An infusion catheter having a distal shaft with an infusion tube extending from a proximal end to a distal end of the distal shaft, and a proximal cannula with an inner dimension and a distal end attached to a proximal end of the distal shaft to define an opening between the inner diameter of the infusion tube and the inner dimension of the proximal cannula. Also, a guidewire tube disposed within the inner dimension and the distal shaft and extending from the proximal end of the proximal cannula to the distal end of the distal shaft. The inner diameter of the infusion tube, the opening, the exterior dimension of the guidewire tube and the inner dimension cooperate and define sufficient cross sectional sizes to allow a treatment agent to be infused between the proximal end of the proximal cannula and the region of interest.