Patent ID: 8457726

Claim:
An implantable medical device comprising: an event detector that detects occurrence of a predefined heart event in a detection time window from start of a heart cycle of a heart up to opening of aortic valves in said heart cycle, said detected predefined event is assigned a time reference; an onset detector that detects an onset of ventricular filling of said heart in said heart cycle; a timing processor that determines a relative time of said detected onset of ventricular filling based on said assigned time reference; a heart failure processor that generates detection data indicative of an increased risk of heart failure of a subject based on said determined relative time; a signal applier that applies a current or voltage signal over at least a portion of said heart via two electrodes; a signal measurer that measures a resulting voltage or current signal over between said two electrodes; an impedance processor that determines an impedance signal based on said applied current or voltage signal and said measured resulting voltage or current signal, wherein said onset detector detecting said onset of ventricular filling based on said impedance signal. a time assigner that assigns a zero time reference to said detected predefined event: said timing processor comprising a sample counter that counts a number of samples in said impedance signal from said occurrence of said predefined event up to said onset of ventricular filling; and said timing processor comprising a time converter that determines said relative time of said detected onset of ventricular filling by dividing said counted number of samples with a sampling frequency of said impedance processor.