An ablation catheter comprises an elongate catheter body and a branch electrode element. The elongate catheter body has a central axis, a distal end, and a proximal end. The elongate catheter body is configured to be steered within a heart chamber. The branch electrode element has a base end and a working end or tip. The base end is secured to the elongate catheter body at a location spaced proximally of the distal end and an effector on the working end. The branch electrode element is configured to evert when the distal end of the elongate catheter body is in a pulmonary vein ostium or os so that the effector can be selectively engaged against locations surrounding the pulmonary vein os which differ in radial direction and distance. One or more of linear or curved ablation patterns are generated on tissue adjacent the pulmonary vein os with the effector.
