Evolution of pacing for bradycardias: sensors

A physiological pacing system should be able to restore normal chronotropic response and optimal conduction within and between the atrial and ventricular pacing. Implan-table sensors are initially developed to overcome chronotropic incompetence of the sinus node to exercise and non-exercise requirements. Ideal sensor behaviour includes speed of response, proportionality, specificity, and sensitivity. Sensors can be classified by the method they detect a physiological change: body accelerations, paced QRS, impe-dance and sensors that require special leads. Rate-adaptive pacing is proven to improve exercise capacity and oxygen consumption over fixed-rated pacing, especially during ventricular pacing. Patients with chronotropic incompetence can derive symp-tomatic benefit in the rate-adaptive mode. The latest development involves the use of sensors to monitor heart failure, and to best optimize rate and conduction status in cardiac resynchronization therapy