Implantable medical device (10) comprises: an integrated or connected implantable acceleration sensor； a ballistocardiogram (BCG) detection unit, which is joined or to be connected to the acceleration sensor, which is designed to process a acceleration signal derived from the acceleration sensor and a ballistocardiogram derived from the acceleration sensor output signal； and BCG evaluation unit associated with the BCG detection unit and designed to evaluate a ballistocardiogram originating from the BCG detection unit. Implantable medical device (10) comprises: an integrated or connected implantable acceleration sensor； a ballistocardiogram (BCG) detection unit, which is joined or to be connected to the acceleration sensor, which is designed to process a acceleration signal derived from the acceleration sensor and a ballistocardiogram derived from the acceleration sensor output signal； and BCG evaluation unit associated with the BCG detection unit and designed to evaluate a ballistocardiogram originating from the BCG detection unit and the BCG evaluation unit provides a stroke volume representing a respective output signal.
