Aims In patients with severe aortic stenosis (AS) and preserved left ventricular ejection fraction (LVEF), low flow (LF) is currently defined using Doppler-echocardiography by a stroke volume index (SVi)<35 mL/m2. However, the relationship between LF and outcome remains unclear as data on normal reference values defining LF are scarce, and previous studies did not explore the risk associated with other SVi cut-points. We analysed the relationship between LF and mortality in severe AS to establish prognostic LF values associated with mortality risk. Methods and results This study included 1450 consecutive patients with severe AS (aortic valve area <1 cm2 and/or <0.6 cm2/m2) and preserved LVEF and 1645 controls with normal echocardiograms. Patients were stratified in three groups: (i) SVi > 35 mL/m2 or SV > 70 mL; (ii) SVi 30-35 mL/m2 or SV 55-70 mL; and (iii) SVi < 30 mL/m2 or SV < 55 mL. Mortality with medical and surgical management was analysed. Five-year survival was low for SVi < 30 mL/m2 and SV < 55 mL compared to the other groups (all P-values <0.001). After adjustment for outcome predictors, including aortic valve replacement, mortality risk was considerable with SVi < 30 mL/m2 vs. >35 mL/m2 [adjusted hazard ratio (HR) 1.60 (1.17-2.18)] and SV < 55 mL vs. >70 mL [adjusted HR 1.84 (1.32-2.58)]. Similar mortality risk was observed for SVi 30-35 mL/m2 vs. >35 mL/m2 [adjusted HR 1.05 (0.78-1.41)], and for SV 55-70 mL vs. >70 mL [adjusted HR 1.22 (0.94-1.58)]. The prognostic impact of SVi < 30 mL/m2 and SV < 55 mL was consistent in subgroups, including asymptomatic patients and patients with low-gradient severe AS. Conclusion Low flow defined as SVi < 30 mL/m2 or SV < 55 mL is an important outcome predictor in severe AS with preserved LVEF under medical and surgical management. Further studies are needed to prospectively test these values for risk stratification and decision making.

中文翻译：

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低每搏输出量对重度主动脉瓣狭窄和左心室射血分数保留患者死亡率的影响

目的 在严重主动脉瓣狭窄 (AS) 和左心室射血分数 (LVEF) 保留的患者中，目前使用多普勒超声心动图通过每搏量指数 (SVi) < 35 mL/m2 来定义低流量 (LF)。然而，LF 与结果之间的关系仍不清楚，因为定义 LF 的正常参考值的数据很少，而且以前的研究没有探讨与其他 SVi 切点相关的风险。我们分析了严重 AS 中 LF 与死亡率之间的关系，以确定与死亡风险相关的预后 LF 值。方法和结果 本研究包括 1450 名重度 AS（主动脉瓣面积 <1 cm2 和/或 <0.6 cm2/m2）且保留 LVEF 的连续患者和 1645 名超声心动图正常的对照患者。患者分为三组：(i) SVi > 35 mL/m2 或 SV > 70 mL；(ii) SVi 30-35 mL/m2 或 SV 55-70 mL；(iii) SVi < 30 mL/m2 或 SV < 55 mL。分析了内科和外科管理的死亡率。与其他组相比，SVi < 30 mL/m2 和 SV < 55 mL 的五年生存率较低（所有 P 值 <0.001）。在调整结果预测因子（包括主动脉瓣置换术）后，SVi < 30 mL/m2 vs. >35 mL/m2 [调整后的风险比 (HR) 1.60 (1.17-2.18)] 和 SV < 55 mL vs. >70 mL [调整后的 HR 1.84 (1.32-2.58)]。观察到 SVi 30-35 mL/m2 与 >35 mL/m2 [调整后的 HR 1.05 (0.78-1.41)] 以及 SV 55-70 mL 与 >70 mL [调整后的 HR 1.22 (0.94- 1.58)]。SVi < 30 mL/m2 和 SV < 55 mL 的预后影响在亚组中是一致的，包括无症状患者和低梯度重度 AS 患者。结论 定义为 SVi < 30 mL/m2 或 SV < 55 mL 的低流量是内科和手术治疗下 LVEF 保留的重度 AS 的重要预后预测因子。需要进一步的研究来前瞻性地测试这些值以进行风险分层和决策。