A monitoring device (7) operates an input block (30) to acquire a pressure signal from a pressure sensor (6a-6c) in an apparatus for extracorporeal blood processing connected to the vascular system of the subject. A processing block (34) repeatedly processes the pressure signal for generation of a time-sequence of parameter values indicative of pressure pulsations originating from heartbeats in the subject, and an evaluation block (35) evaluates the parameter values for detection of cardiac arrest and, if cardiac arrest is detected, generates a dedicated alarm signal. To reduce the risk for false positives without increasing the risk for false negatives, the monitoring device (7) may acquire and process more than one pressure signal, and/or perform an initial viability check before the monitoring is initiated to ensure that pressure pulsations originating from heartbeats are detectable in the pressure signal(s), and/or separate the monitoring of the pressure signal(s) into a detection phase performed during regular operation of a blood pump in the apparatus, and a verification phase performed during a temporary shutdown of the blood pump.
