Ablation catheter assembly having a virtual electrode comprising portholes

An ablation catheter for ablating tissue, the ablation catheter comprising

• a catheter shaft comprising
• a proximal portion;
• a distal portion, said distal portion being adapted to be inserted into a body cavity having tissue to be ablated and being disposed remotely from said proximal portion, said distal portion comprising an active region including a plurality of portholes including a most-proximal porthole, a most-distal porthole, and an intermediate porthole therebetween, wherein said portholes are adapted to deliver a conductive fluid medium to the tissue to be ablated, wherein a relative size of said portholes changes from a first size of said most-proximal porthole to a second size of said most-distal porthole, wherein said intermediate porthole is a third size different from said first size and said second size, and wherein said portholes are circular in cross section and a relative diameter of said portholes increases in size as one moves distally from said most-proximal porthole to said most-distal porthole;
• and
• a first lumen extending from said proximal portion to said distal portion, said first lumen being adapted to carry the conductive fluid medium from said proximal portion to said plurality of portholes along said active region of said distal portion;
• and
• a metal electrode mounted within said first lumen and extending along said active region of said distal portion, wherein said metal electrode is adapted to supply ablation energy to the conductive fluid medium.

An ablation catheter for ablating tissue, the ablation catheter comprising:

• a catheter shaft, said catheter shaft comprising:
• a proximal portion;
• a distal portion, said distal portion being adapted to be inserted into a body cavity having tissue to be ablated and being disposed remotely from said proximal portion, said distal portion comprising an active region including a plurality of portholes including a most-proximal porthole, a most-distal porthole, and an intermediate porthole therebetween, wherein said portholes are adapted to deliver a conductive fluid medium to the tissue to be ablated, wherein said portholes are of varying cross-sectional area;
• and
• a first lumen extending from said proximal portion to said distal portion, said first lumen being adapted to carry the conductive fluid medium from said proximal portion to said plurality of portholes along said active region of said distal portion;
• and
• a metal electrode mounted within said first lumen and extending along said active region of said distal portion, wherein said metal electrode is adapted to supply ablation energy to the conductive fluid medium.