Delores Smith was a former patient of House. She was an unseen character.
Delores had a heart condition. Normally, she would have been given nitroglycerine. However, she also had low blood pressure and since nitroglycerine quickly dilates the blood vessels, using it would be dangerous.
Instead House prescribed Viagra, which acts much more slowly to the dilate the blood vessels. He then billed the matter to Medicare and thought nothing more of it.
However, House's Medicare billings were all for top complexity cases and drew scrutiny. He had to go to Baltimore, accompanied by Stacy Warner, to meet a Medicare review officer, Peter Foster, who challenges House's treatment. House, angered by someone questioning his off-label use, offers to pay for the pills himself. Luckily, Stacy intervenes and points out House's medical decision was valid.