1. An ablation method for ablating target tissue within a carotid septum of a patient, the method comprising: endovascularly advancing an ablation device into an artery of the patient, the ablation device comprising first and second arms, the first arm including a first ablation element and the second arm including a second ablation element; contacting the first ablation element with an external carotid artery at a wall location that delimits the carotid septum; contacting the second ablation element with an internal carotid artery at a wall location that delimits the carotid septum; and ablating target tissue within the carotid septum using the first and second ablation elements while the first and second ablation elements are simultaneously contacting the respective carotid arterial walls delimiting the carotid septum.