1. An endovascular device, comprising: an elongate body with a proximal end and a distal end; a non-imaging ultrasound transducer on the elongate body; an endovascular electrogram lead on the elongate body in a position that, when the endovascular device is in the vasculature, the endovascular electrogram lead is in contact with blood; a processor configured to receive and process a signal from the non-imaging ultrasound transducer and a signal from the endovascular electrogram lead; and a memory for storing instructions which, when executed by the processor, causes the processor to: calculate one or more blood flow features extracted from the non-imaging ultrasound signal, wherein the one or more blood flow features includes a ratio of a blood flow velocity away from the ultrasound transducer and a blood flow velocity towards the ultrasound transducer; calculate one or more electrogram features extracted from the electrogram signal, wherein the one or more electrogram features includes a P-wave amplitude; and determine a position of the elongate body within the vasculature based on the calculated one or more blood flow features and one or more electrogram features.