Clark A L, Coats A J
Department of Cardiac Medicine, National Heart and Lung Institute, London, UK.
Int J Cardiol. 1995 May;49(3):225-31. doi: 10.1016/0167-5273(95)02316-o.
The exercise limitation of patients with chronic heart failure may be due in part to an inability to increase heart rate as normal, a limitation sometimes referred to as chronotropic incompetence. This may be due to down regulation of beta receptors.
Fifty-seven patients with chronic heart failure and 14 age-matched controls underwent symptom limited treadmill exercise tests with metabolic gas exchange measurements. Heart rate and blood pressure responses were also recorded.
Peak oxygen consumption was reduced in the heart failure patients (19.6 (S.D. +/- 7.6) vs. 35.0 (+/- 9.9); P < 0.001). Heart rate at peak exercise (r = 0.47, P < 0.001), and change in heart rate from rest to peak exercise (r = 0.59; P < 0.001) and rate pressure product at peak exercise (r = 0.56, P < 0.001) all correlated with peak oxygen consumption. The percentage of predicted maximal heart rate at peak exercise correlated poorly with peak oxygen consumption (r = 0.29; P > 0.05). Peak systolic and diastolic blood pressures did not correlate with peak oxygen consumption. Sixteen patients had chronotropic incompetence. There was no significant difference between this group and those without chronotropic incompetence in the intensity of exercise performed, underlying diagnosis, drug therapy or prevalence of atrial fibrillation. There was a trend towards shorter exercise times in the incompetent group (430 (+/- 251) vs. 545 (+/- 216) s; P = 0.08) compared to the other patients.
Chronotropic incompetence was seen in < 30% of patients with chronic heart failure. However, there are few differences between the group with chronotropic incompetence and the group without. Chronotropic incompetence is thus unlikely to be a major factor limiting exercise capacity in unselected patients with chronic heart failure and is likely to be the major factor limiting exercise in a much smaller proportion of patients.
慢性心力衰竭患者运动受限可能部分归因于无法像正常人一样增加心率，这种限制有时被称为变时性功能不全。这可能是由于β受体下调所致。
57例慢性心力衰竭患者和14例年龄匹配的对照者接受了症状限制性平板运动试验，并测量了代谢气体交换。同时记录心率和血压反应。
心力衰竭患者的峰值耗氧量降低（19.6（标准差±7.6）对35.0（±9.9）；P<0.001）。运动峰值时的心率（r = 0.47，P<0.001）、从静息到运动峰值时的心率变化（r = 0.59；P<0.001）以及运动峰值时的心率血压乘积（r = 0.56，P<0.001）均与峰值耗氧量相关。运动峰值时预测最大心率的百分比与峰值耗氧量的相关性较差（r = 0.29；P>0.05）。收缩压和舒张压峰值与峰值耗氧量无关。1十六例患者存在变时性功能不全。该组与无变时性功能不全的患者在运动强度、基础诊断、药物治疗或房颤患病率方面无显著差异。与其他患者相比，变时性功能不全组的运动时间有缩短趋势（430（±251）对545（±216）秒；P = 0.08）。
在<30%的慢性心力衰竭患者中可见变时性功能不全。然而，变时性功能不全组和无变时性功能不全组之间几乎没有差异。因此，变时性功能不全不太可能是未选择的慢性心力衰竭患者运动能力受限的主要因素，而可能是在比例小得多的患者中限制运动的主要因素。
