ABC | Volume 110, Nº2, February 2018

Review Article Perrier-Melo et al Interval exercise in heart transplant recipients Arq Bras Cardiol. 2018; 110(2):188-194 Figure 1 – Flowchart of the search and selection process of the articles included in this review. Number of articles found (1064) 994 articles excluded for not meeting the selection criteria 70 eligible articles 53 duplicates 17 studies selected for qualitative analysis 14 articles excluded: 3 review articles, 3 case studies and 8 studies for not reporting on HIIT 3 studies included Regarding HRpeak, based on the comparative analysis of the groups, two studies reported a favorable effect [95%CI: 0.74 (0.31 - 1.16) p = 0.0007, N = 46] in the HIIT group (Figure 3). The studies that were not statistically analyzed (forest plot) showed, in the HIIT group, a positive effect on BP at rest and BPpeak (systolic and diastolic), brachial flow velocity, maximal muscle strength (1 RM), lean mass maintenance, and inflammatory markers. Some of those results are shown in Table 3. In addition, none of the studies reported a cardiovascular event and/or mortality associated with training, showing it to be a safe practice to be included in cardiac rehabilitation programs. Discussion The present systematic review with meta-analysis is the first to analyze the effect of HIIT on some health-related parameters of HTx recipients. The three studies included showed that HIIT improved VO 2 peak by 15%. Such increase is greater than that found in two systematic reviews withmeta-analysis that assessed the effect of different types of exercise 26 and of MICT 27 on the VO 2 peak of those patients. Although HIIT improves VO 2 peak, sometimes it is not indicated for HTx recipients because they have chronotropic insufficiency developed from cardiac denervation. 28 That incompetence hinders HR at rest (increase) and during close-to-peak exercise (decrease - HRpeak), decreasing the chronotropic reserve values. Thus, according to the studies assessed in this review, 8 to 12 weeks of HIIT intervention can decrease HR at rest and increase HRpeak. High‑intensity exercise (> 80%VO 2 peak or > 85%HRmax) might have improved the cardiocirculatory function, stimulating the sinus node faster, facilitating faster and better responses on HR at rest and HRpeak. 29 Although the literature shows an insufficient number of studies on HIIT and HTx recipients, that type of training can provide significant central and peripheral benefits to improve the clinical findings after surgery. 30 In addition, recent studies comparing the contribution of HIIT and MICT to the deficient variables of HTx recipients have shown the superior effect of HIIT. 31,32 Such results can indicate a possible change in paradigm regarding the recommendation of exercise prescription for HTx recipients. Thus, further studies are required to identify which training protocol better improves the deficient variables of those patients. Conclusion Our results showed that 8 to 12weeks of cardiac rehabilitation with HIIT were sufficient to significantly increase HRpeak and aerobic power of HTx recipients (men and women). Author contributions Conception and design of the research and Analysis and interpretation of the data: Perrier-Melo RJ, Costa MC; Acquisition of data, Statistical analysis and Obtaining financing: Perrier-Melo RJ; Writing of the manuscript and Critical revision of the manuscript for intellectual content: Perrier-Melo RJ, Figueira FAMS, Guimarães GV, Costa MC. Potential Conflict of Interest No potential conflict of interest relevant to this article was reported. Sources of Funding There were no external funding sources for this study. Study Association This article is part of the thesis of Doctoral submitted by Raphael José Perrier-Melo, from Universidade de Pernambuco. Ethics approval and consent to participate This article does not contain any studies with human participants or animals performed by any of the authors. 190