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_biplane) and compared with LVOTA calculated using the circular assumption (LVOTA_circ). In a subset of patients who underwent cardiac computed tomography, direct planimetry of LVOTA was used as a reference standard.

Results

LVOTA_biplane was significantly larger than LVOTA_circ (4.20 cm² [interquartile range, 3.66–4.90 cm²] vs 3.73 cm² [interquartile range, 3.14–4.15 cm²], P < .001). Among 30 patients who underwent cardiac computed tomography, LVOTA_biplane had better agreement with LVOTA by direct planimetry than LVOTA_circ (mean bias, −0.45 ± 0.63 vs −1.02 ± 0.63 cm²; P < .0001). Of 82 patients with severe AS (AVA ≤ 1 cm² using LVOTA_circ), 40 (49%) had discordant mean gradient (<40 mm Hg). By using LVOTA_biplane, 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.

中文翻译：

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通过同时双平面成像直接测量左心室流出道区域：挑战在评估主动脉瓣狭窄时对左心室流出道圆形假设的需求

背景

评估主动脉瓣狭窄 (AS) 需要计算主动脉瓣面积 (AVA)，这依赖于圆形左心室流出道 (LVOT) 的假设。然而，LVOT 往往是椭圆形的，圆形假设低估了真实的 LVOT 面积（LVOTA）。使用经胸超声心动图的双平面成像允许直接测量 LVOTA。本研究的目的是评估使用该技术获得 LVOTA 的可行性及其对 AS 分级中 AVA 与梯度标准不一致的影响。

方法

我们前瞻性研究了 134 名 AS 患者（中位年龄为 80 岁；四分位距为 73-87 岁；39% 为女性），其中 82 名 (61%) 为重度 AS，52 名 (39%) 为轻度或中度 AS。LVOTA 使用直接平面测量法（LVOTA_双平面）进行追踪，并与使用圆形假设（LVOTA _circ）计算的 LVOTA 进行比较。在接受心脏计算机断层扫描的一部分患者中，LVOTA 的直接面积测量被用作参考标准。

结果

LVOTA_双平面明显大于 LVOTA _circ（4.20 cm ² [四分位距，3.66–4.90 cm ² ] vs 3.73 cm ² [四分位距，3.14–4.15 cm ² ]，P  < .001）。在接受心脏计算机断层扫描的 30 名患者中，LVOTA_双平面通过直接面积测量法与 LVOTA 的一致性优于 LVOTA _circ（平均偏差，-0.45 ± 0.63 vs -1.02 ± 0.63 cm ²；P  < .0001）。在 82 名重度 AS（AVA ≤ 1 cm ²使用 LVOTA _circ）患者中，40 名 (49%) 的平均梯度不一致 (<40 mm Hg)。通过使用 LVOTA_双翼飞机，AVA 和平均梯度不一致的患者从 49% 下降到 27% ( P  = .004)，29% 的重度 AS 患者被重新分类为中度 AS，在低梯度 AS 组中重新分类的百分比最高保留左心室射血分数。

结论

使用双平面成像的直接面积测量避免了使用圆形假设对 LVOTA 的固有低估。通过双平面测量法获得的 LVOTA 可以使 AVA 与平均梯度和 AS 严重程度分类之间更好地一致。