RESUMO
BACKGROUND: The aim of this study was to determine the concordance between two instruments for measuring blood pressure (BP) and its modification due to the presence or absence of atrial fibrillation (AF). METHODS: In 107 patients with AF and a sinus rhythm (SR) of 100, BP was recorded using two sphygmomanometers: one automatic and the other manual. Four readings were made with each at 5-min intervals, and the mean was calculated for the statistical calculations. The correlation was determined using Pearson's correlation coefficient, and the concordance using the Bland-Altman plot and the κ index. RESULTS: The correlation coefficients (r) for the systolic (SBP) and diastolic BP (DBP) were 0.92 and 0.76. If the patient had AF, these were 0.91 and 0.75, respectively. The difference between the automatic and manual SBP measurements depending on whether the patient presented AF was -0.21 and -1.03 mm Hg. In DBP, this was -4.61 and 0.44 mm Hg. This discordance is not modified for low or high BP values, both in patients with AF and those without it. If we classify the patients as hypertensive or not (≥140/90 mm Hg), the concordance between both methods has high κ indices (0.72 and 0.89) both in AF and SR. CONCLUSION: There is a high correlation between both measurements, which decreased slightly in patients with AF. The difference when comparing the means is clinically irrelevant, and there is a substantial level of concordance between the two measurements for classifying patients as hypertensive or not.
