P1.06 The Accuracy of Central Systolic Blood Pressure Determined from the Second Systolic Peak of the Peripheral Pressure Waveform

Abstract

Central blood pressure may be a better predictor of cardiovascular risk than peripheral blood pressure. The central systolic blood pressure (cSBP) can be estimated from the late systolic shoulder of the radial pulse waveform (pSBP₂).We compared pSBP₂ with cSBP derived by a generalized transfer function in a large cohort of subjects, across a wide age-range. We also compared pSBP₂ with true central SBP (cSBPi) measured by cardiac catheterization.

Non-invasive measurements were made by applanation tonometry using the SphygmoCor device. The aortic pressure waveform was derived from the radial waveform using a validated transfer function. cSBPi measurements were carried out in 38 subjects undergoing diagnostic cardiac angiography, and the radial artery pressure waveform was recorded simultaneously using the SphygmoCor device.

Data from 1,880 subjects aged 18–85 years, yielded 10,269 individual observations. There was a strong correlation (r = 0.99, P < 0.001) and good agreement between pSBP₂ and the derived cSBP (mean difference = 1 ± 4mmHg). However, at lower average values of cSBP and pSBP₂, there was a greater difference between these two variables suggesting bias in the data. There was also a strong correlation and good agreement between cSBPi and pSBP₂ (r = 0.96, P < 0.001,mean difference = 3 ± 4mmHg), and between the derived cSBP and cSBPi (r = 0.74, P < 0.001, mean difference = −3 ± 8mmHg).

pSBP₂ approximates cSBP in a large cohort, across a wide age-range, but this may be inaccurate at low systolic blood pressures. The reason for this bias has not yet been established, and further investigations are required. Until this is resolved, pSBP₂ should be used with caution, particularly in individuals with lower systolic blood pressures.