ABC | Volume 112, Nº3, March 2019

Brief Communication Beta-Blocker Type Effect on Substrate Oxidation during HIIE in Heart Failure Patients: Pilot Data Paula Aver Bretanha Ribeiro, 1,2, 3 Eve Normandin, 1,2,4 Philippe Meyer, 5 Martin Juneau, 1,2 Michel White, 1,2 Anil Nigam, 1,2 Mathieu Gayda 1,2 Cardiovascular Prevention and Rehabilitation Centre (ÉPIC), Montreal Heart Institute, 1 Montreal, Quebec – Canada Department of Medicine, Faculty of Medicine, University of Montreal, 2 Montreal, Quebec – Canada Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul (UFRS), 3 Porto Alegre, RS – Brazil Faculty of Physical Education and Sports, University of Sherbrooke, 4 Sherbrooke, Quebec – Canada Division of Cardiology, University Hospital, Faculty of Medicine, University of Geneva, 5 Geneva – Switzerland Keywords Heart Failure, Adrenergic beta-Antagonists; Stroke Volume, Chemical Oxidation, Exercise. Mailing Address: Paula Aver Bretanha Ribeiro • Cardiovascular Prevention and Rehabilitation Centre (ÉPIC), 5055 St Zotique East, Montreal, Quebec, H1T1N6, Canada E-mail: paulaabribeiro@gmail.com Manuscript received January 27, 2018, revised manuscript April 26, 2018, accepted August 15, 2018 DOI: 10.5935/abc.20190039 Abstract The effect of third and second-generation type of beta- blocker on substrate oxidation especially during high-intensity exercises are scarce. The objective of the study is to explore differences of beta-blocker regimens (vasodilating vs. non-vasodilating beta-blockers) for substrate oxidation during in high-intensity intermittent exercise (HIIE) in chronic heart failure and reduced ejection fraction (HFrEF). Eighteen CHF males (58.8 ± 9 years), 8 under use of β 1 specific beta-blockers+alfa 1-blocker and 10 using β 1 non‑specific beta-blockers, were randomly assigned to 4 different HIIE, in a cross-over design. The 4 protocols were: 30 seconds (A and B) or 90 seconds (C and D) at 100% peak power output, with passive (A and C) or active recovery (50% of PPO; B and D). Energy expenditure (EE; kcal/min), quantitative carbohydrate (CHO) and lipid oxidation (g/min) and qualitative (%) contribution were calculated. Two-way ANOVA and Bonferroni post-hoc test were used (p-value≤0.05) to compare CHO and lipid oxidation at rest and at 10min. Total exercise time or EE did not show differences for beta‑blocker use. The type of beta-blocker use showed impact in CHO (%) and lipid (g/min and %) for rest and 10 min, but absolute contribution of CHO (g/min) was different just at 10min (Interaction p = 0.029). Higher CHO oxidation was found in vasodilating beta-blockers when comparing to non-vasodilating. According to our pilot data, there is an effect of beta‑blocker type on substrate oxidation during HIIE, but no influence on EE or exercise total time in HFrEF patients. Introduction To reduce sympathetic nervous system activation and improve myocardium contractility, morbidity and mortality, most of the chronic heart failure (CHF) patients are under beta-blocker use. 1 Besides all benefits, there is some evidence showing reduced glycemic control, weight gain, insulin secretion inhibition and resistance and dyslipidemia in resting states in patients under beta-blocker regimen. 2,3 Also, it was showed that the use of beta blockers could remodel substrate use during moderate-intensity continuous exercise. 4 The third generation of beta-blockers, described as vasodilating β - blockers (i.e. β non-selective + α -1 blocker), seem to have a beneficial effect comparing to previous ones ( β –selective). Because of its lack of effect on α 1- adrenergic receptors, non-vasodilating beta blockers can induce vasoconstriction, reducing blood flow and glucose uptake at muscular level. 2,3 But when comparisons between carvedilol vs. metoprolol were made concerning NYHA no changes were found. 5 However, there is a lack of evidence of comparison of the type of beta-blocker during exercise, especially during high-intensity exercises (i. e. vasodilating vs. non-vasodilating). Regarding exercise intensity, there is an increasing use of high-intensity interval training programs in cardiac rehabilitation sites. Enough evidence is provided about the superior benefits of this modality for maximal oxygen uptake (VO 2 max) and quality of life when compared to moderate continuous training. 6 However, still a lack of evidence about different high-intensity interval exercise (HIIE) prescriptions in terms of optimal intensity, duration of bouts, recovery time and type (passive or active). 7 Also, not enough evidence about substrate utilization in cardiac rehabilitation context, especially what concerns to medication use. 4,8 We believe that vasodilating beta-blockers could especially influence carbohydrate (CHO) oxidation, and this may reflect in total time of exercise session. Therefore, for this study, we compared substrate oxidation, energy expenditure (EE) and total time of HIIE protocols performed by CHF with reduced left ejection fraction (HFrEF), under two different beta-blocker regimens (vasodilating vs. non-vasodilating). Methods Participants Twenty stable HFrEF were recruited from the heart failure ambulatory at the Montreal Heart Institute. This is a sub-study, inclusion criteria and exclusion criteria have been detailed in the previous publication, 7 and clinical information was 304