Defining the Risk of Ventricular Tachycardia in Genetic Forms of Early-onset Atrial Fibrillation

This study is investigating the risk of dangerous heart rhythm problems (ventricular tachycardia) in people who developed atrial fibrillation (an irregular heart rhythm) early in life and carry a genetic variant linked to heart muscle disease. **You may be eligible if...** - You are 18 years or older - You were diagnosed with atrial fibrillation before age 60 - You are scheduled for a catheter-based ablation procedure for your AF (first-time or repeat) - You have a genetic variant in the TTN gene or another cardiomyopathy-related gene, OR you have been confirmed not to carry such a variant (as a control participant) - You are able to provide written informed consent **You may NOT be eligible if...** - You were diagnosed with a genetic heart muscle disease or arrhythmia syndrome before your AF diagnosis - You have a pacemaker or implantable defibrillator (ICD) - You have had a prior procedure for a different type of dangerous heart rhythm - You have severely reduced heart function (ejection fraction below 20%) - You have a prosthetic mitral or aortic valve, heparin allergy, or prior heart attack Talk to your doctor to see if this trial is right for you.