Abstract: A medical system for performing a tissue ablation procedure comprises a guide sheath and an ablation catheter disposed within an internal lumen of the catheter. The guide sheath has a distal end that includes irrigation exit ports that are configured to perfuse irrigation fluid in a distal direction over the ablation electrode of the catheter when the distal end of the catheter protrudes from the guide sheath. In this manner, the ablation electrode can be advantageously cooled during the tissue ablation process, thereby maximizing the size and depth of the ablation lesion and reducing the duration of the ablation process.