Cardiac electrical events are detected by comparing signal vectors with pre-determined
classification zones representative of different cardiac events. The signal vector
is generated by sensing the voltages between various combinations of electrodes,
such as A-tip to V-tip, A-tip to A-ring, and A-ring to V-ring. The signal vector
is compared with a set of classification zones corresponding to different events,
such as P-waves, R-waves, T-waves, A-pulses, and V-pulses, to determine whether
the vector lies within any of the classification zones. In this manner, cardiac
events are detected using only the voltages received from the electrodes and no
refractory periods or blanking periods are required to distinguish one event from
another. The classification zones vary from patient to patient and a technique
is provided herein for generating a set of vector classification zones for a particular
patient. Signal vectors corresponding to various unknown cardiac events are generated
by the implanted device and are transmitted to an external device programmer. ECG
signals, generated by a surface ECG detector, are simultaneously received by the
external programmer. The external programmer identifies the cardiac electrical
event corresponding to each signal vector based on the ECG signals and then generates
classification zones for each event type using only the signal vectors corresponding
to the event.
