Abstract: Apparatus comprises: (a) a longitudinal member (32), having a distal portion (34); (b) a plurality of electrodes (38) disposed on the distal portion of the longitudinal member, such that a first electrode (38a) of the plurality of electrodes is disposed distally along the longitudinal member from a second electrode (38b) of the plurality of electrodes; and (c) a controller (40). The controller comprises an actuator, and circuitry (42) electrically connected to the electrodes via the longitudinal member. The actuator is configured to move the longitudinal member in discrete incremental movements such that for each incremental movement, (i) before the incremental movement the first electrode is disposed in a starting position, (ii) during each incremental movement the actuator moves second electrode toward the starting position, and (iii) at the end of each incremental movement the second electrode is stationary at the starting position.

Abstract: Apparatus and methods are described, including a method for use with tissue of a renal nerve (770) passing longitudinally within a wall of a renal artery (8) of a subject. Using one or more stimulating electrodes (850a, 850b) disposed within the renal artery, the tissue is stimulated by passing a stimulating current through the wall of the renal artery. Using a sensor (26), a rate of change of blood pressure of the subject is sensed, following the start of the stimulation of the tissue. In response to the rate of change, it is decided whether to ablate the tissue, and in response to deciding to ablate the tissue, the tissue is ablated. Other applications are also described.

Abstract: A method is provided, comprising: (1) applying an excitatory current to renal nerve fibers of a subject; (2) determining a change in a parameter of the subject in response to the excitatory current, the parameter being a fastest rate of increase in arterial pressure during a systolic upstroke of an arterial pressure wave of the subject; (3) in response to the change, deciding whether to ablate the renal nerve fibers; and (4) in response to the deciding, applying ablation energy to the renal nerve fibers. Other embodiments are also described.

Abstract: Apparatus is provided, comprising: (a) an elongate member, having a proximal portion and a distal portion; (b) an extracorporeal controller, coupled to the proximal portion of the elongate member, and comprising a user interface and control circuitry; and (c) an effector unit. The effector unit is coupled to the distal portion of the elongate member, defines a longitudinal axis, and has a contracted state and an expanded state. The effector unit comprises a plurality of electrodes, operable by the control circuitry, and disposed circumferentially around the central longitudinal axis of the effector unit; and an ultrasound transducer, operable by the control circuitry. In the expanded state, each electrode is disposed further radially outward from (i) the central longitudinal axis of the effector unit, and (ii) the transducer compared to the contracted state, and the transducer is oriented to direct ultrasound radially outwardly.

Abstract: A catheter (28) has a distal portion that comprises an electrode unit (22) and an ablation unit (24). A control unit (32) is configured: (i) to receive a preliminary blood pressure value (BPV), (ii) to receive a target excited BPV, (iii) to iteratively: (a) drive the electrode unit to apply an excitatory current to nerve of a renal artery (8), (b) receive a detected excited BPV, and (c) alter a value of a property of the excitatory current, until the detected excited BPV crosses a first threshold, and (iv) subsequently, to iteratively: (d) drive the ablation unit to apply ablating energy to the nerve, (e) subsequently, drive the electrode unit to apply a selected excitatory current to the nerve, and (f) receive a detected ablated BPV, until the detected ablated BPV crosses a second threshold. Other embodiments are also described.

Abstract: Apparatus for facilitating ablation of nerve tissue of a subject is provided, comprising (1) an ablation unit, configured to be percutaneously advanced to a site adjacent to a first portion of the nerve tissue; (2) at least one electrode unit, coupled to the ablation unit, and configured to be percutaneously advanced to a site adjacent to a second portion of the nerve tissue, and to initiate unidirectional action potentials in the nerve tissue, such that the unidirectional action potentials propagate toward the first portion of the nerve tissue; and (3) a control unit, configured: (a) to drive the ablation unit to ablate, at least in part, the first portion of the nerve tissue of the subject, and (b) to drive the at least one electrode unit to initiate the unidirectional action potentials by applying an excitatory current to the second portion of the nerve tissue.

Abstract: Apparatus and methods are described, including a method for use with tissue of a renal nerve (770) passing longitudinally within a wall of a renal artery (8) of a subject. Using one or more stimulating electrodes (850a, 850b) disposed within the renal artery, the tissue is stimulated by passing a stimulating current through the wall of the renal artery. Using a sensor (26), a rate of change of blood pressure of the subject is sensed, following the start of the stimulation of the tissue. In response to the rate of change, it is decided whether to ablate the tissue, and in response to deciding to ablate the tissue, the tissue is ablated. Other applications are also described.