An enhanced method and device are provided to inhibit or reduce restenosis following angioplasty or stent placement. A porous balloon-tipped catheter is disposed in the area treated or opened through balloon angioplasty immediately following angioplasty. The balloon, which can have a dual balloon structure, may be delivered through a guiding catheter and over a guidewire already in place. A fluid such as a perfluorocarbon flows into the balloon to freeze the tissue adjacent the balloon, this cooling being associated with reduction of restenosis. A similar catheter may be used to reduce atrial fibrillation by inserting and inflating the porous balloon such that an exterior surface of the balloon, as well as a portion of the cold working fluid, from the microporosity contacts at least a partial circumference of the portion of the pulmonary vein adjacent the left atrium.