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 ; a set of splines , each spline of the set of splines including: a set of electrodes from the plurality of electrodes 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 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 ; a set of splines , each spline of the set of splines including: a set of electrodes from the plurality of electrodes 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 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 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 . <EOS>