Exercise tests in Chagas cardiomyopathy: an overview of functional evaluation, prognostic significance, and current challenges

Costa, Henrique Silveira; Lima, Márcia Maria Oliveira; Figueiredo, Pedro Henrique Scheidt; Lima, Vanessa Pereira; Ávila, Matheus Ribeiro; Menezes, Kenia Kiefer Parreiras de; Mendonça, Vanessa Amaral; Lacerda, Ana Cristina Rodrigues; Nunes, Maria Carmo Pereira; Mediano, Mauro Felippe Felix; Rocha, Manoel Otávio da Costa

doi:10.1590/0037-8682-0100-2020

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Revista da Sociedade Brasileira de Medicina Tropical

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Review Article • Rev. Soc. Bras. Med. Trop. 53 • 2020 • https://doi.org/10.1590/0037-8682-0100-2020 copy

Exercise tests in Chagas cardiomyopathy: an overview of functional evaluation, prognostic significance, and current challenges

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Abstract

Patients with Chagas cardiomyopathy (ChC) usually progress with fatigue and dyspnea. Exercise tests are valuable for the functional evaluation of these patients. However, information about the applicability of the exercise tests is scattered, and no studies have systematically reviewed the results. Thus, the present review explored the general aspects and prognostic value of exercise tests in patients with ChC. A literature search of the MEDLINE, Web of Science, CINAHL, Scopus, and LILACS databases was performed to identify relevant studies. There were no data restrictions, and articles that met the objective of the study were selected. Articles written in English, Portuguese, and Spanish were considered, and 25 articles were finally included. The peak oxygen uptake (VO2peak) was correlated with demographic and echocardiographic variables. Echocardiographic features of the left ventricular diastolic function and right ventricular systolic function appeared to be determinants of functional capacity, in addition to age and sex. VO2peak was associated with higher mortality, especially in patients with dilated ChC. The minute ventilation/carbon dioxide production slope (VE/VCO2 slope) was a strong predictor of survival; however, more studies are needed to verify this observation. Field tests showed moderate to strong correlation with VO2peak and thus may be inexpensive tools for the functional evaluation of patients with ChC. However, few studies have verified their prognostic significance. While exercise tests are useful tools for functional assessment, information is scarce regarding further considerations, and many of the criteria are based on guidelines for other heart diseases.

Keywords:
Chagas disease; Chagas cardiomyopathy; Exercise test; Exercise tolerance; Evaluation; Prognosis

STUDY	POPULATION	EXERCISE TEST	RESULTS
Mady et al. (1986)²²22. Mady C, Junior PY, Barreto ACP, Saraiva JF, Vianna CdB, Azul LGdS, et al. Estudo da capacidade funcional máxima pela ergoespirometria em pacientes portadores da doença de Chagas. Arq Bras Cardiol. 1986;47(3):201-5.	13 patients with ChC and preserved LVEF (30±5.76 years) and 15 patients with dilated ChC (30±6.82 years, NYHA II-III)	CPET (Naughton protocol, treadmill)	The VO2peak, O2 pulse, HR, VE, and VCO2 in patients with dilated ChC were significantly lower compared to those in patients with ChC and preserved LVEF (p<0.05).
Pedrosa; Campos (2004)³³33. Pedrosa RC, Campos MCd. Teste ergométrico e o Holter de 24 horas na detecção de arritmias ventriculares complexas em diferentes estádios da cardiopatia chagásica crônica. Rev Soc Bras Med Trop . 2004;37(5):376-83.	20 patients with ChC and preserved LVEF (30% male, 51.2±11 years, LVEF: 59.3±14%) and 20 patients with dilated ChC (20% male, 55.8±10 years, LVEF: 37.6±9.3%)	CPET (Bruce protocol, treadmill)	No differences (p>0.05) were observed in the prevalence of ventricular extrasystoles, pairs of extrasystoles, nonsustained ventricular tachycardia, and sustained monomorphic ventricular tachycardia, detected by 24-h Holter monitoring and those induced by exercise both in dilated ChC and with preserved LVEF.
Rocha et al. (2005)²¹21. Rocha ALL, Rocha MOdC, Teixeira BOS, Lombardi F, Abreu CDG, Bittencourt RJ, et al. Índice cronotrópico-metabólico na doença de Chagas. Rev Soc Bras Med Trop . 2005;38(5):373-6.	154 patients with ChC and preserved LVEF [57% male, 41.7±9.3 years, LVEF: 62 (58-65)%] and 17 patients with dilated ChC [59% male, 42.8±9.2 years, LVEF: 35 (31-39)%]	Maximal Exercise Testing (Bruce protocol, treadmill)	No differences were observed between groups with preserved LVEF and dilated ChC in VO2peak, maximum HR, delta HR, and effort time (p>0.05).
Lima et al. (2010)²⁵25. Lima MM, Nunes MC, Rocha MO, Beloti FR, Alencar MC, Ribeiro AL. Left ventricular diastolic function and exercise capacity in patients with Chagas cardiomyopathy. Echocardiography. 2010;27(5):519-24.	40 patients with dilated ChC; 49±8 years; 58% male; NYHA I-II; LVEF: 36.3±7.8%	Maximal Exercise Testing (Bruce protocol, treadmill)	The VO2peak was correlated with E/E’ ratio (r= -0.516; p=0.001) but not with LVEF, LVDd, and BNP. The predictors of VO2peak in the final multivariate model were age, female sex, E/E’ ratio, and left atrial volume (LAV) (r²=0.521).
Nunes et al. (2010)²⁷27. Nunes Mdo C, Beloti FR, Lima MM, Barbosa MM, Pinto Filho MM, de Barros MV, et al. Functional capacity and right ventricular function in patients with Chagas heart disease. Eur J Echocardiogr. 2010;11(7):590-5.	65 patients with ChC (comprising dilated ChC and with preserved LVEF); 48.6±9.1 years; 60% male; NYHA I-II); LVEF: 43.1±11.4%	Maximal Exercise Test (treadmill, Bruce protocol)	The VO2peak was correlated with LVDd/BSA (r= -0.38; p=0.002), e’ (r= 0.40; p=0.001), E/e’ ratio (r= -0.37; p=0.003), RV e’ (r= 0.29; p=0.025), RV e’/A’ ratio (r= 0.41; p=0.001), RV systolic velocity (r= 0.45; p<0.001), RV Tei index (r= -0.28; p=0.029), and PASP (r= -0.36; p=0.009). The VO2peak did not correlate with LVEF, E/A ratio, DT, LA volume index, E/Vp. The independent predictors of VO2peak were age, female sex and RV systolic velocity (r²=0.71).
Alvarenga et al. (2014)²⁴24. Alvarenga JCd, Jansen PD, Marques VEG, Costa HS, Sousa GRd, Souza ACd, et al. Relação entre a fração de ejeção do ventrículo esquerdo e razão e/e' com a capacidade funcional na cardiopatia chagásica. Rev Assoc Med Minas Gerais. 2014;24(Supl 9):S20-S5.	35 patients with ChC (dilated and with preserved LVEF); 47.11±8.15 years, 65% male; NYHA I-III; LVEF: 59.0 [41.0-64.0]	CPET (ramp protocol, treadmill)	In the overall study population, a significant correlation was observed between VO2peak and LVEF (r=0.536, p=0.001) and E/e' ratio (r=-0.399; p=0.022). In patients with dilated ChC (n=16), the VO2peak was also correlated with LVEF (r=0.611, p=0.016) and with the ratio E/e' (r=-0.601, p=0.018). In the multivariate analysis, LVEF and E/e’ ratio were strong predictors of VO2peak (r² = 0.723) only in patients with dilated ChC.
Costa et al. (2014)²³23. Costa HS, Lima MM, de Sousa GR, de Souza AC, Alencar MC, Nunes MC, et al. Functional capacity and risk stratification by the Six-minute Walk Test in Chagas heart disease: comparison with Cardiopulmonary Exercise Testing. Int J Cardiol . 2014;177(2):661-3.	41 patients with ChC (dilated and with preserved LVEF); 47.8±8.3 years; 68% male; NYHA I-III	CPET (ramp protocol, treadmill)	Patients with dilated ChC had lower VO2peak (p=0.001) and 6MWT distance (p=0.045) values and higher VE/VCO2 slope (p=0.029) value compared to those in patients with ChC and preserved LVEF.
Costa et al. (2017)²⁶26. Costa HS, Lima MM, Alencar MC, Sousa GR, Figueiredo PH, Nunes MC, et al. Prediction of peak oxygen uptake in patients with Chagas heart disease: Value of the Six-minute Walk Test. Int J Cardiol . 2017;228:385-7.	81 patients with ChC (dilated and with preserved LVEF); 48.6±8.1 years; 63% male; NYHA I-III); LVEF: 43.7±13.7%	Maximal Exercise Test (treadmill)	The VO2peak was correlated with age (r= -0.490; p<0.001), sex (r = 0.283; p=0.010), body mass index (r= -0.333; p=0.002), NYHA functional class (r= -0.667; p<0.001), and 6MWT distance (r=0.527; p<0.001). The VO2peak was predicted by sex, NYHA functional class, 6MWT distance, age, and body mass index
Costa et al. (2017)²⁸28. Costa HS, Lima MMO, Nunes MCP, Sousa GR, Almeida FRd, Figueiredo PHS, et al. Inspiratory muscle weakness in patients with Chagas heart disease: Echocardiographic and functional predictors. IJC Metab Endocr. 2017;14:21-5.	48 patients with ChC (dilated and with preserved LVEF); 56.4 (53.3-59.5) years; 29% male; NYHA I-III; LVEF: 54.3 (48.6-59.9)%	CPET (ramp protocol, treadmill)	VE/VCO2 slope was correlated with the percentage of maximal inspiratory pressure (r= -0.446; p=0.004). The VO2peak was not correlated with maximal inspiratory pressure. In the final multivariate model, patients with impaired VE/VCO2 slope had a 1.2-fold increased risk for inspiratory muscle weakness (prevalence ratio 1.2, 95% CI 1.1 to 1.5, p = 0.001).

STUDY	POPULATION	EXERCISE TEST	RESULTS
De Paola et al. (1995)⁴³43. de Paola AA, Gomes JA, Terzian AB, Miyamoto MH, Martinez Fo EE. Ventricular tachycardia during exercise testing as a predictor of sudden death in patients with chronic chagasic cardiomyopathy and ventricular arrhythmias. Br Heart J. 1995;74(3):293-5.	69 patients with ChC (dilated and preserved LVEF), 46±12 years; 54% male; NYHA I-III, LVEF 46.6±18.6%. Follow-up period: 24±15 months. Endpoint: sudden death	Maximal Exercise Test (Bruce protocol, treadmill)	The number of patients with ventricular tachycardia at baseline was significantly higher in the sudden cardiac death group when compared to survivors (p<0.05).
Silva et al. (2017)⁴¹41. Silva RRD, Reis MS, Pereira BB, Nascimento EMD, Pedrosa RC. Additional value of anaerobic threshold in a general mortality prediction model in a urban patient cohort with Chagas cardiomyopathy. Rev Port Cardiol. 2017;36(12):927-34.	45 patients with dilated ChC, 50.24±10.79 years; 100% male. Endpoint: death	CPET (cycle ergometer)	The VO2peak AT is an independent predictor of death (AUC=0.706). When both Rassi score and AT were defined as independent variables. VO2peak AT increases the accuracy of the Rassi score for mortality prediction by 5%.
Souza et al. (2015)⁴²42. Souza FCdCe, Lorenzo AD, Serra SM, Colafranceschi AS. Avaliação do Prognóstico na Cardiomiopatia Chagásica através do Teste Cardiopulmonar de Exercício. Int J Cardiovasc Sci. 2015;28(6):440-50.	21 patients with dilated ChC, 54.5±11.9 years, 38.1% male, NYHA III-IV, LVEF 29.2± 6.0%. Follow-up period: 24 months. Endpoint: cardiac death	CPET (ramp protocol, treadmill)	Differences between non-survivors ChC compared to survivors included lower peak HR (p=0.026), peak SBP (p=0.038), VO2peak (p=0.043), VO2peak AT (p=0.016), circulatory power (p=0.006) and ventilatory power (p=0.008). In the logistic regression, only circulatory power was independently associated with survival (OR 17.3 [95% CI: 1.39 to 217.0]). The circulatory power showed good accuracy in identify mortality (cut-off point ≤ 1280).
Ritt et al. (2013)¹³13. Ritt LE, Carvalho AC, Feitosa GS, Pinho-Filho JA, Andrade MVS, Feitosa-Filho GS, et al. Cardiopulmonary exercise and 6-min walk tests as predictors of quality of life and long-term mortality among patients with heart failure due to Chagas disease. Int J Cardiol . 2013;168(4):4584-5.	55 patients with dilated ChC, 52±9 years, 69% male, NYHA II-IV, LVEF 27.6±6.6%. Follow-up period: 32±19 months. Endpoint: cardiac death	CPET (ramp protocol, treadmill)	The VO2peak (p=0.03) and VE/VCO2 slope (p=0.01) differed significantly between survivors and non-survivors. The VO2peak was correlated with MLwHRQ (r= -0.301; p=0.02) and showed good accuracy in identifying mortality (cut-off ≤18 mL/kg/min). The VE/VCO2 slope showed good accuracy in identifying mortality (cut-off >32.5. After adjusting for age, LVEF, and Chagas score, VE/VCO2 slope remained an independent predictor of mortality (adjusted HR: 2.80, 95% CI: 1.30 to 5.80, and p=0.001 for those with VE/VCO2 slope ≥32.5).
Pedrosa et al. (2011)⁴⁴44. Pedrosa RC, Salles JH, Magnanini MM, Bezerra DC, Bloch KV. Prognostic value of exercise-induced ventricular arrhythmia in Chagas' heart disease. Pacing Clin Electrophysiol . 2011;34(11):1492-7.	130 patients with ChC (dilated and with preserved LVEF), 50.7±10.3 years, 40.8% male. Follow-up period: 9.9 years (range, 132 days to 17 years). Endpoint: cardiovascular death	CPET (Bruce protocol)	The prevalence of EIVA was 43.1%. Sex, age, and cardiothoracic index were not associated with EIVA. LVEF showed a statistically significant association with EIVA (p=0.01). The presence of EIVA alone was not a predictor of mortality but predicted mortality in Cox analysis, only when associated with age and cardiothoracic index >0.5 (hazard ratio=4.3 [95% CI: 1.6 to 11.4]; p=0.004).
Costa et al. (2018)⁴⁰40. Costa HS, Lima MMO, Figueiredo PHS, Martinelli PM, Camargos ER, Chaves AT, et al. Prognostic value of serum brain-derived neurotrophic factor levels in patients with Chagas cardiomyopathy. Mem Inst Oswaldo Cruz. 2018;113(10):e180224.	49 patients with dilated ChC, 50±7 years; 57% male; NYHA I-III, LVEF: 36.0 [31.0-41.0]%. Follow-up period: 39±14 months. Endpoint: cardiac death	Maximal Exercise Testing (Bruce protocol, treadmill)	Survivors had higher VO2peak (p=0.048) than non-survivors. In the final model, VO2peak (hazard ratio 1.2, 95% CI: 1.0 to 1.3; p=0.009) remained an independent predictor of cardiac death in ChC. The optimal cut-off point for VO2peak in predicting death was 25 mL/kg/min. However, the established cutoff point failed to demonstrate a difference between the groups with VO2peak below and above 25 mL/kg/min.
Mady et al. (1994)¹²12. Mady C, Cardoso R, Barretto A, da Luz PL, Bellotti G, Pileggi F. Survival and predictors of survival in patients with congestive heart failure due to Chagas' cardiomyopathy. Circulation. 1994;90(6):3098-102.	104 patients with dilated ChC, 40.3±9.0 years; 100% male; NYHA II-IV, LVEF: 37.4±11.1%. Follow-up period: 41±12 months. Endpoint: cardiac death	CPET (Naughton protocol, treadmill)	The survivor group showed higher LVEF (=0.001), higher VO2peak (p=0.001), and better NYHA functional class (p=0.001) than that of those in the non-survivor group. In the multivariate model, VO2peak (p=0.001) and LVEF (p=0.008) remained independent predictors of cardiac death. Survival was significantly better in patients with VO2peak >20 mL/kg/min.
Costa et al. (2019)³⁹39. Costa HS, Lima MMO, Figueiredo PHS, Chaves AT, Nunes MCP, da Costa Rocha MO. The prognostic value of health-related quality of life in patients with Chagas heart disease. Qual Life Res. 2019;28(1):67-72.	75 patients with ChC (dilated and with preserved LVEF), 48.4±8.0 years; 61% male; NYHA I-III, LVEF: 41.0 [35.0-53.5]%. Follow-up period: 41±12 months. Endpoint: death, heart transplantation, or ischemic event	Maximal Exercise Test (Bruce protocol, treadmill)	Patients with adverse events had lower LVEF (p=0.002), higher LVDD (p=0.019) and worse mental component of HRQoL (p=0.043) compared to those in patients without adverse events. No differences were observed in age, sex, NYHA functional class, VO2peak, %HR achieved during exercise test, and HR recovery after exercise testing between groups. In the univariate analysis, VO2peak, %HR achieved during exercise test, and HR recovery after exercise testing were not associated with adverse events.

STUDY	POPULATION	EXERCISE TESTS	RESULTS
Sousa et al. (2008)⁵⁰50. Sousa L, Botoni FA, Britto RR, Rocha MO, Teixeira AL Jr., Teixeira MM, et al. Six-minute walk test in Chagas cardiomyopathy. Int J Cardiol . 2008;125(1):139-41.	38 patients with dilated ChC, 48±10 years; 68% male; NYHA I-III, LVEF<55%	6MWT	The 6MWT distance was correlated with MCP-1 values (r=−0.358, p=0.04), BNP levels (r=−0.349, p=0.04), and LVEF (r=0.451, p=0.004) but not with NYHA functional class (r=−0.130, p=0.435).
Dourado et al. (2010)⁵¹51. Dourado KCC, Bestetti RB, Cardinalli-Neto A, Cordeiro JA. Evaluation of the six-minute walk test in patients with chronic heart failure associated with Chagas' disease and systemic arterial hypertension. Rev Soc Bras Med Trop . 2010;43(4):405-8.	60 patients with ChC: 55±14 years; 68% male; 25% in NYHA III-IV; LVEF: 44.0±13.8% and 38 patients with ChC and systemic arterial hypertension: 63±10 years; 88% male; 21% in NYHA III-IV; LVEF: 51.8±12.9%	6MWT	No difference in 6MWT distance between groups with and without systemic arterial hypertension (p>0.05). In the systemic arterial hypertension group, the 6MWT distance was correlated with MLwHFQ (r=-0.51; p=0.001). In the group without systemic arterial hypertension, the 6MWT distance was correlated with hemoglobin levels (r=0.34; p=0.007) and MLwHFQ (r= -0.38; p=0.003).
Ritt et al. (2013)¹³13. Ritt LE, Carvalho AC, Feitosa GS, Pinho-Filho JA, Andrade MVS, Feitosa-Filho GS, et al. Cardiopulmonary exercise and 6-min walk tests as predictors of quality of life and long-term mortality among patients with heart failure due to Chagas disease. Int J Cardiol . 2013;168(4):4584-5.	55 patients with dilated ChC (52±9 years, 69% male, NYHA II-IV, LVEF: 27.6±6.6%). Follow-up period: 32±19 months; endpoint: cardiac death	CPET (ramp protocol, treadmill) and 6MWT	The 6MWT was correlated with MLwHRQ (r=-0.375; p=0.007) and was the only independent determinant of MLwHRQ (each 10-min increase in distance walked was associated with a 0.7-point reduction in MLHFQ score); no prognostic value.
Costa et al. (2014)⁵⁶56. Costa HS, Alves RL, da Silva SA, Alencar MC, Nunes Mdo C, Lima MM, et al. Assessment of Functional Capacity in Chagas Heart Disease by Incremental Shuttle Walk Test and its Relation to Quality-of-Life. Int J Prev Med. 2014;5(2):152-8.	35 patients (dilated and preserved LVEF), 47.1±8.2 years, 66% male, NYHA I-III and LVEF: 59 (41-64)%	CPET (ramp protocol, treadmill) and ISWT	ISWT distance was correlated with VO2peak (r=0.587; p<0.001), MLwHRQ score (r=-0.460; p=0.006), and SF-36 domains physical functioning (r=0.435; p=0.009), role physical (r=0.447; p=0.008), and mental health (r=0.430; p=0.011).
Costa et al. (2014)²³23. Costa HS, Lima MM, de Sousa GR, de Souza AC, Alencar MC, Nunes MC, et al. Functional capacity and risk stratification by the Six-minute Walk Test in Chagas heart disease: comparison with Cardiopulmonary Exercise Testing. Int J Cardiol . 2014;177(2):661-3.	41 patients with ChC (dilated and with preserved LVEF), 47.8±8.3 years; 68% male; NYHA I-III	CPET (ramp protocol, treadmill) and 6MWT	Patients with dilated ChC showed lower 6MWT distance (p=0.045) compared to that in patients with preserved LVEF. The 6MWT distance was correlated with VO2peak (r=0.586; p<0.001) but not with VE/VCO2 slope (r=−0.046; p=0.776). The 6MWT distance was correlated with VO2peak in both dilated ChC (n=20, r=0.612; p=0.005) and preserved LVEF (n= 21, r=0.463; p=0.035) groups.
Alves et al. (2016)⁵⁵55. Alves R, Lima MM, Fonseca C, Dos Reis R, Figueiredo PH, Costa H, et al. Peak oxygen uptake during the incremental shuttle walk test in a predominantly female population with Chagas heart disease. Eur J Phys Rehabil Med. 2016;52(1):20-7.	32 patients with ChC (6 with dilated ChC and 26 with preserved LVEF), 58.8±9.0 years; 18.7% male; NYHA I-III, LVEF: 62.4±13.4%	CPET (Bruce protocol, treadmill) and ISWT	The ISWT distance was correlated with VO2peak (r=0.456; p=0.009). In women, the VO2peak was predicted by the formula 13.97 + 0.02 x ISWT distance (for NYHA I) or 11.36 + 0.02 x ISWT distance (for NYHA³II). In men, the VO2peak was predicted by the formula 12.21 + 0.03 x ISWT distance (for NYHA I) or 9.60 + 0.03 x ISWT distance (for NYHA³II).
Chambela et al. (2017)⁵³53. Chambela MC, Mediano MFF, Ferreira RR, Japiassu AM, Waghabi MC, da Silva GMS, et al. Correlation of 6-min walk test with left ventricular function and quality of life in heart failure due to Chagas disease. Trop Med Int Health. 2017;22(10):1314-21.	40 patients with dilated ChC, 60±12 years; 47% male; NYHA I-III, LVEF: 35±12%	6MWT	The 6MWT distance was correlated with BNP (r=-0.37; p=0.02) and echocardiographic features, including E velocity (r=-0.38; p=0.002), E/E’ ratio (r=-0.32; p=0.05), LV diastolic dysfunction (r=-0.36; p=0.03), mitral regurgitation (r= -0.53; p<0.001), and PASP (r=-0.42; p=0.02). The 6MWT distance was also correlated with the SF-36 domains physical functioning (r=0.46; p=0.008), physical role functioning (r=0.37; p=0.04), and bodily pain (r=0.43; p=0.014) as well as MLwHRQ (r=-0.54; p=0.002).
Costa et al. (2017)²⁶26. Costa HS, Lima MM, Alencar MC, Sousa GR, Figueiredo PH, Nunes MC, et al. Prediction of peak oxygen uptake in patients with Chagas heart disease: Value of the Six-minute Walk Test. Int J Cardiol . 2017;228:385-7.	81 patients with ChC (dilated and with preserved LVEF), 48.6±8.1 years; 63% male; NYHA I-III, LVEF: 43.7±13.7%	Maximal Exercise Test (treadmill) and 6MWT	The VO2peak was correlated with the 6MWT distance (r=0.527; p<0.001) and VO2peak was predicted by the formula 53.43 + (1.35 × sex) - (5.59 × NYHA) + (0.01 × 6MWT distance) - (0.29 × age) - (0.035 × BMI).
Costa et al. (2017)⁵⁴54. Costa SdA, Rassi S, Freitas EMdM, Gutierrez NdS, Boaventura FM, Sampaio LPdC, et al. Prognostic Factors in Severe Chagasic Heart Failure. Arq Bras Cardiol . 2017;108(3):246-54.	60 patients with dilated ChC, 52.6±9.4 years; LVEF: 27.1±5.5%. Follow-up period: 7.5 years. Endpoint: death	6MWT	The 6MWT was not a predictor of death. The independent predictors of death were non-sustained ventricular arrhythmias in 24h Holter monitoring and left atrium volume index (p<0.05 for both).
Costa et al. (2018)⁴⁹49. Costa HS, Lima MMO, Lage SM, da Costa FSM, Figueiredo PHS, da Costa Rocha MO. Six-minute walk test and incremental shuttle walk test in the evaluation of functional capacity in Chagas heart disease. J Exerc Rehabil. 2018;14(5):844-50.	35 patients with ChC (dilated and with preserved LVEF), 47.1±8.2 years; 66% male; NYHA I-III, LVEF: 59.0 [41.0-64.0]	CPET (ramp protocol, treadmill), 6MWT and ISWT	The VO2peak was correlated with 6MWT distance (r=0.577; p<0.001) and ISWT distance (r=0.587; p<0.001). Only the ISWT was correlated with the VE/VCO2 slope (r=-0.339; p=0.003). The optimal distances to identify patients with functional impairment were 520 m for the 6MWT and 400 m for the ISWT.

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[1] Corresponding author: Dr. Henrique Silveira Costa. e-mail:henriquesilveira@yahoo.com.br