A pilot study of photoplethysmographic peripheral pulse transit times in paediatric heart transplant recipients and healthy children

Previous studies have demonstrated increased arterial stiffness (AS) in paediatric heart transplant recipients (HTR) by using established SphygmoCor technology. The aim of this study was to assess pulse transit times at three different peripheral body sites in HTR, and in comparison to healthy controls, by using relatively low-cost and easy-to-perform photo plethysmography (PPG) technology. PPG waveforms and an electrocardiography timing reference were recorded from 12 HTR (age range 8-17 years; 5 males) and 30 healthy children (age range 8-16 years; 15 males) from the right and left ear lobes, index fingers, and great toes. The median values for pulse transit times to PPG-pulse foot (PTTj) were calculated over a period of 60 heart beats, with right and left sides averaged at each segmental site. Toe PTTf was significantly shorter in HTR (median 290 ms) compared to controls (324 ms, p <; 0.05). No significant differences were found for ear and finger PTTj Furthermore, toe PTTf significantly correlated with subject height both in HTR (ρ = 0.78, p <; 0.01, slope = 88 ms/m) and controls (ρ = 0.76, p <; 0.001, slope = 132 ms/m). A shorter PTTf at the toe site is consistent with increased AS in paediatric heart transplant recipients and the results from correlation analysis further corroborated this finding.