Comparison of Noninvasive Blood Pressure Measurements in Patients With Atrial Fibrillation

Background and Research Objective: Limited research is available on the accuracy of automatic blood pressure (BP) measurement devices in patients with irregular rhythms. The purpose of this study was to examine the agreement between different methods for noninvasive BP measurement in patients with atrial fibrillation. Subjects and Methods: In a convenience sample of hospitalized patients with atrial fibrillation, a method-comparison study design was used to examine the agreement between 2 noninvasive devices for BP measurement (manual, automated). Blood pressure was obtained sequentially, with each device following manufacturer's directions and American Heart Association guidelines for BP determination and with BP order determined by random assignment. Heart rate and rhythm were determined from a continuous electrocardiographic monitoring. Heart rate was also recorded from the automated BP device. Differences and limits of agreement between the automated and reference standard (manual) BP devices were calculated and graphed according to the Bland-Altman method. Student t test was used to test differences in BP obtained with the 2 devices, as well as heart rate differences between the electrocardiographic monitor and automated BP device. The level of significance for all tests was set at 0.05. Results: 53 participants were observed. Bland-Altman analysis found a bias plus/minus precision of -0.91 +/- 11.4 mm Hg for systolic BP and 3.3 +/- 6.9 mm Hg for diastolic BP. A significant difference was found for the diastolic BP obtained with the automated device and with that of the manual device (t(52) = 3.51, P =.0009) and for heart rate differences between the automated BP device and the cardiac monitor (t(52) = 2.4, P =.0217). Conclusion: This study confirms that in the presence of irregular cardiac rhythms, diastolic BP and heart rate cannot reliably be measured with an automated BP device.