One of the main disadvantages of most pacing systems available today is their inability to increase stimulating rate with exercise. This paper describes the concept of an autoregulating pacing system the rate of which is determined by changes in mixed venous oxygen content. For the realization of this concept an optical sensor mounted on the pacing lead has been developed which allows continuous monitoring of the oxygen saturation in the right ventricular cavity. The advantages of this parameter over other physiologic hemodynamic or metabolic variables are discussed.
