An apparatus for determining when a patient is susceptible to
defibrillation comprises a plurality of electrodes (12, 14) for obtaining
an ECG signal from a patient, and data processing means (30, 42) for
determining a region of the ECG signal where the signal passes from a
first threshold to a second threshold at least equal in magnitude but of
opposite polarity to the first threshold while the gradient of the signal
remains within certain limits, detecting the next following ECG signal
peak, and providing an output signal upon such detection.
