ABC | Volume 111, Nº3, September 2018

Original Article Kanar et al RV function after pulmonary rehabilitation program Arq Bras Cardiol. 2018; 111(3):375-381 Figure 2 – Correlation between right ventricular free wall longitudinal strain and six-minute walk test (6MWT) distance before pulmonary rehabilitation. (r = 0.58, p < 0.001). RV: right ventricular. 25.0 22.5 20.0 17.5 15.0 12.5 200 250 300 400 350 450 RV free wall longitudinal strain 6MWT distance before pulmonary rehabilitation contractility that are insufficient to affect global systolic function but have potential diagnostic and prognostic implications. Themain result of the study by Focardi et al. 18 was that free wall and global RV LS had a stronger correlation with the RV ejection fraction (RVEF) calculated by CMR (cardiac magnetic resonance) than conventional echocardiographic indices. Between the two, the highest diagnostic accuracy and the strongest correlation with the RVEF measured by CMR were observed for RV free wall longitudinal strain. 18 In our study, RV free wall LS had higher improvement than RV global LS after PR program. Moreover, it had a statistically significant correlation with exercise tolerance indices of the patients, such as 6MWT distance and BODE index. One possible explanation for this is that the thin RV free wall contracts against low pulmonary resistance, thus leading to significantly higher strain improvement after the decline of pulmonary resistance by means of PR program. On the other hand, the septum consists of the same fibers as those forming the LV and must handle loading conditions in the RV, as well as higher LV afterload.16 Nevertheless, this hypothesis must be confirmed by further studies. In addition, we chose to analyze the septum as part of the RV. It cannot be considered simply a part of the LV because its shortening contributes to the ejection phase of the RV, and any impairment in its contractility reduces RV performance. 14,19 Because of the paucity of data, no reference limits were established in the latest guidelines for RV global LS. Recent studies involving STE have focused on exploring RV function in patients with cardiopulmonary disease. Hardegree et al. 20 showed that RV free wall LS and 6MWT distance were increased after the initiation of medical therapy in patients with pulmonary arterial hypertension (PAH). Motoji et al. 21 showed that RV global LS < 19.4% indicates high risk of adverse cardiovascular events in patients with PAH. In addition, Guendouz et al. 22 reported that an absolute RV global LS value below 21% in patients with congestive heart failure identifies patients with high risk of adverse cardiac events. However, to the best of our knowledge, there are no published studies using STE to determine RV dysfunction and its improvement after PR program in patients with COPD. The effect of PR on RV function in patients with COPD has been explored in 2DE-based studies. Caminiti et al. 8 showed that TAPSE ≤ 16 mm was an indicator of decreased 6MWT distance at baseline and 6MWT distance change in COPD patients undergoing PR. According to our study, STE was more sensitive in determining RV dysfunction than 2DE. Tanaka et al., 23 in another 2DE-based study, showed an increase of MPI, and that there was a strong correlation between MPI and the MRC breathlessness 379