A digital timer for on-line interval measurement

A digital timer suitable for on-line timing of cardiac intervals on a beat-by-beat basis is described in detail. The device expedites the process of on-line data acquisition and analysis of mapping and timing of atrial and/or ventricular multiple data points for electrophysiologic surgery. An unusual feature allows interval measurement between a fixed reference point and varying data points to be expressed as a positive value regardless of whether the data point occurs before or after the reference. This low-cost device is simple to operate and adds versatility to any existing analog recording system.