A medical device, such as a cardiac pacing device for an animal, includes an intravascular antenna that has a first coil for engaging a wall of a first blood vessel to receive a radio frequency signal. The first coil includes a first winding wound helically in a rotational direction along a longitudinal axis from a first end of the coil to a second end. A second winding that is connected to the a first winding at the second end, is wound helically in the same rotational direction along the longitudinal axis from the second end to the first end. An electronic circuit is implanted in the animal and is connected to the antenna to receive an electrical signal therefrom.