An electrocardiogram data management system comprising: a first memory portion configured to store ECG data having values corresponding to electrical signals of a heart acquired over time via a plurality of electrodes disposed at different areas of the heart; and a second, removable, memory portion configured to store the ECG data corresponding to the electrical signals; a processing device configured to manage mapping of the ECG data by: performing a mapping procedure including generating map data and one or more maps from the ECG data for display; concurrently storing the ECG data in the first memory portion and the second, removable, memory portion; in response to a request to export the ECG data, stopping the storing of the ECG data in the second, removable, memory portion and synchronizing the ECG data stored in the second, removable, memory portion with the map data while continuing to perform the mapping procedure; importing data comprising values generated by performance of user defined algorithms on the ECG data, stored in the second, removable, memory data which imported values replace values of the map data; and performing the mapping procedure by generating new map data from the new imported values and providing the new map data for displaying a new map. a first memory portion configured to store ECG data having values corresponding to electrical signals of a heart acquired over time via a plurality of electrodes disposed at different areas of the heart; and a second, removable, memory portion configured to store the ECG data corresponding to the electrical signals; a processing device configured to manage mapping of the ECG data by: performing a mapping procedure including generating map data and one or more maps from the ECG data for display; concurrently storing the ECG data in the first memory portion and the second, removable, memory portion; in response to a request to export the ECG data, stopping the storing of the ECG data in the second, removable, memory portion and synchronizing the ECG data stored in the second, removable, memory portion with the map data while continuing to perform the mapping procedure; importing data comprising values generated by performance of user defined algorithms on the ECG data, stored in the second, removable, memory data which imported values replace values of the map data; and performing the mapping procedure by generating new map data from the new imported values and providing the new map data for displaying a new map. performing a mapping procedure including generating map data and one or more maps from the ECG data for display; concurrently storing the ECG data in the first memory portion and the second, removable, memory portion; in response to a request to export the ECG data, stopping the storing of the ECG data in the second, removable, memory portion and synchronizing the ECG data stored in the second, removable, memory portion with the map data while continuing to perform the mapping procedure; importing data comprising values generated by performance of user defined algorithms on the ECG data, stored in the second, removable, memory data which imported values replace values of the map data; and performing the mapping procedure by generating new map data from the new imported values and providing the new map data for displaying a new map.