LVEDV)and left ventricular end-systolic volume(LVESV).2D-PC-VENC flow imaging was acquired at the levels of basal,middle and apical of left ventricle,perpendicular to the direct flow,presetting the encoding velocity to 120 cm/s.Each cardiac cycle was divided into 24 phases.The hemodynamic measurements,including velocity,flow,signed kinetic energy(SKE)of the direct flow,were obtained by using Medviso Segment software.The hemodynamic measurements in DCM patients were compared with the healthy subjects.Results The curves of the average velocity,net flow and SKE in normal controls showed regular transverse S profiles,while those of the DCM patients were not.Velocity of peak systolic and diastolic through-plane flows were significantly decreased in DCM patients compared to the healthy volunteers in each level(P<0.05),but no statistical difference in other indexes was observed between the two groups(P>0.05).LVEF had a positive correlation to the average eject velocities at the basal/middle levels and the average filling velocities at the middle levels(r=0.624,0.630 and 0.610,P<0.01);ESV/ESVI had a negative correlation to the average eject velocities at the middle levels(r=-0.611 and-0.625,P<0.01)and a moderate negative correlation to the average eject velocities at basal/apical levels(r=-0.57--0.52,P<0.01);end-diastolic volume/end-diastolic volume index had negative correlation to the average eject velocities at three levels(r=-0.57--0.48,P<0.01);cardiac output had a strong correlation to the average fill velocities at the basal/middle levels(r=0.656 and 0.634,P<0.01).Except for the peak filling flow at the basal level was positively correlated with EDV/ESV(r=0.516 and 0.411,P<0.01),there was no significant correlation between other flow-related parameters and SKE with LVEF,LVEDV/LVESV,SV/SVI,or cardiac output/cardiac index(r<0.4).The difference of time to peak was negative correlated to the LVEF(r=-0.67,P<0.05).Conclusion The quantitative hemodynamic measurements,the peaks of velocity and the difference of time to peak of SKE curves are significantly correlated to the LVEF,indicating the dissynchrony of the direct flow inside the left ventricle,could be a qualitative interpretation of the hemodynamic patterns of the heart failure.