Development of a coding system for pacemakers.

Since the establishment of the first pacemaker coding system (The Three-Letter Code, 1974) with its nine different pacemaker modes, the number of available modes has increased remarkably. As a consequence, even the expanded "Five-Letter-Code" is no longer adequate to describe the different modes with sufficient precision. To overcome these difficulties, we tried to construct a coding system that represents each mode in a pictorial form, which is simultaneously and precisely defined by a schematic circuit and a number within a numerical matrix.