Abstract P2053: Blood Pressure Variability is Higher When Pulse Rate is Lower, in a Large Outpatient Database

Abstract

Historically, guidelines for blood pressure measurement recommended adjusting the cuff deflation rate to the patient's heart rate (2-3 mmHg per heartbeat).Current guidelines recommend a fixed cuff deflation rate of 2 mmHg/sec.. In this study, we assess the association between pulse rate (PR) and BP variability. All BP measurements in adult patients with corresponding PR documentation were reviewed in a large outpatient database. In each category (6 categories between 40 and 99 bpm), patients with at least 3 BP readings within that category were included. In each category, systolic and diastolic BP coefficient of variance (corrected for sample size) was plotted against the PR category. There were 551,595 unique patients with a total of 4,760,000 measurements, and 860,522 groups of 3 measurements or more per patient within a PR category. BP normalized coefficient of variance was inversely related to PR (Figure), ranging 0.0043 to 0.0003 (Systolic), and 0.0024 to 0.0002 (Diastolic), for the lowest to highest heart rate category, respectively. BP variability is inversely associated with PR, especially in lower PR, likely reflecting less precise BP measurements where the "sample size" of pulse is small. The observed effect compromising precision might be accompanied by a concomitant reduced accuracy of BP measurement which is another theoretical implication of a smaller "sample size", leading to a systematic bias towards measuring lower and higher than real systolic and diastolic BP respectively.