Endocardial Mapping With the CoreMap EP Mapping System

This study is evaluating a new mapping system (called CoreMap EP) that helps doctors identify the abnormal electrical patterns in the heart that cause atrial fibrillation (AFib) — an irregular heartbeat. The system is used during a standard AFib ablation procedure (a treatment that destroys the tissue causing the abnormal rhythm). **You may be eligible if...** - You are between 18 and 80 years old - You have persistent or long-standing persistent atrial fibrillation (AFib that does not stop on its own) - You are already scheduled for a clinically recommended AFib ablation procedure - You are able to give written informed consent **You may NOT be eligible if...** - You have a different type of AFib (e.g., paroxysmal AFib, which comes and goes) - You are not scheduled for an ablation procedure - You have conditions that make ablation unsafe - You are outside the age range Talk to your doctor to see if this trial is right for you.