Effects of αβ-Blocker Versus β1-Blocker Treatment on Heart Rate Response During Incremental Cardiopulmonary Exercise in Japanese Male Patients with Subacute Myocardial Infarction.

Shinji Nemoto,Atsuhiko Matsunaga,Yoshihiro J Akashi,Kazuto Omiya,Kazuhiro P Izawa,Kentaro Kamiya,Kazuya Yoshizawa,Yusuke Kasahara,Naoya Takeichi,Norio Suzuki,Satoshi Watanabe

doi:10.3390/ijerph16162838

Abstract

A simplified substitute for heart rate (HR) at the anaerobic threshold (AT), i.e., resting HR plus 30 beats per minute or a percentage of predicted maximum HR, is used as a way to determine exercise intensity without cardiopulmonary exercise testing (CPX) data. However, difficulties arise when using this method in subacute myocardial infarction (MI) patients undergoing beta-blocker therapy. This study compared the effects of αβ-blocker and β1-blocker treatment to clarify how different beta blockers affect HR response during incremental exercise. MI patients were divided into αβ-blocker (n = 67), β1-blocker (n = 17), and no-β-blocker (n = 47) groups. All patients underwent CPX one month after MI onset. The metabolic chronotropic relationship (MCR) was calculated as an indicator of HR response from the ratio of estimated HR to measured HR at AT (MCR-AT) and peak exercise (MCR-peak). MCR-AT and MCR-peak were significantly higher in the αβ-blocker group than in the β1-blocker group (p < 0.001, respectively). Multiple regression analysis revealed that β1-blocker but not αβ-blocker treatment significantly predicted lower MCR-AT and MCR-peak (β = −0.432, p < 0.001; β = −0.473, p < 0.001, respectively). Based on these results, when using the simplified method, exercise intensity should be prescribed according to the type of beta blocker used.

Highlights

Many guidelines recommend exercise training for patients with myocardial infarction (MI) [1,2]because exercise training has been associated with reduced cardiovascular mortality after acute MI [3].Int
These results suggest that the negative chronotropic effect of beta blockers during incremental cardiopulmonary exercise testing (CPX) may be stronger with β1-blockers than with αβ-blockers in subacute MI patients
The values of metabolic chronotropic relationship (MCR)-anaerobic threshold (AT) and MCR-peak were 0.85 ± 0.07 and 0.90 ± 0.08, respectively, in the αβ-blocker group, and 0.77 ± 0.07 and 0.78 ± 0.11, respectively, in the β1-blocker group. These results show that the β1-blocker group had a low chronotropic index, while the αβ-blocker group did not, suggesting that the effect of β1-blockers decreasing heart rate (HR) response during incremental CPX may be stronger than with αβ-blockers

Summary

Methods

A total of 665 consecutive acute MI patients underwent cardiac rehabilitation at St. Marianna. 297 were able to undergo symptom-limited CPX one month after the onset of MI, and 131 who did not meet the following exclusion criteria were enrolled in this retrospective cross-sectional study: the presence of atrial fibrillation, complex arrhythmia, or pacemaker; recent myocardial infarction; history of cardiac surgery; female sex; maximum respiratory exchange ratio (RER) during CPX < 1.10; and use of drugs other than beta blockers with positive or negative chronotropic effects (e.g., verapamil, diltiazem hydrochloride). Patients were divided into the following three groups according to the type of beta blocker used: the αβ-blocker group (67 patients), the β1-blocker group (17 patients), and the no-β-blocker group (47 patients). All patients were clinically stable and were examined while being treated with stable doses of medication

Results

Discussion

Conclusion