Department of Medicine, University of Chicago Medical Center, Chicago, Illinois.
Centro Privado de Cardiologia, Yerba Buena, Tucumán, Argentina.
J Am Soc Echocardiogr. 2018 Mar;31(3):297-303. doi: 10.1016/j.echo.2017.10.005. Epub 2017 Nov 23.
Although left ventricular global longitudinal strain (GLS) is an index of systolic function recommended by the guidelines, poor image quality may hamper strain measurements. While contrast agents are commonly used to improve endocardial visualization, no commercial speckle-tracking software is able to measure strain in contrast-enhanced images. This study aimed to test the accuracy of speckle-tracking software when applied to contrast-enhanced images in patients with suboptimal image quality.
We studied patients with a wide range of GLS values who underwent transthoracic echocardiography. Protocol 1 included 44 patients whose images justified use of contrast but still allowed noncontrast speckle-tracking echocardiography (STE), which was judged as accurate and used as a reference. Protocol 2 included 20 patients with poor image quality that precluded noncontrast STE; cardiac magnetic resonance- (CMR-) derived strain was used as the reference instead. Half the manufacturer recommended dose of a commercial contrast agent (Definity/Optison/Lumason) was used to provide partial contrast enhancement. Higher than normal mechanical indices (0.6-0.7) and lowest frequency range for maximal penetration settings were used for imaging. GLS was measured (Epsilon) with and without contrast-enhanced images and by CMR-derived feature tracking (TomTec). Comparisons included linear regression and Bland-Altman analyses.
The contrast STE analysis failed in 4/64 patients (6%). Manual corrections were needed to optimize tracking with contrast in all patients. GLS measurements were in good agreement between contrast and noncontrast images (r = 0.85; mean GLS in the contrast images, -12.9% ± 4.7%; bias, 0.34% ± 2.4%). Good agreement was also noted between contrast STE- and CMR-derived strain (r = 0.83; mean, GLS -13.5% ± 4.0%; bias, 0.72% ± 2.5%).
We found that GLS measurements from contrast-enhanced images are feasible and accurate in most patients, even in those with poor image quality that precludes strain measurements without contrast enhancement.
尽管左心室整体纵向应变（GLS）是指南推荐的收缩功能指标，但图像质量差可能会妨碍应变测量。虽然对比剂常用于改善心内膜可视化，但没有商业斑点追踪软件能够测量增强图像中的应变。本研究旨在测试在图像质量差的患者中应用增强对比图像时斑点追踪软件的准确性。
我们研究了接受经胸超声心动图检查的具有广泛 GLS 值的患者。方案 1 包括 44 例患者，其图像可使用对比剂，但仍允许进行非对比斑点追踪超声心动图（STE），我们判断该方法准确，并将其作为参考。方案 2 包括 20 例图像质量差而无法进行非对比 STE 的患者；取而代之的是心脏磁共振（CMR）衍生应变作为参考。使用一半商业对比剂（Definity/Optison/Lumason）的推荐剂量进行部分对比增强。使用高于正常的机械指数（0.6-0.7）和最大穿透设置的最低频率范围进行成像。使用和不使用对比增强图像以及 CMR 衍生的特征追踪（TomTec）测量 GLS（Epsilon）。比较包括线性回归和 Bland-Altman 分析。
对比 STE 分析在 64 例患者中失败 4 例（6%）。所有患者都需要手动校正以优化对比跟踪。对比和非对比图像之间的 GLS 测量值具有良好的一致性（r=0.85；对比图像的平均 GLS，-12.9%±4.7%；偏差，0.34%±2.4%）。对比 STE 和 CMR 衍生应变之间也存在良好的一致性（r=0.83；平均 GLS-13.5%±4.0%；偏差，0.72%±2.5%）。
我们发现，即使在图像质量差而无法进行增强对比应变测量的患者中，增强对比图像的 GLS 测量值也是可行且准确的。
