Purpose: 

It is recommended that patients with myocardial infarction (MI) be prescribed exercise by target heart rate (HR) at the anaerobic threshold (AT) via cardiopulmonary exercise testing (CPX). Although percent HR reserve using predicted HR_max (%HRR_pred) is used to prescribe exercise if CPX or an exercise test cannot be performed, %HRR_pred is especially difficult to use when patients take β-blockers. We devised a new formula to predict HR at AT (HR_AT) that considers β-blocker effects in MI patients and validated its accuracy.

Methods: 

The new formula was created using the data of 196 MI patients in our hospital (derivation sample), and its accuracy was assessed using the data of 71 MI patients in other hospitals (validation sample). All patients underwent CPX 1 mo after MI onset, and resting HR, resting systolic blood pressure (SBP), and HR_AT were measured during CPX.

Results: 

The results of multiple regression analysis in the derivation sample gave the following formula (R² = 0.605, P < .001): predicted HR_AT = 2.035 × (≥65 yr:−1, <65 yr:1) + 3.648 × (body mass index <18.5 kg/m²:−1, body mass index ≥18.5 kg/m²:1) + 4.284 × (β1-blocker(+):−1, β1-blocker(−):1) + 0.734 × (HR_rest) + 0.078 × (SBP_rest) + 36.812. This formula consists entirely of predictors that can be obtained at rest. HR_AT and predicted HR_AT with the new formula were not significantly different in the validation sample (mean absolute error: 5.5 ± 4.1 bpm).

Conclusions: 

The accuracy of the new formula appeared to be favorable. This new formula may be a practical method for exercise prescription in MI patients, regardless of their β-blocker treatment status, if CPX is unavailable.

中文翻译：

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考虑β受体阻滞剂对心肌梗死患者影响的预测无氧阈值心率的新公式：多机构回顾性横断面研究

目的： 

建议心肌梗死(MI) 患者通过心肺运动测试 (CPX) 根据无氧阈 (AT) 下的目标心率 (HR) 进行运动。尽管在无法进行 CPX 或运动测试的情况下，使用预测 HR _max (%HRR _pred ) 的 HR 储备百分比可用于制定运动处方，但当患者服用 β 受体阻滞剂时，%HRR _pred特别难以使用。我们设计了一个新的公式来预测 AT 心率 (HR _AT )，该公式考虑了 β 受体阻滞剂对 MI 患者的影响，并验证了其准确性。

方法： 

新公式是利用我院196例心梗患者的数据（推导样本）创建的，并利用其他医院71例心梗患者的数据（验证样本）评估其准确性。所有患者在 MI 发病后 1 个月接受 CPX，并在 CPX 期间测量静息 HR、静息收缩压 (SBP) 和 HR _{AT 。}

结果： 

推导样本的多元回归分析结果给出以下公式（R ² = 0.605，P < .001）： 预测 HR _AT = 2.035 ×（≥65 yr:−1，<65 yr:1）+ 3.648 ×（体重指数<18.5 kg/m ² :−1，体重指数≥18.5 kg/m ² :1) + 4.284 × ( β 1-阻滞剂(+):−1, β 1-阻滞剂(−):1) + 0.734 ×（心率_休息）+ 0.078 ×（收缩压_休息）+ 36.812。该公式完全由可以在静止状态下获得的预测变量组成。验证样本中的HR _AT和使用新公式预测的 HR _{AT没有显着差异（平均绝对误差：5.5 ± 4.1 bpm）。}

结论： 

新公式的准确性似乎不错。如果 CPX 不可用，无论患者的 β 受体阻滞剂治疗状况如何，这种新公式可能是 MI 患者运动处方的实用方法。