A Johnson & Johnson unit released study data yesterday showing that its catheter-based system might be more effective than drugs are at resolving heart arrhythmias. The company's Biosense Webster unit is hoping to gain FDA approval to market the device for the treatment of atrial fibrillation, making it the first approved device to treat the condition. AtriCure , Boston Scientific, Medtronic and St. Jude Medical all have competing devices, but none have received FDA approval for the condition to date. Report