2.8: Invasive Study for Testing Non-Invasive Methods of Aortic Pressure Estimation

Abstract

Purpose

Aortic blood pressure has a superior prognostic value with respect to the brachial pressure [1]. Nonetheless, the low efficacy of the most used non-invasive methods (i.e., approaches based on the generalized transfer function (GTF)) may hamper the detection of this superiority in population studies [2]. In this sense, low-order, patient-specific whole-body mathematical models might help to bridge brachial to aortic pressure waveforms. We aimed to compare (i) GTF, (ii) a patient-specific 1D-0D mathematical model, and (iii) brachial blood pressure in the estimation of invasive aortic pressure measured through catheter.

Method

One-hundred patients referred to diagnostic coronary angiography were included in this study. Brachial pressure was measured with a validated automatic oscillometric device simultaneously to invasive aortic pressure, which was measured with a calibrated fluid-filled catheter. End-systolic and end-diastolic left ventricular volumes, carotid-femoral pulse wave velocity and tonometric radial waveform were measured immediately prior to the invasive procedure and were used to set GTF and the mathematical model.

Results

Oscillometric brachial pressure overestimated both systolic (2.4 ± 12.6 mmHg, R² = 0.71) and diastolic (3.7±9.8 mmHg, R² = 0.48) aortic pressure. GTF method underestimated systolic (9.4 ± 11 mmHg, R² = 0.71 ) and overestimated diastolic (4.5 ± 10.2 mmHg, R² = 0.4) aortic pressure. Mathematical model underestimated both systolic (4 ± 16.5 mmHg, R² = 0.47) and diastolic (3.9 ± 10.4 mmHg, R² = 0.62) aortic pressure. Brachial pressure and GTF methods presented trends toward systolic and diastolic pressure overestimation for higher aortic pressure, while mathematical modeling not.

Conclusions

Systolic and diastolic oscillometric brachial pressures give a better predictor of aortic pressure extremes with respect to both GTF-and mathematical model-based methods.