An implantable medical device receives at least one sensor signal representing inter-movement between a basal region of a heart ventricle and a ventricle apex during at least a portion of a systolic phase of a cardiac cycle. A parameter processor calculates a contraction status parameter value based on the at least one sensor signal. This contraction status parameter value represents an elongation of the ventricle following onset of ventricular activation during a cardiac cycle. The contraction status parameter value is stored in a memory as a diagnostic parameter representing a current contraction status of a subjects heart.
