The present invention provides a method of manufacturing a plurality of high L / d internal fluid passages and / or slit-shaped (or elliptical) passages to provide a more uniform distribution of flow rates and flow rates over the outer surface of the electrode, Of an irrigation type ablation electrode. In some embodiments, the slit-shaped opening has an aspect ratio of at least 3, at least 5, at least 10, or at least 15. Some embodiments provide an irrigated ablation electrode having an irrigation fluid flow rate of at least 345 (5 ml / min) between an irrigation fluid inside the irrigated ablation electrode and the fluid immediately outside the irrigation ablation electrode, when the irrigation fluid has a flow rate of less than 5 milliliters Including maintaining pressure drop in Pascal. Some embodiments include a low density insert and have multiple fluid channels on its outer surface to more efficiently cool the electrode and provide a faster thermal response.(FIG.
