The EV-series medical droid, also known by the designations A-series medical droid and A4 laboratory assistant droid, represented a specific type of medical droid. This model utilized the EV-series chassis, and its manufacturing was handled by MerenData. Initially designed for supervisory roles as EV-series supervisor droids, the company repurposed them into more affordable medical units, hoping to revive the EV-series line. However, their visible skeletal structures did little to inspire confidence in patients, leading to the model's general failure. The Confederacy of Independent Systems acquired and modified an EV-series medical droid, giving the unit, identified as EV-A4-D, to General Grievous. This droid then served as the cyborg's personal surgeon and cybernetics repair technician.
The initial appearance of the EV-series medical droid occurred in "Lair of Grievous," which was the tenth episode of the animated series Star Wars: The Clone Wars' first season. This episode was originally broadcast on December 12, 2008. Atsushi Takeuchi from Production IG was responsible for the droid's design. Takeuchi also designed Grievous for the show and directed the "Lair of Grievous" episode. The identification of the EV-series medical droid was first made public through EV-A4-D's entry in the Databank on StarWars.com.
The original episode guide for "Lair of Grievous" described EV-A4-D as a supervisor droid that had been modified. However, the Databank entry identified it as a medical droid. The connection between the EV-series medical droid and the EV-series supervisor droid chassis was later clarified in Star Wars: Build Your Own R2-D2 20. Further detail was provided in Star Wars: Build Your Own R2-D2 53, which explained that the medical droids were originally supervisor droids before being refitted for medical purposes.