Anti-tachycardia pacing for low power implantable medical devices

An implantable medical device, comprising:

• a housing coupled to electrodes;
• a power source within the housing;
• memory, within the housing, to store storing program instructions;
• a sensing circuit to sense cardiac signals from the electrodes, the cardiac signals representative of a ventricular tachycardia (VT) episode that includes at least a select number of VT events having corresponding VT cycle lengths;
• and
• one or more processors within the housing, wherein, responsive to execution of the program instructions, the one or more processors:
• analyzing the VT cycle length to define an anti-tachycardia pacing (ATP) therapy that includes a first coupling interval;
• delivering a first ATP pulse that is spaced the coupling interval after a reference refractory VT event sensed at the electrodes;
• and
• delivering a second ATP pulse following the first ATP pulse by a non-stimulation segment that is at least one and three-quarters (1.75) times a projected VT cycle length.