An implantable system applies tiered antitachycardia pacing (ATP) that may be combined with pre-pulsing therapy in order to reduce pain. In one implementation, an exemplary system applies a progression of increasingly potent pacing vectors, progressing in an initial tier from small electrodes inside the heart to later tiers that increasingly use a large electrode surface outside the heart. In the latter tiers, a pre-pulse may be added prior to each ATP pulse to reduce the sensation of pain.