Brachial Systolic Pressure Averages Twice Diastolic: Evidence From Invasive High-Fidelity Pressure Recordings

Systolic arterial pressure (SAP) and diastolic arterial pressure (DAP) are key measurements in cardiovascular assessment. A recent invasive study by our group found that SAP averages twice DAP at the radial and femoral levels. Whether this relationship applies to the brachial artery and central aorta remains unknown.

Guided by 2 systematic reviews, we conducted a secondary data analysis of studies that simultaneously reported high-fidelity invasive brachial and aortic pressures in adults undergoing cardiac catheterization. Allowing a  ± 2.5% measurement error in SAP and DAP, we defined an acceptable SAP/DAP ratio range of 1.90 to 2.10.

Seven studies were included (n = 268; 69% male; mean age of 62 years). The weighted mean brachial SAP/DAP ratio was 1.98 (141.6/71.6 mmHg) across the cohort and aligned with our hypothesis in 6 studies (n = 256; 95% of the population). The one study that did not support the hypothesis was a letter-format publication with a small sample size (n = 12). The hypothesis regarding the aortic SAP/DAP ratio was largely unsupported, being rejected in 6 studies (n = 232) and in the pooled data (1.89 = 134.7/71.4).

This preliminary analysis shows that brachial SAP averages twice DAP within a minimal margin of measurement error. These findings highlight a potentially important hemodynamic feature of the brachial artery-and, more generally, of peripheral large arteries, in contrast to the aorta. However, broader validation is needed to assess the clinical relevance of these results beyond the predominantly older male cohort referred for catheterization, and the physiological basis of this pattern also warrants further investigation.