Is your heart rate target too high? new study aims to find out

This study looks at how well the heart works during exercise in people who have both atrial fibrillation (an irregular heartbeat) and heart failure. Researchers want to see if the current standard of allowing a resting heart rate of 100-110 beats per minute is too high and harms quality of life. About 40 adults will do treadmill tests and have blood drawn before and after either a cardioversion (electric shock to reset the heart) or a pacemaker plus ablation procedure. The goal is to gather information to improve future care, not to test a new treatment.