Antitachycardia pacing (ATP) is an ICD therapy often used to treat ventricular tachycardia (VT). If the heart rhythm starts to accelerate, ATP means the ICD will deliver small but quick, low-energy pulses to pull it back. Some patients may feel symptoms of VT, such as dizziness and lightheadedness, but for many, ATP is so fast and painless, they don't even notice the episode. As long as a normal rhythm is restored, no further treatment is needed. How slick is that? ATP is activated at your doctor's discretion.