An automatic method for categorizing heartbeats using two or more selected ECG signals, the method comprising, when a heartbeat has been detected, the steps of: (a) determining a signal velocity for each selected signal at a categorization fiducial time tC within the detected heartbeat； (b) forming a vector F(tC) having as its components the velocities of each of the selected signals at time tC； (c) determining the angle between the vector F(tC) and a previously-stored template vector； (d) comparing the angle with a threshold angle； and (e) if the angle is less than the threshold angle, categorizing the heartbeat as similar to a heartbeat which corresponds to the template vector.
