There is provided an ambulatory system, comprising at least first and secondwearable sensors, for determining pulsetransit time (PTT) between at least a first and at least a second fixedlocation within the cardiovascular system of a subject. The systemcomprises at least a first device, wherein the first device can contact theskin of the subject, the first device being positioned proximateto the first fixed location； and also comprises at least a second device,wherein the second device can contact the skin of the subject,the second device being positioned proximate to the second fixed location Thesystem further comprises a data collection module thatis in communication with the first and second devices. The first device isconfigured to detect a timing cue within the cardiac cycle ofthe subject, and the second device is configured to detect a pulse pressurewave passing through the second fixed location. The datacollection module collects data relating to the transition of the pulsepressure wave passing through the second fixed location, therebyenabling determination of a pulse transit time (PTT) between the first andsecond fixed locations.
