Devices and methods for tissue ablation include injecting a conductive medium into a target tissue and then delivering an ablative agent to the conductive medium to ablate the target tissue. Ablation catheters also include multiple inline chambers for the containing and heating of an ablative agent. The heating chambers include multiple channels to increase the contact surface area of the ablative agent with the walls of the heating chamber to provide more efficient heating. Induction heating is used to heat a chamber and vaporize a fluid within by wrapping a coil about a ferromagnetic chamber and providing an alternating current to the coil. A magnetic field is created in the area surrounding the chamber which induces electric current flow in the chamber, heating the chamber and vaporizing the fluid inside.