Hardware detection of P-waves in the electrocardiogram.

Abstract

A reliableP-wave detector has been designed for use in experiments where the firing of the sino-atrial node is important. Unlike other circuits which require tripolar electrodes implanted in the atrial myocardium this device will operate with either Lead II or III of the bipolar e.c.g. and utilises the q.r.s. complex as a time reference. Various analogue techniques are used to preprocess, filter and differentiate the reference signal to enhance the shape and the signal/noise ratio of theP-wave. Detection of theP-wave is only carried out over a portion of the cardiac cycle determined by inhibition windows whose duration is made proportional to the average interbeat interval. All threshold elements are gated by signals derived from a digital algorithm to limit their operation to portions of the cycle within which the event to be detected is assumed to arrive. The device requires a minimum of adjustment during operation and will operate reliably for heart rates in the range of 30–300 b.p.m. It will also remain stable and automatically reset under all conditions of signal dropout and invalid triggering. Operation to date has demonstrated that detection is relatively insensitive to high-frequency noise, baseline drift or muscle artefact.