Key result
Beta-blocker therapy is linked to ~41% less exercise work-rate decline in stable CAD.
Why the study?
Exercise prescription based on fixed heart rate does not associate with a specific work rate during prolonged exercise, a phenomenon never evaluated in cardiac patients that might involve beta-adrenergic activity.
Does ongoing beta-blocker therapy attenuate the decrease in work rate during exercise at a constant submaximal heart rate in patients with stable coronary artery disease?
Observational (n=17)
No
Does ongoing beta-blocker therapy attenuate the decrease in work rate during exercise at a constant submaximal heart rate in patients with stable coronary artery disease?
Absolute Event Rate: -16% vs -27%
p-value: p=0.04
Beta-blockers attenuate the progressive decrease in work rate required to maintain a constant submaximal heart rate during exercise, suggesting that exercise prescription based on fixed heart rates may be inaccurate, particularly for patients not on beta-blockers.
Beta-blocker use was associated with less work rate decline during heart rate-clamped exercise in stable CAD; leaves open effects on training prescription or responses.
PURPOSE: Exercise prescription based on fixed heart rate (HR) values is not associated with a specific work rate (WR) during prolonged exercise. This phenomenon has never been evaluated in cardiac patients and might be associated with a slow component of HR kinetics and β-adrenergic activity. The aims were to quantify, in cardiac patients, the WR decrease at a fixed HR and to test if it would be attenuated by β-blockers. METHODS: Seventeen patients with coronary artery disease in stable conditions (69 ± 9 yr) were divided into two groups according to the presence (BB) or absence (no-BB) of a therapy with β-blockers, and performed on a cycle ergometer: an incremental exercise (INCR) and a 15-min "HR CLAMPED " exercise, in which WR was continuously adjusted to maintain a constant HR, corresponding to the gas exchange threshold +15%. HR was determined by the ECG signal, and pulmonary gas exchange was assessed breath-by-breath. RESULTS: During INCR, HR peak was lower in BB versus no-BB ( P < 0.05), whereas no differences were observed for other variables. During HR CLAMPED , the decrease in WR needed to maintain HR constant was less pronounced in BB versus no-BB (-16% ± 10% vs -27 ± 10, P = 0.04) and was accompanied by a decreased V̇O 2 only in no-BB (-13% ± 6%, P < 0.001). CONCLUSIONS: The decrease in WR during a 15-min exercise at a fixed HR (slightly higher than that at gas exchange threshold) was attenuated in BB, suggesting a potential role by β-adrenergic stimulation. The phenomenon may represent, also in this population, a sign of impaired exercise tolerance and interferes with aerobic exercise prescription.
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Baldassarre et al. (2023) conducted an observational in Coronary artery disease (n=17). Beta-blockers vs. No beta-blockers was evaluated on Decrease in work rate needed to maintain a constant heart rate (p=0.04). In patients with stable coronary artery disease, ongoing beta-blocker therapy significantly attenuated the decrease in work rate required to maintain a constant submaximal heart rate during a 15-minute exercise (-16% vs -27%, P=0.04).
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