P.048 Aortic Systolic Blood Pressure: Estimation from the Point of Systolic Augmentation in the Digital Artery Waveform

Abstract

Introduction

Central and peripheral blood pressure and waveforms differ due to effects of wave reflection and amplification. Use of a mathematical transform function to predict central pressure remains controversial. It may be possible to estimate central systolic pressure directly from a peripheral waveform. We investigated this during cardiac catheterisation, examining the effects of pacing and nitroglycerin (NTG) on estimation of central systolic pressure from the peripheral pulse.

Methods

Patients undergoing coronary angioplasty (n = 11, aged 48 to 72 years) participated. A Millar SPC-454D or fluid filled catheter was placed in the aortic root and a pacing wire in the right atrium. Peripheral digital arterial waveforms (Finometer) and aortic waveforms were obtained at baseline, during pacing at 20 bpm above resting heart rate and during administration of NTG (10 and 100 mg/min, i.v.).

Results

Pacing and NTG produced marked changes in central and peripheral waveforms, reducing central augmentation index from 40.4±6.2 to 22.6±8.9% and from 40.4±6.2 to 12.7±7.0% for pacing and NTG 100 mg/min respectively (each P < 0.01). At baseline and during all interventions, there was a close correlation between central systolic blood pressure and absolute finger systolic pressure at the point of late systolic augmentation (R = 0.95, P < 0.0001). The mean difference between measured central aortic systolic BP and that estimated from digital pressure was 2.2 mmHg SD 6.2 mmHg.

Conclusions

These data suggest that central systolic blood pressure can be estimated directly from non-invasive finger pressure waveforms even during interventions such as pacing and NTG that produce a marked change in pressure waveforms.