Pierre-Justin Gilbert, Lancellotti Patricio, Pierard Luc A
Department of Cardiology, University Hospital Sart Tilman, B-4000 Liège, Belgium.
Int J Cardiol. 2005 Jun 22;102(1):21-31. doi: 10.1016/j.ijcard.2004.03.086.
Evaluation and quantification of regional myocardial function remain a challenge for imaging techniques in stress test. Strain and strain rate can be calculated from velocity gradients in time and space. This new technique has been developed to allow quantifiable stress echocardiography. The aim of this study was to define normal regional strain rate and strain values for both radial and deformation longitudinal myocardial deformation during supine bicycle.
Real-time color Doppler myocardial velocities were acquired as data superimposed on an underlying two-dimensional (2D) grey-scale image at a frame rate > 150/s, a depth of 16 cm, and a sector angle of 60 degrees in 18 healthy volunteers, mean age 34+/-7 years (25-43 years). During acquisition, a complete cardiac cycle of each view was acquired at rest and during supine bicycle (from 25 W to maximal charge). Maximal systolic velocity, strain rate, and strain were processed offline for both radial (basal posterior wall segment) and longitudinal (septum, lateral, inferior, anterior walls) function. For analysis, each wall was divided into three segments (basal, mid, apical). All the velocity and SR/S values were averaged over three consecutive cycles.
During exercise, heart rate and systolic blood pressure increased significantly from rest to peak stress (69+/-14 vs. 152+/-7 beats/min, p < 0.0001 and 118+/-9 vs. 178+/-28 mm Hg, p < 0.001). For the Lax view, both the mean velocity and mean strain rate increased significantly between rest and peak exercise, respectively, for the velocity and for the strain rate. Similarly is said for the Sax view. In contrast, the systolic strain response was biphasic during exercise, basal, mid, and apical segments of walls showed a significant increase of velocity in each workload step. The resting base-apex velocity gradient observed at rest remained in all walls throughout supine bicycle. The mean peak systolic SR data were homogeneous throughout in all segments analysed at rest. This homogeneity remained at peak exercise. The SR increased significantly between rest and peak exercise, respectively, p < 0.0117. The segmental systolic strain response was biphasic.
This study demonstrated that strain rate imaging may represent a new and interesting method for quantifying regional myocardial function during supine bicycle, which appears to be less influenced by tethering than Doppler tissue imaging. Further studies are needed to determine whether this approach will be clinically useful.
区域心肌功能的评估和量化仍然是应力测试成像技术面临的挑战。应变和应变率可根据时间和空间中的速度梯度计算得出。这项新技术的开发是为了实现可量化的应力超声心动图检查。本研究的目的是确定仰卧位自行车运动期间径向和纵向心肌变形的正常区域应变率和应变值。
在18名健康志愿者（平均年龄34±7岁，25 - 43岁）中，以>150帧/秒的帧率、16厘米的深度和60度的扇形角度获取叠加在二维（2D）灰度图像上的实时彩色多普勒心肌速度数据。在采集过程中，在静息状态和仰卧位自行车运动期间（从25瓦到最大负荷）获取每个视图的完整心动周期。对径向（基底后壁节段）和纵向（室间隔、侧壁、下壁、前壁）功能的最大收缩速度、应变率和应变进行离线处理。为了进行分析，将每个壁分为三个节段（基底、中间、心尖）。所有速度和SR/S值在连续三个心动周期上进行平均。
运动期间，心率和收缩压从静息状态到峰值应力显著增加（69±14对152±7次/分钟，p<0.0001；118±9对178±28毫米汞柱，p<0.001）。对于Lax视图，静息状态和峰值运动之间，速度和应变率的平均速度和平均应变率分别显著增加。Sax视图也是如此。相比之下，运动期间收缩期应变反应呈双相性，壁的基底、中间和心尖节段在每个工作量步骤中速度均显著增加。仰卧位自行车运动期间，静息时观察到的静息基底部 - 心尖部速度梯度在所有壁中均保持。静息时分析的所有节段的平均峰值收缩期SR数据在整个过程中是均匀的。这种均匀性在峰值运动时仍然存在。静息状态和峰值运动之间，SR分别显著增加，p<0.0117。节段性收缩期应变反应呈双相性。
本研究表明，应变率成像可能是一种新的、有趣的方法，用于量化仰卧位自行车运动期间的区域心肌功能，与多普勒组织成像相比，它似乎受牵拉的影响较小。需要进一步研究以确定这种方法是否具有临床实用性。
