A method and system for atrial defibrillation in a patient are provided. The method comprises introducing into the patient a catheter comprising an elongated catheter body having proximal and distal ends and at least one lumen therethrough, and a basket-shaped electrode assembly at the distal end of the catheter body. The electrode assembly has proximal and distal ends and comprises a plurality of spines connected at their proximal and distal ends, each spine comprising an elongated spine electrode along its length. The electrode assembly has an expanded arrangement wherein the spines bow radially outwardly and a collapsed arrangement wherein the spines are arranged generally along the axis of the catheter body. The method further comprises introducing the electrode assembly into the heart of the patient and applying defibrillation energy to the tissue through one or more of the elongated electrodes. The system comprises a catheter as described above in combination with an external defibrillator electrically connected to the catheter.