ABC | Volume 113, Nº2, August 2019

Original Article Maia et al Global Longitudinal Strain in Functional Capacity Arq Bras Cardiol. 2019; 113(2):188-194 Table 1 – Characteristics of the study population Variable (n = 26) Age (years), mean ± DP 47.31 ± 12.71 Gender: n (%) Men 15 (57.7) Women 11 (42.3) BMI (Kg/m²): Mean ± DP 29.31 ± 5.38 Comorbidities: n (%) SAH 20 (77) DM 15 (61) HF Etiology: n (%) Ischemic 6 (23) Hypertensive 10 (39) Myocarditis 4 (15) Chagas' Disease 1 (4) Idiopathic 5 (19) Medication: n (%) ACEI/ARB 23 (88) Beta blocker 26 (100) Diuretics K-sparing 22 (84) LVEF (%) (mean ± DP) 28,0 ± 8.62 Strain (%) (mean ± DP) -7.5 ± 3.92 maxVO 2 (mean ± DP) 19.09 ± 9.52 VE/VCO 2 slope (mean ± DP) 39.43 ± 9.91 HRR (bpm) (mean ± DP) 19.65 ± 17.42 T 1/2 VO 2 (s) (mean ± DP) 168.61 ± 43.90 BMI: body mass index; SAH: systemic arterial hypertension; DM: diabetes mellitus; ACEI/ARB: converting the angiotensin-converting enzyme inhibitor/angiotensin receptor blocker; LVEF: left ventricular ejection fraction; maxVO 2 : maximal oxygen consumption; VE/VCO 2 slope: slope of the VE/VCO 2 curve; HRR: heart rate recovery; T 1/2 VO 2 : time to VO 2 halving recovery. Correlation of CPET variables with LVEF and GLS measurements When comparing the CPET with LVEF data (Table 2), a positive correlation was observed only with maxVO 2 (r = 0.585, p = 0.02) and negative with T 1/2 VO 2 (r = –0.530; p = 0.005). For the other variables, LVEF showed no correlation, Table 2. The GLS showed significant correlation with all analysed CPET variables. This parameter was positively correlated with maxVO 2 and HRR and inversely with VE/VCO 2 slope and T 1/2 VO 2 , Table 2 and Figure 1. Regarding VO 2 group > 14 mL/kg/min and/or VE/VCO 2 slope < 35 and VO 2 group < 14 mL/kg/min and VE/VCO 2 slope > 35, there were no differences in clinical variables, comorbidities and medications used. However, echocardiographic variables showed differences, as shown in Table 3. The area under the ROC curve (Figure 2) for the GLS index value as a predictor of poor functional capacity and worse prognosis was 0.88 (95% CI = 0.75 to 1.00), with a sensitivity of 75%, specificity of 83%, positive predictive value of 67%, and negative predictive value of 88%, for a cut-off GLS value of -5.7%, p = 0.03. Discussion In this study, in patients with systolic HF referred for a cardiopulmonary rehabilitation program, the GLS was significantly associated with all functional CPET parameters. It seems to be more accurate than LVEF in classifying patients with HF according to the functional capacity and thus may stratify which patients have a poor prognosis and therefore to deserve more differentiated treatment, such as heart transplantation. Previous studies have demonstrated that LVEF has no correlation with functional capacity. 1,10 However, there is limited data on the association between exercise tolerance and the results of analysis by cardiac strain. This study showed that LVEF was associated with maxVO 2 and T 1/2 VO 2 , however, showed no correlation with the other CPET variables. Whereas peak VO 2 values and VE/VCO 2 slope are parameters which help in end-stage HF decision making 4,16 and that in this study, the GLS value was correlated with all these variables, we could suggest that the GLS may have a prognostic significance in this group of patients. In addition, GLS correlation with maxVO 2 and T 1/2 VO 2 was better than LVEF, thus demonstrating that the GLS is a more accurate tool. Hasselberg et al., 11 in their study that evaluated HF patients, either with normal or reduced LVEF, were able to show the importance of GLS as a predictor of exercise capacity in patients with preserved LVEF HF. 11 However, these authors have failed to demonstrate this relationship in patients with reduced LVEF. In the present study, we observed this correlation between GLS and functional capacity. This may have occurred since our study evaluated patients in more advanced stages of cardiac dysfunction. The average GLS in our study was worse than the Hasselbach study. 11 The T 1/2 VO 2 has also proven an important tool for predicting outcomes. The longer the VO 2 recovery time of HF patients after physical exercise, the worse the cardiovascular prognosis. 18-21 Our study demonstrated that the GLS was able to determine patients that have delayed recovery of VO 2 . The lower the value of GLS, the greater the time required for the post-physical effort VO 2 to be reduced to half, suggesting the hypothesis that the GLS could estimate the prognosis of the patient. Another evidence that supports the prognostic importance of GLS was dysautonomia analysis. It is known that there is a relationship between HRR in the first minute after physical exercise with mortality. The cardiovascular prognosis appears to be independent of symptoms, the type of recovery protocol, LVEF, and severity of coronary lesions in coronary angiography. 7-9,21,22 This study showed a direct relationship between the GLS value and HRR in the first minute after effort, with a less accentuated drop in heart rate in patients who had a lower GLS value. 190