超声心动图斜坡试验在左心室辅助装置连续血流中的应用：负荷条件是否重要？
Echocardiographic Ramp test for continuous-flow left ventricular assist devices: do loading conditions matter?
机构信息
Department of Medicine, Cardiovascular Division, University of Minnesota, Minneapolis, Minnesota.
Department of Medicine, Cardiovascular Division, University of Minnesota, Minneapolis, Minnesota.
出版信息
JACC Heart Fail. 2015 Apr;3(4):291-9. doi: 10.1016/j.jchf.2014.11.006. Epub 2015 Mar 11.
OBJECTIVES
This study investigated whether continuous AI and/or elevated mean arterial pressure (MAP) were associated with false positive results for flow obstruction in echocardiographic ramp speed tests in patients with a continuous-flow left ventricular assist device.
BACKGROUND
Failure to reduce the left ventricular end-diastolic diameter (LVEDD) with increasing device speeds in a ramp test is predictive of pump obstruction. Aortic insufficiency (AI) or increased MAP can diminish the ability to unload the left ventricle.
METHODS
LVEDD was plotted against device speed, and a linear function slope was calculated. A flat LVEDD slope (≥-0.16) was considered abnormal (suggestive of obstruction). Ramp test results were compared in patients with or without either AI or increased MAP at baseline speed, and receiver-operator characteristic (ROC) curves were constructed for predictors of device obstruction. Device thrombosis was confirmed by direct visualization of clot at explantation or on inspection by the manufacturer.
RESULTS
Of 78 ramp tests (55 patients), 36 were abnormal (18 true positive, 18 false positive), and 42 were normal (37 true negative, 5 false negative). In patients with AI, LVEDD slope was -0.14 ± 0.17, which was consistent with device obstruction (vs. -0.25 ± 0.11 in patients without AI; p < 0.001), despite no difference in mean lactate dehydrogenase concentration between the 2 groups (1,301 ± 1,651 U/l vs. 1,354 ± 1,365 U/l; p = 0.91). Area under the ROC curve (AUC) for LVEDD slope was 0.76 and improved to 0.88 after removal of patients with AI from the study. LVEDD slope in patients with MAP ≥85 mm Hg was similar to that for device obstruction (-0.18 ± 0.07) and was abnormal in 6 of the 12 ramp tests performed. Combining LVEDD slope with lactate dehydrogenase concentration increased the AUC to 0.96 as an indicator of device obstruction.
CONCLUSIONS
Abnormal loading conditions due to AI or elevated MAP may result in false positive ramp tests.
目的
本研究旨在探讨在接受连续血流左心室辅助装置（LVAD）的患者中，连续 AI 和/或平均动脉压（MAP）升高是否与超声心动图 ramp 速度试验中出现的血流阻塞假阳性结果相关。
背景
在 ramp 试验中，随着装置速度的增加，左心室舒张末期直径（LVEDD）未能降低是泵阻塞的预测因素。主动脉瓣关闭不全（AI）或 MAP 升高会降低左心室卸载的能力。
方法
LVEDD 与装置速度作图，并计算线性函数斜率。LVEDD 斜率平坦（≥-0.16）被认为异常（提示阻塞）。比较基线速度时伴有或不伴有 AI 或 MAP 升高的患者的 ramp 试验结果，并构建预测装置阻塞的受试者工作特征（ROC）曲线。通过直接观察血栓或制造商检查来确认装置血栓形成。
结果
在 78 次 ramp 试验（55 例患者）中，36 次异常（18 次真阳性，18 次假阳性），42 次正常（37 次真阴性，5 次假阴性）。在 AI 患者中，LVEDD 斜率为-0.14 ± 0.17，与装置阻塞一致（与无 AI 患者相比为-0.25 ± 0.11；p < 0.001），尽管两组间平均乳酸脱氢酶浓度无差异（1,301 ± 1,651 U/l 与 1,354 ± 1,365 U/l；p = 0.91）。LVEDD 斜率的 ROC 曲线下面积（AUC）为 0.76，在排除 AI 患者后，AUC 提高至 0.88。MAP≥85mm Hg 的患者的 LVEDD 斜率与装置阻塞相似（-0.18 ± 0.07），并且在进行的 12 次 ramp 试验中有 6 次异常。将 LVEDD 斜率与乳酸脱氢酶浓度相结合，可将 AUC 提高至 0.96，作为装置阻塞的指标。
结论
AI 或 MAP 升高导致的异常负荷条件可能导致 ramp 试验出现假阳性。
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