A head-to-head comparison of pulse transit time using second-derivative and intersecting tangents methods

Objective: Determination of aortic stiffness as measured by carotid-femoral pulse wave velocity (CFPWV) is based on pulse transit time (PTT). PTT is determined by identification of the foot of the pressure wave using either the peak of the second-derivative or the intersecting tangents algorithm. The aim of this study was to examine if there are any differences when these algorithms are performed on the same arterial pressure waveforms. Design and method: Carotid and femoral arterial pressure waveforms were simultaneously recorded using the piezoelectric sensors of the Complior Analyse system. Waveforms were extracted and imported into In-house software (MATLAB; MathWorks, Natick, Massachusetts, USA) to calculate the PTT only on valid pressure waveforms without artifacts that are due to movements. Results: In 105 human subjects (59 ± 18 years; 64% men) including a mix of 59% hypertensive, 34% with chronic kidney disease, 16% diabetic and 13% with cardiovascular disease, the average brachial blood pressure was 125 ± 18/73 ± 10 mmHg. A total of 6 203 pairs of simultaneous carotid and femoral arterial pressure waveforms were analysed. The PTT using the second-derivative algorithm was 68.4 ± 18.6 ms (CFPWV: 9.48 ± 3.18 m/s), similar to PTT using the intersecting tangents method that was 68.6 ± 18.8 (CFPWV: 9.45 ± 3.12). This difference while statistically significant given the high number of observation points (P < 0.001), is not considered to be clinically significant. Conclusions: Based on our findings, both algorithms perform similarly and can be used interchangeably when high quality acquisition are used. However, device-based algorithms may perform differently given variabilities in quality assessment criteria.