A catheter may include electrodes for transvascular nerve stimulation. The electrodes may be positioned within lumens of the catheter and aligned with apertures in the outer wall of the catheter. The electrodes may produce focused electrical fields for stimulation of one or more nerves. In one embodiment, the catheter may include a set of proximal electrodes and a set of distal electrodes, and the proximal electrodes may stimulate a patient's left phrenic nerve and the distal electrodes may stimulate a patient's right phrenic nerve.