Definitions used in this report:

SSI: A pacemaker that senses and stimulates one chamber at one rate.

AAI: A pacemaker that stimulates and senses the atrium at one rate

VVI: A pacemaker that stimulates and senses the ventricle at one rate

SSI.R A pacemaker that senses and stimulates one chamber at a rate determined by a sensor

AAI.R A pacemaker that senses and stimulates the atrium at a rate determined by a sensor

VVI.R A pacemaker that senses and stimulates the ventricle at a rate determined by a sensor

DDD: A pacemaker that senses and stimulates both atrium and ventricle. The stimulation rate is determined the maximum tracking rate and a minimum rate.

DDD.R: A pacemaker that senses and stimulates both atrium and ventricle. The stimulation rate is governed by a maximum rate, the rate determined by a sensor and the minimum rate.

DDI: A pacemaker that senses and stimulates both atrium and ventricle. The stimulation rate is fixed.

DDI.R: A pacemaker that senses and stimulates both atrium and ventricle. The stimulation rate is governed by a maximum rate, the rate determined by a sensor and the minimum rate.

VDD: A pacemaker that senses the atrium and ventricle and paces the ventricle.