The purpose of this study was to verify the accuracy of the agreement between heart rate at the first ventilatory threshold (HRVT1) and heart rate at the end of the 6-min walk test (HR6MWT) in coronary artery disease (CAD) patients on β-blockers treatment. This was a cross-sectional study with stable CAD patients, which performed a cardiopulmonary exercise test (CPET) on a treadmill and a 6-min walk test (6MWT) on nonconsecutive days. The accuracy of agreement between HRVT1 and HR6MWT was evaluated by Bland-Altman analysis and Lin's concordance correlation coefficient (rc), mean absolute percentage error (MAPE), and standard error of estimate (SEE). Seventeen stable CAD patients on β-blockers treatment (male, 64.7%; age, 61±10 years) were included in data analysis. The Bland-Altman analysis revealed a negative bias of -0.41±6.4 bpm (95% limits of agreements, -13 to 12.2 bpm) between HRVT1 and HR6MWT. There was acceptable agreement between HRVT1 and HR6MWT (rc=0.84; 95% confidence interval, 0.63 to 0.93; study power analysis=0.79). The MAPE of the HR6MWT was 5.1% and SEE was 6.6 bpm. The ratio HRVT1/HRpeak and HR6MWT/HRpeak from CPET were not significantly different (81%±5% vs. 81%±6%, P=0.85); respectively. There was a high correlation between HRVT1 and HR6MWT (r=0.85, P<0.0001). Finally, the results of the present study demonstrate that there was an acceptable agreement between HRVT1 and HR6MWT in CAD patients on β-blockers treatment and suggest that HR6MWT may be useful to prescribe and control aerobic exercise intensity in cardiac rehabilitation programs.
Keywords: 6-Minute walk test; Cardiac rehabilitation; Coronary artery disease; Heart rate; Ventilatory threshold.
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