Variable threshold R wave detector: use in automated ECG processing.

Reliable R wave detection is difficult under many commonly found conditions of varying baseline and changing morphology such as varying R wave amplitude and reduced R/T ratio. An instrument has been developed which overcomes many of these problems. The device employs a variable detection threshold which is based on the amplitude of the last occurring R wave. For large R wave amplitudes, the threshold is raised, thus providing good noise immunity. For low R wave amplitudes, the threshold is lowered, thus providing continued detection. An R wave filter de-emphasizes noise as well as P and T waves, and an adjustable refractory period following R wave detection prevents false detection during this period. The variable threshold R wave detector has been used to process ECG in a heart rate study in nearly 100 diabetic patients as well as in healthy controls. The detector provides much improved automatic R wave detection over fixed level detectors and can be constructed with parts costing under 100 dollars.