Background: Impaired aerobic capacity in cardiac amyloidosis patients may be related to limited inotropic myocardial reserve and heart rate (HR) response limiting cardiac output rise. This study sought to investigate whether chronotropic incompetence (CI) and blunted HR recovery would be prevalent in patients with mutant transthyretin (ATTRv) cardiomyopathy.

Methods and results: Eighteen ATTRv (Val122Ile) patients (72 ± 8-year) and 15 age-matched controls (73 ± 3-year) were prospectively enrolled. Patients' medical records, pulmonary function and cardiopulmonary exercise testing, including non-invasive cardiac hemodynamics and chronotropic response were studied. Compared with age-matched controls, maximal workload (91 ± 8 vs. 65 ± 20 watts) and peak VO₂ (19.5 ± 3.0 vs. 14.4 ± 4.1 mL.kg⁻¹.min⁻¹) were lower in ATTRv patients. Despite reaching similar age-predicted maximal HR, ATTRv patients displayed smaller changes in stroke volume (SV) index relative to change in VO₂ (49 ± 26 vs. 67 ± 18%). Adequate chronotropic-metabolic index was prevalent in ATTRv patients. HR recovery, as percent decrease in peak HR at 1 and 3-min, was blunded ATTv patients.

Conclusions: In Val122Ile ATTRv patients, chronotropic response was appropriate relative to exercise intensity with only few patients displaying CI. HR response to exercise was further characterised by blunted HR recovery in ATTRv patients suggesting lower parasympathetic activity and greater sympathetic stimulation compared with controls.

背景：心脏淀粉样变性患者的有氧能力受损可能与正性肌力储备不足和心率（HR）反应限制心输出量升高有关。这项研究试图调查在患有变应运甲状腺素蛋白（ATTRv）心肌病的患者中是否普遍存在变时功能不佳（CI）和钝化的HR恢复。

方法和结果：前瞻性纳入了18例ATTRv（Val122Ile）患者（72±8岁）和15名年龄匹配的对照组（73±3岁）。研究了患者的病历，肺功能和心肺运动测试，包括非侵入性心脏血液动力学和变时反应。与年龄匹配的对照组相比，ATTRv患者的最大工作量（91±8 vs. 65±20瓦）和峰值VO ₂（19.5±3.0 vs. 14.4±4.1 mL.kg ^-1 .min ^-1）更低。尽管达到了年龄预测的最大HR，但ATTRv患者相对于VO _2的变化，其卒中体积（SV）指数的变化较小（49±26 vs. VO2）。67±18％）。足量的变时代谢指数在ATTRv患者中普遍存在。ATTv患者多为1分钟和3分钟时HR峰值降低百分比所致的HR恢复。

结论：在Val122Ile ATTRv患者中，相对于运动强度，变时反应是适当的，只有少数患者显示CI。HR对运动的反应的特征还在于，ATTRv患者的HR恢复减弱，提示与对照组相比，副交感神经活动较低，交感神经刺激较大。