Key result
β1-blocker treatment, but not αβ-blocker treatment, significantly predicted lower metabolic chronotropic relationship at anaerobic threshold (β = -0.432, p < 0.001) in subacute MI patients.
Why the study?
Simplified substitutes for heart rate at anaerobic threshold are difficult to use in subacute myocardial infarction patients on beta-blockers, prompting evaluation of how different beta-blocker types affect exercise heart rate response.
Does αβ-blocker treatment compared to β1-blocker treatment affect heart rate response during incremental cardiopulmonary exercise in Japanese male patients with subacute myocardial infarction?
Cohort (n=131)
Does αβ-blocker treatment compared to β1-blocker treatment affect heart rate response during incremental cardiopulmonary exercise in Japanese male patients with subacute myocardial infarction?
Effect estimate: β = -0.432
p-value: p=<0.001
Different types of beta-blockers (αβ vs β1) distinctly affect heart rate response during exercise in post-MI patients, necessitating adjustments when prescribing exercise intensity using simplified heart rate methods.
β1-blockers may blunt chronotropic response during exercise post-MI; leaves open whether αβ-blockers preserve it better than β1-selective agents.
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.
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Nemoto et al. (2019) conducted a cohort in Subacute myocardial infarction (n=131). αβ-blocker treatment vs. β1-blocker and no-β-blocker was evaluated on Metabolic chronotropic relationship (MCR) at anaerobic threshold (MCR-AT) and peak exercise (MCR-peak) (β = -0.432, p=<0.001). β1-blocker treatment, but not αβ-blocker treatment, significantly predicted lower metabolic chronotropic relationship at anaerobic threshold (β = -0.432, p < 0.001) in subacute MI patients.
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