A method is provided for ablation in treatment of heart arrhythmias such as atrial fibrillation that includes positioning a catheter apparatus with multiple electrodes within a cardiac chamber, visualizing the catheter apparatus with an interventional system, navigating the catheter apparatus within the cardiac chamber, and delivering energy to selected electrodes of the catheter apparatus from an external source to ablate heart tissue at select locations. Preferably, the external source is an external patch placed on the patient for the delivery of radio-frequency energy. The electrodes of the catheter apparatus are connected to the patch through a patient interface unit where the interface unit selects the electrodes to which radio-frequency energy is to be delivered. In another aspect of the invention, a system for ablation of heart arrhythmias is provided that has a catheter apparatus with multiple electrodes, an interventional system for visualizing the catheter apparatus within a cardiac chamber, and an external source for delivering energy to selected electrodes of the catheter apparatus within the cardiac chamber to ablate heart tissue. Preferably, the system further includes a digital imaging system for obtaining cardiac image data, an image generation system for generating a 3D model of the cardiac chamber from the cardiac image data, and a workstation for registering the 3D model with the interventional system and for visualizing the catheter apparatus over this registered 3D model upon the interventional system.