A New Method for Continuous Monitoring of Central Arterial Stiffness During Stress

The continuous monitoring of arterial stiffness during pharmacological and dynamic stress is an intriguing and partially unexplored topic. In this work we present a new method for the continuous assessment of the aortic-to-carotid pulse transit time (PTT), which is inversely proportional to the pulse wave velocity (PWV), the gold-standard for arterial stiffness evaluation. The measurement is based on two cutaneous MEMS accelerometers: the first accelerometer is placed on the chest in mid-sternal precordial region and detects the heart vibrations; the second accelerometer is positioned on the neck and detects the carotid vibrations. The time corresponding to the closure of the aortic valve is found automatically on both the accelerometer signals and the PTT is computed as the difference between the two times. We tested our system by monitoring the pulse pressure transit time variation of 8 healthy volunteers during sublingual GTN administration (25μg). The mean maximal percent variation of the PTT after GTN was 3.84±1.69% (range 1.86–6.48%), that is in accordance with the literature where Wilkinson et al. (2002) showed a reduction of the PWV after GTN administration. In conclusion, we propose a new method which is able to the evaluate the variation of the true central PTT during pharmacological and dynamic stress. With this approach, only the proximal tract of the arterial bed (aorta-to-carotid) is considered: muscular arteries, whose contribution in the evaluation of arterial elasticity is usually poor, are excluded.