A circuit and method for detecting cardiac rhythm abnormalities employ unipolar
signals respectively obtained from a cardiac lead having a tip at which a number
of separate electrodes are disposed, the electrodes being simultaneously in contact
with cardiac tissue. The respective unipolar signals which are obtained from the
multiple electrodes exhibit a time relationship relative to each other, and this
time relationship is analyzed to determine whether a cardiac rhythm abnormality
is present or one or more of the unipolar signals is compared to a template which
is known to represent a cardiac abnormality. Analysis of the time relation is undertaken
by determining the absolute value of a time offset between any two of the unipolar
signals, or by correlating any two of the unipolar signals.