Chest x-ray depicting a biventricular cardiac pacing system used for the treatment of cardiac failure. The atrial lead (RA) is in its usual location in the right atrium and the ventricular lead (RV) is in the apex of the right ventricle. The unipolar lead (LV) used for pacing of the left ventricle is guided through the coronary sinus and positioned posteriorly above the left ventricle.