Apparatus is provided including an implantable sensor, adapted to sense an electrical parameter of a heart of a subject, and a first control unit, adapted to apply pulses to the heart responsively to the sensed parameter, the pulses selected from the list consisting of: pacing pulses and anti-arrhythmic energy. The apparatus further includes an electrode device, adapted to be coupled to a site of the subject selected from the list consisting of: a vagus nerve of the subject, an epicardial fat pad of the subject, a pulmonary vein of the subject, a carotid artery of the subject, a carotid sinus of the subject, a coronary sinus of the subject, a vena cava vein of the subject, a right ventricle of the subject, and a jugular vein of the subject; and a second control unit, adapted to drive the electrode device to apply to the site a current that increases parasympathetic tone of the subject and affects a heart rate of the subject. The first and second control units are not under common control. At least one of the control units is adapted to coordinate an aspect of its operation with an aspect of operation of the other control unit. Other embodiments are also described.