The family of Edward Harrigan -- a patient who died at Tobey Hospital in Wareham after no one responded to warnings on his cardiac monitor -- filed a federal lawsuit against the hospital and a nurse this week. Harrigan, 87, was a patient at the hospital in September 2008. His electrocardiogram displayed a "flat line" for more than two hours because the battery in his heart monitor had died, but no one changed the battery, according to state Department of Public Health investigators. During that time, his heart stopped. Because the monitor was not working, no alarm sounded to alert staff to his cardiac arrest. They later found him unresponsive and without a pulse. The family's attorney said yesterday that Harrigan's death was caused by alarm fatigue -- when nurses become desensitized to monitor alarms, both audible and visual.