A method for determining local pulse wave velocity in human ascending aorta from sequential ultrasound measurements of diameter and velocity

Abstract

Background: Pulse wave velocity (PWV) is an indicator of arterial stiffness, and predicts 2 cardiovascular events independently of blood pressure. Currently, PWV is commonly measured by the foot-to-foot technique thus giving a global estimate of large arterial stiffness. However, and despite its importance, methods to measure the stiffness of the ascending aorta are limited. Aim: To introduce a method for calculating local PWV in the human ascending aorta using noninvasive ultrasound measurements of its diameter (D) and flow velocity (U). Methods: 10 participants (4 females) were recruited from Brunel University students. Ascending aortic diameter and velocity were recorded with a GE Vivid E95 equipped with a 1.5-4.5MHz phased array transducer using M-mode in the parasternal long axis view and pulse wave Doppler in the apical 5 chamber view respectively. Groups of 6 consecutive heartbeats were selected from each 20s run based on the most similar cycle length resulting 3 groups for D and 3 for U each with 6 waveforms. Each D waveform was paired with each U waveform to calculate PWV using ln(D)U-loop method. Results: The diastolic portions of the diameters or velocities waveforms were truncated to allow the pairs to have equal length and were used to construct ln(D)U-loops. The trimmed average, excluding 10% of extreme values, resulting from the 324 loops was considered representative for each participant. Overall mean local PWV for all participants was 4.1(SD = 0.9)m/s. Conclusions: Local PWV can be measured non-invasively in the ascending aorta using ultrasound measurements of diameter and flow velocity This should facilitate more widespread assessment of ascending aortic stiffness in larger studies.