Improvement of an algorithm for the detection of augmentation point from the aortic pressure waveform

Aortic AIx(augmentation index) has been used to measure aortic stiffness quantitatively and even to evaluate ventricular load. Due to its advantage, aortic AIx has a special attention for the measurement of arterial stiffness. In this study, an algorithm which detects dicrotic notch and augmentation point for the calculation of AIx were developed. Algorithm for the detection of dicrotic notch and augmentation point gradually increases the differential order to detect inflection point rather than detects the distinctive point that appears after a specific time. For the detection of an augmentation point which appears before the systolic peak, detection range was set between peaks of the first derivative and systolic peak. Also, the detection was performed between systolic peak and dicrotic notch for an augmentation point appears after the systolic peak. Detection range for the dicrotic notch was set between systolic peak and two-thirds period of the whole waveform. Evaluation of an algorithm for the detection of dicrotic notch and augmentation point were performed by comparing the augmentation points obtained from developed algorithm with the known augmentation points of the synthesized waveforms. Developed algorithm for AIx is proved to provide more accurate results than the ones developed by previous studies with the deviation from -11.5±14.34 points to -3.75±1.26 points. Results could provide the basis for the measurement of aortic stiffness using easily-measurable radial artery pulse waves, and could be extended to develop a system for early diagnosis of various vascular diseases.