From the Division of Cardiovascular Surgery, Peter Munk Cardiac Centre, University Health Network, University of Toronto.
Division of Nephrology, University Health Network, University of Toronto.
ASAIO J. 2020 Aug;66(8):875-880. doi: 10.1097/MAT.0000000000001082.
Continuous-flow left ventricular assist device (CF-LVAD) recipients exhibit impaired exercise capacity. Long-term continuous blood flow also elevates norepinephrine (NE) and aldosterone (Aldo) levels. However, the relationship between exercise capacity and neurohormonal activation has not been elucidated. Our study objective was to assess the association between cardiopulmonary exercise testing (CPT) measures and neurohormonal levels in CF-LVAD recipients. Symptom-limited CPT on a treadmill, using the modified Bruce protocol was performed in 15 CF-LVAD recipients. Norepinephrine and Aldo levels were measured, and the association between their levels and CPT measures were assessed. Peak VO2 (13.6 ml/kg/min) and percent age, sex predicted VO2 max (49.4%), and oxygen pulse (O2 pulse) (9.0 ± 4.0 ml/beat) were low, whereas minute ventilation/carbon dioxide output (VE/VCO2) slope (35) was elevated. In addition, VO2 at anaerobic threshold (VO2 AT), and O2 pulse values negatively correlated with NE levels. Norepinephrine levels positively correlated with chronotropic responses and heart rate (HR) recovery. Aldo levels in CF-LVAD recipients were not related to any CPT measures. Continuous-flow left ventricular assist device recipients exhibited impaired exercise capacity and chronotropic incompetence (CI). Despite the association of NE levels with chronotropic responses at peak exercise, neither NE levels nor chronotropic responses predicted peak VO2. This suggests that CI may not be the primary factor responsible for the low peak VO2. O2 pulse, which is a combined measure for stroke volume and peripheral oxygen extraction during exercise, was an independent predictor of peak VO2. Future studies should examine the contribution of peripheral factors to exercise capacity limitations.
持续流动左心室辅助装置（CF-LVAD）受者表现出运动能力受损。长期持续的血流也会升高去甲肾上腺素（NE）和醛固酮（Aldo）水平。然而，运动能力与神经激素激活之间的关系尚未阐明。我们的研究目的是评估 CF-LVAD 受者心肺运动测试（CPT）测量值与神经激素水平之间的关系。在跑步机上进行了 15 名 CF-LVAD 受者的症状限制 CPT，使用改良 Bruce 方案。测量了去甲肾上腺素和醛固酮水平，并评估了它们水平与 CPT 测量值之间的关系。峰值 VO2（13.6ml/kg/min）和占预测 VO2 最大值的百分比（49.4%）和氧脉冲（O2 脉冲）（9.0±4.0ml/beat）较低，而分钟通气量/二氧化碳输出（VE/VCO2）斜率（35）升高。此外，无氧阈（VO2 AT）时的 VO2 和 O2 脉冲值与 NE 水平呈负相关。去甲肾上腺素水平与变时反应和心率（HR）恢复呈正相关。CF-LVAD 受者的醛固酮水平与任何 CPT 测量值均无关。持续流动左心室辅助装置受者表现出运动能力受损和变时功能不全（CI）。尽管 NE 水平与峰值运动时的变时反应有关，但 NE 水平和变时反应均不能预测峰值 VO2。这表明 CI 可能不是导致峰值 VO2 降低的主要因素。O2 脉冲是运动期间每搏量和外周氧摄取的综合测量值，是峰值 VO2 的独立预测因子。未来的研究应该检查外周因素对运动能力受限的贡献。
