Cardiac catheters, including a lasso catheter, are provided for use in a system for electrical mapping and ablation of the heart has an array of raised, circumferential ring bump electrodes wherein each circumferential electrode has multiple perforations, which are in fluid communication with a cavity or chamber formed under the surface of the circumferential ring. The cavity is formed 360° around the outer surface or loop lumen of the lasso segment of the catheter which is in fluid communication with a breach hole (or holes) drilled through loop lumen and in fluid communication with an irrigating lumen. Each circumferential ring has a breach hole (or holes) that range from smaller to larger from the proximal end of the loop segment to the distal end of the loop segment in one embodiment.
