Bradycardia may determine blood-pressure variability: results from real life office measurements of over half a million members of a large health maintenance organization in Israel

Objective: Historically, guidelines for blood pressure (BP) 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. This translates to that, on average, the number of Korotkoff sounds (or oscillometric pulse waves) on which BP measurement is based is larger in patients with higher compared with lower pulse rate. It follows that the precision (and accuracy) of BP may be compromised in patients with lower heart rate, leading to higher intra-individual BP variability. In this study, we assess the association between heart rate and BP variability.

Design and Methods: Retrospective analysis of BP measurements of patients in a large health maintenance organization database. All BP measurements in adult patients with corresponding heart rate documentation were reviewed. For each heart rate category (6 categories between 40 and 99 beats per minute), all 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 pulse category.

Results: There were 551,595 unique patients with at least 3 BP measurements within a heart rate category (a total of 4,760,000 measurements) and 860,522 groups of 3 measurements or more per patient within a heart rate category. BP normalized coefficient of variance was inversely related to heart rate, ranging 0.0043 to 0.0003 (systolic), and 0.0024 to 0.0002 (diastolic), for the lowest to highest heart rate category, respectively. These results were consistent when sensitivity analyses were done with age below and above 60 years, gender, diabetes, kidney disease, treatment with β-blockers, calcium channel blockers, or no treatment.

Conclusions: BP variability is inversely associated with heart rate, especially in lower heart rate, likely reflecting less precise BP measurements where the “sample size” of heart beats 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.

留言 (0)

沒有登入
gif