Kowalski M, Herregods M-C, Herbots L, Weidemann F, Simmons L, Strotmann J, Dommke C, D'hooge J, Claus P, Bijnens B, Hatle L, Sutherland G R
University Hospital Gasthuisberg, Department of Cardiology, Leuven, Belgium.
Eur J Echocardiogr. 2003 Jun;4(2):81-91. doi: 10.1053/euje.2002.0174.
Ultrasonic strain rate and strain can characterize regional one-dimensional myocardial deformation at rest. In theory, these deformation indices could be used to quantify normal or abnormal regional function during a dobutamine stress echo test.
The aims of our pilot study were threefold: (1) to determine the percentage of segments in which interpretable strain rate/strain data could be obtained during routine dobutamine stress echo, (2) to establish whether either the increase in heart rate or artefacts induced by respiration during dobutamine stress echo would influence analysis by degrading the data and (3) to determine the optimal frame rate vs image sector angle settings for data acquisition. Furthermore, although the detection of ischaemia was not to be addressed specifically in this study, we would describe the findings on the potential clinical role of regional deformation vs velocity imaging in detecting ischaemia-induced changes.
A standard dobutamine stress echo protocol was performed in 20 consecutive patients with a history of chest pain (16 with angiographic coronary artery disease and four with normal coronary angiograms). DMI velocities were acquired at baseline, low dose, peak dose, and recovery. To evaluate radial function (basal segment of the left ventricle posterior wall segment), parasternal LAX, SAX views were used. For long axis function data were acquired (4-CH, 2-CH views) from the septum; lateral, inferior and anterior left ventricle walls. Data was acquired using both 15 degrees (>150 frames per second (fps) and 45 degrees (115fps) sector angles. During post-processing each wall was divided into three segments: basal, mid and apical. Strain rate/strain values were averaged over three consecutive heart cycles.
Data was obtained from 1936 segments, of which only 54 had to be excluded from subsequent analysis (2.8%) because of suboptimal quality. An increase in heart rates (up to 150/min) was not associated with a significant reduction in the number of interpretable segments. There was a significant correlation between maximal systolic strain rate/strain values obtained at narrow and at wide sector angles (e.g. a correlation for the septal segments: r=0.73,P <0.001 for strain rate, and r=0.71; P<0.001 for strain). The correlation for the timing of events obtained from narrow and wide sector angles was weaker. This would indicate that there was the insufficient temporal resolution for the latter acquisition method. Normal and abnormal regional strain rate/strain responses to an incremental dobutamine infusion were defined. In normal segments, maximal systolic strain rate values increased continuously from baseline, reaching the highest values at the peak dose of dobutamine. The segmental strain response was different. For strain, there was an initial slight increase at low dose of dobutamine (5, 10 microg/kg/min), but no further increase with increasing dose. A pattern representing an ischaemic response was identified and described.
The feasibility study would suggest that with appropriate data collection and post-processing methodologies, strain rate/strain imaging can be applied to the quantification of dobutamine stress echo. However, appropriate post-processing algorithms must be introduced to reduce data analysis time in order to make this a practical clinical technique.
超声应变率和应变能够表征静息状态下局部一维心肌变形。理论上，这些变形指标可用于量化多巴酚丁胺负荷超声心动图检查期间的正常或异常局部功能。
我们的初步研究有三个目的：（1）确定在常规多巴酚丁胺负荷超声心动图检查期间能够获取可解释的应变率/应变数据的节段百分比；（2）确定多巴酚丁胺负荷超声心动图检查期间心率增加或呼吸引起的伪像是否会因数据质量下降而影响分析；（3）确定数据采集的最佳帧率与图像扇角设置。此外，尽管本研究不会专门探讨缺血检测问题，但我们将描述关于局部变形与速度成像在检测缺血性变化中的潜在临床作用的研究结果。
对20例有胸痛病史的连续患者（16例有冠状动脉造影证实的冠心病，4例冠状动脉造影正常）进行标准多巴酚丁胺负荷超声心动图检查。在基线、低剂量、峰值剂量和恢复阶段采集心肌速度成像（DMI）数据。为评估径向功能（左心室后壁基底节段），采用胸骨旁左前斜（LAX）、短轴（SAX）视图。对于长轴功能，从室间隔、左心室侧壁、下壁和前壁采集数据（四腔心、两腔心视图）。使用15度（>150帧/秒（fps））和45度（115fps）扇角采集数据。在后期处理过程中，将每个壁分为三个节段：基底节段、中间节段和心尖节段。应变率/应变值在连续三个心动周期内进行平均。
从1936个节段获取了数据，其中仅54个节段（2.8%）因质量欠佳而被排除在后续分析之外。心率增加（高达150次/分钟）与可解释节段数量的显著减少无关。在窄扇角和宽扇角下获得的最大收缩期应变率/应变值之间存在显著相关性（例如，室间隔节段的相关性：应变率r = 0.73，P < 0.001；应变r = 0.71，P < 0.001）。从窄扇角和宽扇角获得的事件发生时间的相关性较弱。这表明后一种采集方法的时间分辨率不足。定义了正常和异常节段对多巴酚丁胺递增输注的应变率/应变反应。在正常节段中，最大收缩期应变率值从基线开始持续增加，在多巴酚丁胺峰值剂量时达到最高值。节段应变反应有所不同。对于应变，在多巴酚丁胺低剂量（5、10微克/千克/分钟）时最初有轻微增加，但随着剂量增加没有进一步增加。识别并描述了一种代表缺血反应的模式。
可行性研究表明，采用适当的数据收集和后期处理方法，应变率/应变成像可应用于多巴酚丁胺负荷超声心动图的量化分析。然而，必须引入适当的后期处理算法以减少数据分析时间，使其成为一种实用的临床技术。
