Heart Rhythm (IMAGE) Columbia University Irving Medical Center Caption Many patients with pacemakers and defibrillators don't know how the devices work or what to do when they experience an irregular heart beat. Credit Columbia University School of Nursing Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.