Sensor and control technology for cardiac pacing

Pacemakers are implanted on account of deficiencies in rhythm generation and excitation conduction in the heart. The aim of sensor-controlled pacemaker systems is, apart from the preservation of life, the greatest possible restoration of physiological adaptation to circulatory stress. If the intrinsic rhythm generator breaks down, this cannot be achieved ideally by a technical shunt, but approximately by sensing physical and/or physiological variables suited to heart rate control. The latter leads both to feedforward control systems and to feedback (closed) control loops. After an overview on existing sensors the authors offer two new sensor technologies for closed-loop systems which are optimally suited to restore the original physiological control loop to the utmost extent. One uses sensors measuring the atrio-ventricular delay in the heart (dromotropic pacemaker), and the other uses a fibre optic sensor measuring the contraction of the heart (inotropic pacemaker).