左心室流出道面积的同步双平面成像直接测径法：质疑评估主动脉瓣狭窄时左心室流出道呈圆形假设的必要性。
Direct Planimetry of Left Ventricular Outflow Tract Area by Simultaneous Biplane Imaging: Challenging the Need for a Circular Assumption of the Left Ventricular Outflow Tract in the Assessment of Aortic Stenosis.
机构信息
Division of Cardiology, Cardiac Ultrasound Laboratory, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
出版信息
J Am Soc Echocardiogr. 2020 Apr;33(4):461-468. doi: 10.1016/j.echo.2019.12.002.
BACKGROUND
Evaluation of aortic stenosis (AS) requires calculation of aortic valve area (AVA), which relies on the assumption of a circular-shaped left ventricular outflow tract (LVOT). However, the LVOT is often elliptical, and the circular assumption underestimates the true LVOT area (LVOTA). Biplane imaging using transthoracic echocardiography allows direct planimetry of LVOTA. The aim of this study was to assess the feasibility of obtaining LVOTA using this technique and its impact on the discordance between AVA and gradient criteria in AS grading.
METHODS
We prospectively studied 134 patients (median age, 80 years; interquartile range, 73-87 years; 39% women) with AS, including 82 (61%) with severe AS and 52 (39%) with mild or moderate AS. LVOTA was traced using direct planimetry (LVOTA) and compared with LVOTA calculated using the circular assumption (LVOTA). In a subset of patients who underwent cardiac computed tomography, direct planimetry of LVOTA was used as a reference standard.
RESULTS
LVOTA was significantly larger than LVOTA (4.20 cm [interquartile range, 3.66-4.90 cm] vs 3.73 cm [interquartile range, 3.14-4.15 cm], P < .001). Among 30 patients who underwent cardiac computed tomography, LVOTA had better agreement with LVOTA by direct planimetry than LVOTA (mean bias, -0.45 ± 0.63 vs -1.02 ± 0.63 cm; P < .0001). Of 82 patients with severe AS (AVA ≤ 1 cm using LVOTA), 40 (49%) had discordant mean gradient (<40 mm Hg). By using LVOTA, patients with discordant AVA and mean gradient decreased from 49% to 27% (P = .004), and 29% of patients with severe AS were reclassified with moderate AS, with the highest percentage of reclassification in the group with low-gradient AS with preserved left ventricular ejection fraction.
CONCLUSIONS
Direct planimetry using biplane imaging avoids the inherent underestimation of LVOTA using the circular assumption. LVOTA obtained by biplane planimetry can lead to better concordance between AVA and mean gradient and classification of AS severity.
背景
主动脉瓣狭窄（AS）的评估需要计算主动脉瓣口面积（AVA），这依赖于左心室流出道（LVOT）呈圆形的假设。然而，LVOT 通常呈椭圆形，圆形假设会低估真实的 LVOT 面积（LVOTA）。经胸超声心动图的双平面成像可直接进行 LVOTA 的平面测量。本研究旨在评估使用该技术获得 LVOTA 的可行性及其对 AS 分级中 AVA 与梯度标准之间不匹配的影响。
方法
我们前瞻性研究了 134 例 AS 患者（中位年龄 80 岁；四分位距 73-87 岁；39%为女性），包括 82 例（61%）严重 AS 和 52 例（39%）轻度或中度 AS。使用直接平面测量法（LVOTA）追踪 LVOTA，并将其与使用圆形假设计算的 LVOTA（LVOTA）进行比较。在一部分接受心脏计算机断层扫描的患者中，使用直接平面测量法的 LVOTA 作为参考标准。
结果
LVOTA 明显大于 LVOTA（4.20cm[四分位距 3.66-4.90cm]比 3.73cm[四分位距 3.14-4.15cm]，P<0.001）。在 30 例接受心脏计算机断层扫描的患者中，LVOTA 通过直接平面测量法与 LVOTA 的一致性优于 LVOTA（平均偏差-0.45±0.63cm 比-1.02±0.63cm，P<0.0001）。在 82 例严重 AS 患者（LVOTA 为≤1cm2）中，40 例（49%）存在平均梯度不一致（<40mm Hg）。使用 LVOTA 后，AVA 和平均梯度不一致的患者从 49%降至 27%（P=0.004），29%的严重 AS 患者被重新分类为中度 AS，其中左心室射血分数保留的低梯度 AS 患者的重新分类比例最高。
结论
双平面成像的直接平面测量法可避免使用圆形假设时 LVOTA 的固有低估。双平面平面测量法获得的 LVOTA 可使 AVA 与平均梯度之间的一致性更好，并改善 AS 严重程度的分类。
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