A patient monitoring device (20) employing an ECG monitor (24) and a controller (26). The patient monitoring device (20) can be or include an automatic external defibrillator (AED), an advanced life support (ALS) defibrillator and/or a patient monitor. In operation, the ECG monitor (24) monitors a corrupted ECG waveform (30) of a heart of a patient, and the controller (26) classifies the corrupted ECG waveform (30) as one of a non-shockable rhythm or a potentially shockable rhythm. The corrupted ECG waveform (30) is classified by the controller (26) as the non-shockable rhythm responsive to detection by the controller (26) of a presence of an asystole rhythm within the corrupted ECG waveform (30). Conversely, the corrupted ECG waveform (30) is classified by the controller (26) as the potentially shockable rhythm responsive to a detection by the controller (26) of an absence of the asystole rhythm within the corrupted ECG waveform (30) and/or an indetermination by the controller (26) as to the presence of the asystole rhythm within the corrupted ECG waveform (30).
