Comparing volume-clamp method and intra-arterial blood pressure measurements in patients with atrial fibrillation admitted to the intensive or medium care unit.

International guidelines highlight the importance of blood pressure (BP) in patients with atrial fibrillation (AF). However, BP measurement in AF is complicated by beat-to-beat fluctuation. Automated BP measurement devices are not validated for patients with AF and no consensus exists on how to measure BP in AF manually. Beat-to-beat BP measurement using the volume-clamp method (VCM) could represent a non-invasive method to accurately assess BP, but has not been validated in AF. 31 admitted patients with sustained AF and 10 control patients with sinus rhythm underwent simultaneous intra-arterial and non-invasive BP measurement using a VCM monitor (Nexfin, BMEYE, Amsterdam, The Netherlands). Patients with compromised peripheral perfusion, high doses of vasopressor drugs or peripheral edema were excluded. Differences in systolic, diastolic and mean BP of 5 (standard deviation; SD 8) mmHg (accuracy and precision) between both methods were considered acceptable. Additionally, the magnitude of beat-to-beat fluctuations in systolic BP of both methods was compared. In AF, the differences between noninvasive and invasive BP were -4 (SD 12), +1 (SD 7) and 0 (SD 8) mmHg for systolic, diastolic and mean BP respectively. Absolute differences in beat-to-beat BP fluctuations were 1.5 (IQR 0.8-3.8) mmHg. Accuracy of VCM in AF was similar to sinus rhythm. In conclusion, in patients with AF, accurate and precise measurement of non-invasive beat-to-beat BP measurement using the VCM is possible, the one exception being the precision of systolic BP. Beat-to-beat variability can be accurately reproduced.