Implantable medical device with improved long-term mode applied in case of atrial tachycardia

Implantable medical device for stimulating a human or animal heart, comprising a processor, a memory unit, a stimulation unit configured to stimulate a human or animal heart, a first detection unit configured to detect an electric signal in an atrium of the same heart, and a second detection unit configured to detect an electric signal in a ventricle of the same heart,

• wherein the memory unit comprises a computer-readable program that causes the processor to perform the following steps when executed on the processor:
• a) repeatedly detecting, with the first detection unit, an atrial electric signal;
• b) repeatedly determining whether the atrial electric signal is indicative for an atrial fibrillation;
• c) if the atrial electric signal is indicative for an atrial fibrillation, switching an operational mode of the implantable medical device from a regular mode to a fibrillation mode, wherein the fibrillation mode exclusively allows a ventricular controlled stimulation of a ventricle of the heart to be stimulated, wherein at least one additional function that uses information from the right atrium, when the right atrium is not in an AF state, is deactivated;
• and
• switching the operational mode of the implantable medical device from the fibrillation mode to an atrial-fibrillation optimized long-term mode, if a switching criterion is fulfilled;
• wherein the atrial-fibrillation optimized long-term mode exclusively allows a ventricular controlled stimulation of the ventricle of the heart to be stimulated, wherein the at least one additional function that was deactivated in the fibrillation mode is reactivated.