Application of Computer Techniques to the Detection and Analysis of Spontaneous P-Wave Variations

A small, laboratory-oriented computer, programmed to scan highly amplified electrocardiographic signals in real-time, specifically searches for spontaneous changes in P-wave configuration. The tape-recorded bipolar extremity leads of 71 normal subjects so scanned revealed sustained periods of ectopic atrial beating in 31. There were 18 with a single well-defined ectopic focus, six with double foci, and seven with atrial activity too variable for simple categorization. Random noise was removed from atrial complexes of the classifiable groups by a discriminant procedure which averaged 50 to 100 members of a preselected P-wave family and automatically bypassed all others. The unexpectedly high incidence of variability indicates that normal atrial excitation is commonly an unstable or metastable process. Actual shifts of pacemaker location, variable exit sites from sinoatrial tissue, and preferential conduction pathways through the atria are postulated as possible explanations of the observed behavior. The richly notched configuration of normal P waves suggests that atrial depolarization proceeds through specialized conductive tissue rather than by uniform centrifugal spread.