ABC | Volume 110, Nº5, May 2018

Original Article Oliveira et al Exercise in acute heart failure Arq Bras Cardiol. 2018; 110(5):467-475 Figure 1 – Six minute walk test distance achieved at D1 and D10 in Control, ET+Sham and ET+NIV groups. Notes: Open circles: individual distance achieved at D1 and D10. Dark square: mean and standard deviation of distance at D1 and D10. * p < 0.05 vs. Control; † p < 0.05 vs. ET+Sham; ‡ p < 0.05 vs. D1. A B C 500 400 300 200 100 0 500 400 300 200 100 0 500 400 300 200 100 0 6 minute walk test (m) 6 minute walk test (m) 6 minute walk test (m) Control ET+Sham ET+NIV D1 D10 *†‡ *‡ Another important finding in our study was the increase in exercise tolerance in patients who underwent aerobic exercise. Actually, this finding has clinical implications. The 6MWT distance is associated with clinical outcome and quality of life in patients with HF. 29 Furthermore, it is possible that the aerobic exercise training improves exercise tolerance even in hospitalized HF patients. In order to investigate if the use of NIV could have additional effects on aerobic exercise training, we found that ET+NIV group had improved exercise performance and decreased dyspnea during the exercise. In fact, NIV might reduce venous return and cardiac preload, 30 which could explain our findings. Another finding of great interest and clinical relevance was that the ET+NIV had a shorter hospital stay, enhanced 6MWT distance and exercise time compared to ET+Sham group, suggesting that the NIV can enhance the effectiveness of aerobic exercise in acute HF patients. The rationale for this theory is that NIV combined to exercise has some influence on redistribution of muscle blood flow. 16 Dempsey et al. 31 suggested that respiratory muscles influence vascular diameter and peripheral vasoconstriction. Respiratory muscles might compete for the reduced blood flow during exercise with the peripheral muscles, thereby promoting an inadequate oxygen transport and exercise fatigue. In addition, fatiguing contractions could stimulate IV phrenic afferents by muscle metabolic production, increasing sympathetic vasoconstriction with consequent reduction in oxygen delivery. 31,32 471