Editorial to ‘The effect of high-intensity interval training on exercise capacity in post-myocardial infarction patients: a systematic review and meta-analysis’

This editorial refers to ‘The effect of high-intensity interval training on exercise capacity in post-myocardial infarction patients: a systematic review and meta-analysis’ by Y. Qin et al. pp. 475--484.

The meta-analysis conducted by Qin et al.¹ explored the effect of high-intensity interval training (HIIT) on exercise capacity in 387 post-myocardial infarction patients. Authors found that, compared to moderate intensity continuous training (MICT) and routine physical activity, HIIT significantly improved exercise capacity as measured by peak oxygen consumption (peak VO₂: +3.83 mL/kg/min). These findings are in line with previous reports supporting the inclusion of HIIT in cardiac rehabilitation programs in different cohorts of patients as an adjunct or alternative modality to moderate-intensity exercise for stable patients.² In the Feasibility, Safety, Adherence, and Efficacy of High Intensity Interval Training in Rehabilitation for Coronary Heart Disease (FITR Heart Study), a randomized clinical trial including 96 patients with coronary artery disease attending cardiac rehabilitation, peak VO₂ increased by +2.9 mL/kg/min (+10%) with HIIT compared to +1.2 mL/kg/min (+4%) with MICT (P = 0.02).³ In a meta-analysis including data from a larger cohort (n = 446) of chronic heart failure patients, HIIT significantly improved exercise capacity (peak VO₂: +1.04 mL/kg/min) compared to MICT.⁴ Notably, these apparently modest training-induced changes in peak VO₂ are of great clinical meaning in cardiac patients. It has been previously demonstrated that, independent from the initial exercise capacity, an additional increase in exercise capacity by 1% after training would be associated with a decrease of 2% in cardiovascular mortality.⁵ However, whether starting HIIT programs early after index event (myocardial infarction) might translate into a prognostic advantage still remains to be elucidated.

In their meta-analysis, authors did not report significant differences in left ventricular end-diastolic volume and in left ventricular ejection fraction.¹ Several studies reported exercise-induced (MICT) favourable cardiac chambers remodelling in post-infarction^6–8 and in heart failure (either with reduced or preserved ejection fraction) patients.^9,10 However, the effect of HIIT on ventricular remodelling in post-infarction patients is scarcely reported.^11–13 Trachsel et al.¹² recently reported that HIIT was associated with favourable left ventricular (LV) remodelling as evaluated by global longitudinal strain, considered a more sensitive method for evaluating LV ejection performance in ischaemic heart disease.¹⁴

In their meta-analysis, authors did not evaluate the cardiometabolic effects of HIIT.¹ Recent reports suggested that supervised HIIT results in significant reductions in total fat mass and abdominal fat percentage and improved lipid profile in post-infarction patients undergoing CR.¹⁵ In addition, greater improvements in metabolic syndrome and body composition in post-infarction patients with metabolic syndrome undergoing CR have been reported.¹⁶ However, universal agreement on the most effective exercise prescription to improve metabolic syndrome for post-infarction patients remains unclear and future studies are encouraged in order to evaluate the potential benefits of high-volume training on cardiometabolic profile.

In their meta-analysis, authors reported no major safety issues.¹ These findings are in line with the consolidated evidence that exercise-based cardiac rehabilitation is safe in different patient’s populations;^17–20 although safety-related issues of HIIT in post-infarction patients require further evaluation.

An ‘optimum’ universally agreed exercise training program for post-infarction patients has not been yet delineated. In heart failure patients from the ARISTOS-HF trial,²¹ the combined model of training [aerobic training (AT)/resistance training (RT)/inspiratory muscle training (IMT), named ARIS training] demonstrated superior effects on peak VO₂ and LV dimensions compared to AT/RT, AT/IMT, or AT. Future trials are eagerly awaited in order to establish whether a combined training program initiated early after the acute event might confer a prognostic advantage in post-infarction patients. In addition, different exercise intensity domains should be reconsidered in the guidelines.^22,23

Conflict of interest: none declared.

The opinions expressed in this article are not necessarily those of the Editors of the European Journal of Preventive Cardiology or of the European Society of Cardiology.

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