A method and balloon catheter apparatus for tissue ablation is disclosed. The apparatus comprises an elongated shaft having a proximal end, a distal end, one or more central lumens, adapted for positioning in an artery; an emitter capable of emitting microwave energy positioned at the distal end; an inflatable balloon associated with the emitter at the distal end configured to allow blood to pass through the artery while the balloon is inflated; and a control system at the proximal end. The method and balloon catheter apparatus is applicable at least to renal denervation procedures.