An example medical device system includes an implantable medical lead including a first defibrillation electrode and a second defibrillation electrode, the first and second defibrillation electrodes configured to deliver antitachyarrhythmia shocks, and a pace electrode disposed between the first defibrillation electrode and the second defibrillation electrode, the pace electrode configured to deliver a pacing pulse that generates an electric field proximate to the pace electrode. The medical device system includes a shield configured to be implanted in a patient separately from the implantable medical lead and disposed anterior at least one of the electrodes, wherein the shield is configured to impede an electric field of the electrical therapy in a direction from at least one of the first defibrillation electrode, the second defibrillation electrode, or the pace electrode away from a heart of the patient.