Local heating induces an increase in the pulse wave velocity in peripheral vessels

Accurate assessment of peripheral microcirculation is of great importance for wide range of clinical applications, from routine clinical examinations to patient monitoring in the operation room. Promising approach for assessing microcirculatory hemodynamics in-vivo is the use of a multimodal system based on synchronized imaging photoplethysmography (iPPG) and electrocardiography (ECG). However, precise estimation of the temporal characteristics of peripheral pulse waves is still a challenging task due to motion artifacts. In this study, we implemented data processing algorithm characterized by an increased signal-to-noise ratio. We analyzed 67 recordings of the microcirculation response in the forearm to local heating measured by the iPPG-ECG system from 47 healthy volunteers. A significant decrease in the pulse arrival time, accompanied by a multiple (up to 23-fold) increase in the pulsation amplitude was observed in all recordings after heating the forearm skin up to 41 °C. For the first time, an increase in the pulse wave velocity in a local peripheral area was detected. We interpret these findings as a consequence of an increase in the lumen of arteriovenous anastomoses in response to local heating. Therefore, the velocity of propagation of the arterial pulse wave is changed not only due to variations in the stiffness of the arterial walls but also because of redistribution of blood flow in the periphery, which is accomplished through the functioning of arteriovenous anastomoses. The advanced multimodal iPPG-ECG technique holds good promise for further in-depth studies of regional and central hemodynamics both in normal and pathological conditions.