| Summary: | Background: The Riva-Rocci brachial blood pressure (BP) method purported to measure aortic BP, and this remains the cornerstone thesis of clinical BP measurement. However, few studies have confirmed this thesis with direct BP measurements. This study aimed to determine the true differences in aortic and brachial BP by systematic review and meta-analysis of invasive (intra-arterial) data.
Methods: Five online databases and several offline techniques were used to search for studies that reported simultaneous or sequentially recorded intra-arterial aortic and brachial BP. Differences in systolic BP (SBP) and diastolic BP (DBP) were calculated as brachial minus aortic values.
Results: Data from 12 studies (from 1956 to 2013), totalling 399 participants (aged 57.3 [95% CI: 52.2, 62.4] years, 76.9% male) met inclusion criteria. Brachial SBP was significantly higher than aortic SBP (pooled SBP difference estimate = 7.99 [95% CI: 5.30, 10.7] mmHg, p<0.001; I2 = 93.3%). However, there was only a minimal decrease in DBP between the aorta and brachial artery (pooled DBP difference estimate = −0.67 [95% CI: −1.67, 0.32] mmHg, p = 0.18; I2 = 79.7%). Heterogeneity in SBP differences between studies was modestly explained by age (R2 = 5.7%), but not by sex, measurement method (simultaneous or sequential) or type of catheter (fluid-filled or micromanometer [R2 = 0% all]).
Conclusion: Although only minimal difference in DBP, brachial SBP is significantly higher than aortic SBP, with substantial variability in the magnitude of SBP difference. This questions the Riva-Rocci assumption of brachial BP being representative of aortic BP, and could have accuracy implications for BP assessment using the brachial cuff method.
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