The wireless capabilities of modern Implantable Medical Devices (IMDs) make them vulnerable to security attacks. One prominent attack, which has disastrous consequences for the patient's wellbeing, is the battery Denial-of-Service attack whereby the IMD is occupied with continuous authentication requests from an adversary with the aim of depleting its battery. Zero-Power Defense (ZPD), based on energy harvesting, is known to be an excellent protection against these attacks. This paper raises essential design considerations for employing ZPD techniques in commercial IMDs, offers a critical review of ZPD techniques found in literature and, subsequently, gives crucial recommendations for developing comprehensive ZPD solutions. Keywords Implantable medical device • IMD • Energy harvesting • Wireless power transfer • Zero-power defense • Authentication protocol • Denial-of-service attack • Battery DoS • Battery-depletion attack This work is an extended version of [49], which was presented at the 16th ACM International Conference on Computing Frontiers. This paper improves the original article by (1) introducing additional design considerations in Section 4, (2) adding nonharvestingbased-ZPD works in Section 5, (3) discussing the impact of electromagnetic-noise attacks on IMDs in Section 6.2, and (4) proposing the novel concept of a standalone ZPD module along with the taxonomy of ZPD implementations in Section 6.