University of Chicago Medical Center, Chicago, Illinois; Department of Cardiac, Thoracic and Vascular Sciences, University of Padua, Padua, Italy.
University of Chicago Medical Center, Chicago, Illinois.
J Am Soc Echocardiogr. 2018 Nov;31(11):1221-1228. doi: 10.1016/j.echo.2018.07.016. Epub 2018 Sep 8.
Left atrial (LA) longitudinal strain is a novel parameter used for the evaluation of LA function, with demonstrated prognostic value in several cardiac diseases. However, the extent of load dependency of LA strain is not well known. The aim of this study was to evaluate the impact of acute changes in preload on LA strain, side by side with LA volume, in normal subjects.
Twenty-five healthy volunteers (13 men; mean age, 31 ± 2 years) were prospectively enrolled, who underwent two-dimensional and three-dimensional echocardiographic imaging during acute stepwise reductions in preload using a tilt maneuver: baseline at 0°, followed by 40° and 80°. Left ventricular and LA size and function parameters were measured using standard methodology, and LA strain-time curves were obtained using speckle-tracking software (TomTec), resulting in reservoir, conduit, and contractile strain components. All parameters were compared among the three loading conditions using one-way analysis of variance for repeated measurements.
Although there were no significant changes in blood pressure, heart rate increased significantly with tilt. As expected, LA volumes, left ventricular volumes, and left ventricular ejection fraction, as well as E wave, A wave, and e' significantly decreased with progressive inclination. In parallel, LA reservoir, conduit, and contractile strain values decreased with reduction in preload (reservoir: 42.9 ± 3.9% to 27.5 ± 3.8%, P < .001; conduit: 29.3 ± 2.7% to 20.2 ± 5.0%, P < .001; contractile: 13.6 ± 2.9% to 7.3 ± 3.5%, P < .001). Paired post hoc analysis showed that all LA strain values were significantly different among all three tilt phases. Of note, percentage change in LA reservoir strain was significantly smaller than that in LA maximum volume.
In normal subjects, LA strain is preload dependent but to a lesser degree than LA volume. This difference underscores the relative advantage of LA strain over maximum volume, when LA assessment is used as part of the diagnostic paradigm.
左心房（LA）纵向应变是一种用于评估 LA 功能的新型参数，在几种心脏疾病中具有明显的预后价值。然而，LA 应变的负荷依赖性程度尚不清楚。本研究旨在评估正常受试者中前负荷急性变化对 LA 应变的影响，与 LA 容积并排进行。
前瞻性纳入 25 名健康志愿者（男 13 名；平均年龄 31±2 岁），通过倾斜试验在急性逐步降低前负荷时进行二维和三维超声心动图成像：基线 0°，然后是 40°和 80°。使用标准方法测量左心室和 LA 大小和功能参数，并使用斑点追踪软件（TomTec）获得 LA 应变时间曲线，得到储器、传导和收缩应变分量。使用重复测量的单向方差分析比较三种加载条件下的所有参数。
尽管血压没有明显变化，但倾斜时心率显著增加。如预期的那样，随着倾斜度的增加，LA 容积、左心室容积和左心室射血分数以及 E 波、A 波和 e'均显著降低。同时，LA 储器、传导和收缩应变值随着前负荷的降低而降低（储器：42.9±3.9%至 27.5±3.8%，P<.001；传导：29.3±2.7%至 20.2±5.0%，P<.001；收缩：13.6±2.9%至 7.3±3.5%，P<.001）。配对事后分析显示，所有 LA 应变值在所有三个倾斜阶段均有显著差异。值得注意的是，LA 储器应变的百分比变化明显小于 LA 最大容积的变化。
在正常受试者中，LA 应变是前负荷依赖性的，但程度小于 LA 容积。这种差异突出了 LA 应变相对于最大容积的相对优势，当 LA 评估作为诊断范式的一部分时。
