An apparatus, comprising: a first shaft defining a longitudinal axis and a lumen; and a second shaft disposed within the lumen and having a distal portion that extends from a distal end of the first shaft; a plurality of electrodes (3932, 3934); a set of splines, each spline of the set of splines including: a set of electrodes from the plurality of electrodes (3932, 3934) formed on that spline, each set of electrodes including a distal electrode such that the set of splines includes a set of distal electrodes and a proximal electrode such that the set of splines includes a set of proximal electrodes; a proximal end coupled to the distal end of the first shaft; and a distal end coupled to a distal end of the second shaft, the set of splines transitionable into a plurality of states between and inclusive of an undeployed configuration and an expanded configuration in which a distal portion of each spline from the set of splines is set at one of a corresponding plurality of angles relative to a proximal portion of each spline from the set of splines in each of the plurality of states, a pre-selected portion of the plurality of electrodes (3932, 3934) activatable in each of the plurality of states to generate an electric field for ablating a tissue wall by irreversible electroporation; wherein the first shaft is a first inner shaft and the second shaft is a second inner shaft, the apparatus further comprising an outer shaft, wherein the first inner shaft and the second inner shaft are configured to slide relative to the outer shaft. a first shaft defining a longitudinal axis and a lumen; and a second shaft disposed within the lumen and having a distal portion that extends from a distal end of the first shaft; a plurality of electrodes (3932, 3934); a set of splines, each spline of the set of splines including: a set of electrodes from the plurality of electrodes (3932, 3934) formed on that spline, each set of electrodes including a distal electrode such that the set of splines includes a set of distal electrodes and a proximal electrode such that the set of splines includes a set of proximal electrodes; a proximal end coupled to the distal end of the first shaft; and a distal end coupled to a distal end of the second shaft, a set of electrodes from the plurality of electrodes (3932, 3934) formed on that spline, each set of electrodes including a distal electrode such that the set of splines includes a set of distal electrodes and a proximal electrode such that the set of splines includes a set of proximal electrodes; a proximal end coupled to the distal end of the first shaft; and a distal end coupled to a distal end of the second shaft, the set of splines transitionable into a plurality of states between and inclusive of an undeployed configuration and an expanded configuration in which a distal portion of each spline from the set of splines is set at one of a corresponding plurality of angles relative to a proximal portion of each spline from the set of splines in each of the plurality of states, a pre-selected portion of the plurality of electrodes (3932, 3934) activatable in each of the plurality of states to generate an electric field for ablating a tissue wall by irreversible electroporation; wherein the first shaft is a first inner shaft and the second shaft is a second inner shaft, the apparatus further comprising an outer shaft, wherein the first inner shaft and the second inner shaft are configured to slide relative to the outer shaft.