A catheter assembly for treatment of cardiac arrhythmia. The catheter assembly includes a catheter body and an ablative energy source. The catheter body includes a proximal portion, an intermediate portion, and a distal portion. The intermediate portion extends from the proximal portion and defines a longitudinal axis. The distal portion extends from the intermediate portion and includes an ablation section and a tip. The ablation section forms a loop defining a diameter greater than an outer dimension of a pulmonary vein ostium. The tip extends distally from the ablation section and is configured to locate a pulmonary vein. Finally, the ablative energy source is associated with the ablation section. With this configuration, upon activation of the energy source, the ablation section ablates a desired lesion pattern. In one preferred embodiment, the ablation section forms a distally decreasing radius helix, whereas the tip includes a relatively linear leader section. With this one preferred configuration, the tip readily locates a pulmonary vein and guides the ablation section to a seated relationship about a pulmonary vein ostium (or extra-ostial).