Abstract: A single-pass transvenous lead for atrial sensing and pacing, ventricular sensing and pacing, as well as for ventricular and atrial defibrillation. The lead optimizes the positioning of the electrodes in various patients regardless of variations in these patients' hearts, by enabling independent adjustment of the spacing between various pacing, sensing and defibrillation electrodes, before and after implantation or insertion in the heart. The lead includes an elongated lead body, an outer sheath that extends coaxially with the lead body, and two atrial windows positioned along the outer sheath, adjustable relative to a reference point such as a distal pacing tip. The outer sheath includes an atrial section that is slidably adjustable along the lead body by means of an expandable member.