Cleveland Clinic, Cleveland, Ohio, USA.
J Am Soc Echocardiogr. 2013 Feb;26(2):185-91. doi: 10.1016/j.echo.2012.10.008. Epub 2012 Dec 3.
The definition of normal values of left ventricular global longitudinal strain (GLS), global circumferential strain, and global radial strain is of critical importance to the clinical application of this modality. The investigators performed a meta-analysis of normal ranges and sought to identify factors that contribute to reported variations.
MEDLINE, Embase, and the Cochrane Library database were searched through August 2011 using the key terms "strain," "speckle tracking," "left ventricle," and "echocardiography" and related phrases. Studies were included if the articles reported left ventricular strain using two-dimensional speckle-tracking echocardiography in healthy normal subjects, either in the control group or as a primary objective of the study. Data were combined using a random-effects model, and effects of demographic, hemodynamic, and equipment variables were sought in a meta-regression.
The search identified 2,597 subjects from 24 studies. Reported normal values of GLS varied from -15.9% to -22.1% (mean, -19.7%; 95% CI, -20.4% to -18.9%). Normal global circumferential strain varied from -20.9% to -27.8% (mean, -23.3%; 95% CI, -24.6% to -22.1%). Global radial strain ranged from 35.1% to 59.0% (mean, 47.3%; 95% CI, 43.6% to 51.0%). There was significant between-study heterogeneity and inconsistency. The source of variation was sought between studies using meta-regression. Blood pressure, but not age, gender, frame rate, or equipment, was associated with variation in normal GLS values.
The narrowest confidence intervals from this meta-analysis were for GLS and global circumferential strain, but individual studies have shown a broad range of strain in apparently normal subjects. Variations between different normal ranges seem to be associated with differences in systolic blood pressure, emphasizing that this should be considered in the interpretation of strain.
左心室整体纵向应变（GLS）、整体圆周应变和整体径向应变的正常值定义对该技术的临床应用至关重要。研究者对正常值范围进行了荟萃分析，并试图确定导致报告变异的因素。
通过关键词“应变”、“斑点追踪”、“左心室”和“超声心动图”以及相关短语，检索 2011 年 8 月前的 MEDLINE、Embase 和 Cochrane 图书馆数据库。如果文章报道了使用二维斑点追踪超声心动图在健康正常受试者中的左心室应变，且研究对象为对照组或作为研究的主要目标，则将其纳入研究。使用随机效应模型合并数据，并在荟萃回归中寻找人口统计学、血液动力学和设备变量的影响。
搜索共确定了 24 项研究的 2597 名受试者。报道的 GLS 正常值范围为-15.9%至-22.1%（平均值为-19.7%；95%置信区间：-20.4%至-18.9%）。正常整体圆周应变范围为-20.9%至-27.8%（平均值为-23.3%；95%置信区间：-24.6%至-22.1%）。整体径向应变范围为 35.1%至 59.0%（平均值为 47.3%；95%置信区间：43.6%至 51.0%）。研究间存在显著的异质性和不一致性。使用荟萃回归在研究间寻找变异的来源。血压，而不是年龄、性别、帧率或设备，与 GLS 正常值的变化相关。
本荟萃分析得到的最窄置信区间是 GLS 和整体圆周应变，但个别研究表明，在正常的个体中应变范围较广。不同正常范围之间的差异似乎与收缩压的差异有关，这强调了在解释应变时应考虑这一点。
