A method comprises introducing an ablation catheter assembly into a heart chamber of the patient, deploying an ablative loop structure from an elongated shaft of the ablation catheter assembly, placing the ablative loop structure in an expanded geometry, disposing the expanded ablative loop structure on the endocardial tissue around an ostium of a blood vessel extending from the heart chamber, activating the ablative loop structure, thereby creating a circumferential lesion around the ostium of the blood vessel, disposing the ablative shaft distal end, when the ablative loop structure is housed within the elongated shaft, at a target region of the endocardial tissue remote from the ostium of the blood vessel, and activating the ablative shaft distal end, thereby creating another lesion at the target region.