Devices, systems and methods are disclosed for electrical stimulation of the vagus nerve to treat or prevent disorders in a patient. The devices comprise a handheld device having one or more electrode interfaces for contacting the outer skin surface of a patient, a power source and a signal generator coupled to the electrode/interfaces for applying one or more electrical impulses to a deep nerve within the patient, such as the vagus nerve. The device further comprises a filter situated in series between the signal generator and the electrode/interfaces for filtering out undesired high frequency components of the electrical impulses to create a cleaner, smoother signal. The filter may comprise an electrically conductive medium and/or a low-pass filter between the signal generator and the electrode/interface.
