Urheim S, Edvardsen T, Torp H, Angelsen B, Smiseth O A
Institute for Surgical Research and The Department of Cardiology, Rikshospitalet, University of Oslo, Norway.
Circulation. 2000 Sep 5;102(10):1158-64. doi: 10.1161/01.cir.102.10.1158.
Myocardial strain is a measure of regional deformation, and by definition, negative strain means shortening and positive strain, elongation. This study investigates whether myocardial strain can be measured by Doppler echocardiography as the time integral of regional velocity gradients, using sonomicrometry as reference method.
In 13 anesthetized dogs, myocardial longitudinal strain was measured on apical images as the time integral of regional Doppler velocity gradients. Ultrasonic segment-length crystals were placed near the left ventricular (LV) apex and near the base. Apical ischemia was induced by occluding the left anterior descending coronary artery (LAD), and preload was increased by saline. Percentage systolic strain by Doppler correlated well with strain by sonomicrometry (y=0.82x-1.79, r=0.92, P<0.01). During LAD occlusion, apical myocardium became dyskinetic, as indicated by positive strain values and negative Doppler velocities. At the LV base, myocardial strain by Doppler, strain by sonomicrometry, and velocity of shortening by sonomicrometry (dL/dt) were unchanged during apical ischemia. However, myocardial Doppler velocities at the base decreased from 4.2+/-0.7 (+/-SEM) to 2.7+/-0. 4 cm/s (P<0.05), probably reflecting loss of motion caused by tethering to apical segments. Volume loading increased myocardial Doppler velocities from 2.2+/-0.3 to 4.1+/-0.8 cm/s (P<0.05) and Doppler-derived strain from -12+/-1% to -22+/-2% (P<0.05), whereas peak LV elastance remained unchanged.
Myocardial strain by Doppler echocardiography may represent a new, powerful method for quantifying regional myocardial function and is less influenced by tethering effects than Doppler tissue imaging. Like myocardial Doppler velocities, strain is markedly load-dependent.
心肌应变是区域变形的一种测量指标，根据定义，负应变意味着缩短，正应变意味着伸长。本研究使用超声心动图作为参考方法，探讨是否可以通过将心肌应变测量为区域速度梯度的时间积分来进行多普勒超声心动图测量。
在13只麻醉犬中，在心尖图像上测量心肌纵向应变，作为区域多普勒速度梯度的时间积分。将超声节段长度晶体放置在左心室（LV）心尖附近和基部附近。通过闭塞左前降支冠状动脉（LAD）诱导心尖缺血，并通过盐水增加前负荷。多普勒测量的收缩期应变百分比与超声心动图测量的应变相关性良好（y = 0.82x - 1.79，r = 0.92，P < 0.01）。在LAD闭塞期间，心尖心肌运动障碍，表现为正应变值和负多普勒速度。在LV基部，在心尖缺血期间，多普勒测量的心肌应变、超声心动图测量的应变以及超声心动图测量的缩短速度（dL/dt）均未改变。然而，基部的心肌多普勒速度从4.2±0.7（±SEM）降至2.7±0.4 cm/s（P < 0.05），这可能反映了由于与心尖节段相连而导致的运动丧失。容量负荷使心肌多普勒速度从2.2±0.3增加到4.1±0.8 cm/s（P < 0.05），多普勒衍生应变从-12±1%增加到-22±2%（P < 0.05），而LV峰值弹性保持不变。
多普勒超声心动图测量的心肌应变可能代表一种新的、强大的量化区域心肌功能的方法，并且比多普勒组织成像受连接效应的影响更小。与心肌多普勒速度一样，应变明显依赖于负荷。
