Key result
Optimized beta-blocker therapy in heart failure patients demonstrated a reliable relationship between oxygen consumption and heart rate reserves (slope 0.986) versus non-optimized therapy (slope 0.030).
Why the study?
Does optimized beta-blocker therapy improve the reliability of the relationship between heart rate reserve and oxygen uptake reserve during exercise in heart failure patients?
Observational (n=62)
Does optimized beta-blocker therapy improve the reliability of the relationship between heart rate reserve and oxygen uptake reserve during exercise in heart failure patients?
Absolute Event Rate: 0.986% vs 0.03%
The relationship between heart rate reserve and oxygen uptake reserve during exercise is reliable in heart failure patients on optimized beta-blocker therapy, but unreliable in those on non-optimized therapy.
Optimized beta-blocker therapy was associated with reliable HR-O2 reserve coupling in HF; hypothesis-generating, needs randomized confirmation.
BACKGROUND: The relationship between the percentage of oxygen consumption reserve and percentage of heart rate reserve in heart failure patients either on non-optimized or off beta-blocker therapy is known to be unreliable. The aim of this study was to evaluate the relationship between the percentage of oxygen consumption reserve and percentage of heart rate reserve in heart failure patients receiving optimized and non-optimized beta-blocker treatment during a treadmill cardiopulmonary exercise test. METHODS: A total of 27 sedentary heart failure patients (86% male, 50+/-12 years) on optimized beta-blocker therapy with a left ventricle ejection fraction of 33+/-8% and 35 sedentary non-optimized heart failure patients (75% male, 47+/-10 years) with a left ventricle ejection fraction of 30+/-10% underwent the treadmill cardiopulmonary exercise test (Naughton protocol). Resting and peak effort values of both the percentage of oxygen consumption reserve and percentage of heart rate reserve were, by definition, 0 and 100, respectively. RESULTS: The heart rate slope for the non-optimized group was derived from the points 0.949+/-0.088 (0 intercept) and 1.055+/-0.128 (1 intercept), p<0.0001. The heart rate slope for the optimized group was derived from the points 1.026+/-0.108 (0 intercept) and 1.012+/-0.108 (1 intercept), p=0.47. Regression linear plots for the heart rate slope for each patient in the non-optimized and optimized groups revealed a slope of 0.986 (almost perfect) for the optimized group, but the regression analysis for the non-optimized group was 0.030 (far from perfect, which occurs at 1). CONCLUSION: The relationship between the percentage of oxygen consumption reserve and percentage of heart rate reserve in patients on optimized beta-blocker therapy was reliable, but this relationship was unreliable in non-optimized heart failure patients.
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Carvalho et al. (2008) conducted an observational in Heart failure (n=62). Optimized beta-blocker therapy vs. Non-optimized beta-blocker therapy was evaluated on Relationship between the percentage of oxygen consumption reserve and percentage of heart rate reserve. Optimized beta-blocker therapy in heart failure patients demonstrated a reliable relationship between oxygen consumption and heart rate reserves (slope 0.986) versus non-optimized therapy (slope 0.030).
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