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Active implantable medical devices (AIMD)

Regulatory basis

Active implantable medical devices are governed by Part II of the UK Medical Devices Regulations 2002, which is derived from the former EU Active Implantable Medical Devices Directive 90/385/EEC (AIMDD). Part II operates separately from Part I (general devices) and Part III (IVDs). All AIMDs require full UK Approved Body assessment.

Disclaimer

This site provides general information only and does not constitute legal or regulatory advice. Always consult the official legislation and MHRA guidance before making regulatory decisions.

Definition​

An active implantable medical device (AIMD) under UK MDR 2002 Part II is a device that is:

  1. An active device — depends on a source of electrical energy or any power source other than directly generated by the human body or gravity, and
  2. Intended to be totally or partially introduced, surgically or medically, into the human body, or by medical intervention into a natural orifice, and
  3. Intended to remain after the procedure

All three conditions must be met. A device that is active but not intended to remain (e.g., a temporary surgical drill) is not an AIMD. A device intended to remain permanently but not active (e.g., a hip implant) is not an AIMD — it is a general medical device.

Examples of AIMDs​

DeviceWhy AIMD
Cardiac pacemakerActive (battery-powered), totally implanted, permanent
Implantable cardioverter-defibrillator (ICD)Active (battery-powered), totally implanted, permanent
Cochlear implant (internal component)Active (radio-frequency powered), totally implanted, permanent
Implantable neurostimulator (spinal cord stimulation)Active, totally implanted, permanent
Deep brain stimulator (DBS)Active, totally implanted in CNS, permanent
Implantable drug infusion pumpActive (battery/gas-powered), totally implanted, permanent
Implantable loop recorder (cardiac monitor)Active, totally implanted, permanent
Retinal implantActive, implanted in the eye, permanent
Active hearing implant (middle ear)Active, implanted, permanent

Accessory devices to AIMDs​

Accessories specifically intended to be used with an AIMD — such as external programmers, patient activators, and telemetry wands — may themselves be regulated as medical devices under Part I, at an appropriate classification. The external components of a cochlear implant system (processor, coil) are not AIMDs but are medical devices in their own right.

Part II vs Class III: what is the difference?​

This is a common source of confusion. Both AIMDs (Part II) and Class III general devices (Part I) carry the highest risk and require the most rigorous conformity assessment. However, they are governed by separate Parts of UK MDR 2002 with distinct Schedules:

CharacteristicAIMD (Part II)Class III general device (Part I)
Governing PartPart II, UK MDR 2002Part I, UK MDR 2002
Source directiveAIMDD 90/385/EECMDD 93/42/EEC
Essential RequirementsPart II, Schedule 1Part I, Schedule 1
Classification basisDefinition in Part IISchedule 2, Rule 8 or Rules 9-12
Energy sourceMust be active (battery, RF, etc.)May be active or passive
Must remain after procedureYesNot required
Conformity assessmentPart II, Schedule 3 (Annex II/III equivalent)Part I, Schedule 3

Cardiac pacemakers are AIMDs. Mechanical heart valves are Class III general devices (passive, no energy source). Drug-eluting coronary stents are Class III general devices (passive, local drug effect).

Essential Requirements for AIMDs​

The Essential Requirements specific to AIMDs are in Part II, Schedule 1 of UK MDR 2002. They expand on the general device ERs with requirements specific to the implanted, active nature of these devices:

Design and construction:

  • The device must be designed and manufactured to be safe and perform as intended when implanted and used under the conditions specified
  • Electrical, mechanical, and biological properties appropriate for an implanted device
  • Electromagnetic compatibility — the device must not be adversely affected by reasonably foreseeable electromagnetic interference, and must not cause interference to other devices or equipment
  • Resistance to the conditions of the internal environment (body fluids, temperature, mechanical stresses)

Materials:

  • All materials in contact with tissues, cells, or body fluids must be compatible with biological tissues (biocompatibility requirements to ISO 10993 series)
  • Corrosion resistance of metallic components
  • No leaching of harmful substances

Power source:

  • Battery life and depletion indicator (where applicable)
  • Means for the patient and clinician to know battery status

Software:

  • Software embedded in an AIMD must be validated, including in-situ performance
  • Software changes must be controlled and documented

Explantability:

  • Devices intended to be removable must be designed to allow safe removal

Patient information:

  • Each AIMD must be accompanied by a summary of its technical and functional characteristics, intended purpose, contraindications, and patient-applicable information
  • The implant card (patient implant card) requirements apply

Patient implant cards​

Manufacturers of AIMDs must provide a patient implant card that contains essential information about the implanted device. The patient receives this card at the time of implantation to carry with them. It must include:

  • Device identification (name, model, serial/lot number)
  • Manufacturer name and contact details
  • UKRP details (for non-UK manufacturers)
  • Any conditions or limitations on use (e.g., MRI conditions, contraindications)
  • Unique Device Identifier (UDI) — as UDI implementation progresses in the UK

This requirement mirrors the implant card obligation under EU MDR Article 18 — though the UK MDR 2002 requirement predates the EU MDR and applies via Part II Schedule 1.

Conformity assessment for AIMDs​

All AIMDs require full UK Approved Body involvement — there is no self-declaration route. The conformity assessment procedure under Part II, Schedule 3 of UK MDR 2002 requires:

Route: Full Quality Assurance (Annex II equivalent)

  1. UKAB audits the manufacturer's complete Quality Management System (covering design, manufacture, and final inspection)
  2. UKAB reviews design dossiers for each AIMD
  3. UKAB issues a QMS Certificate and Design Examination Certificates
  4. Manufacturer issues UK Declaration of Conformity
  5. UKCA mark applied

Alternative Route: EC Type Examination (Annex III equivalent) + Production QA

  1. UKAB examines a representative specimen of the AIMD
  2. UKAB issues an EC Type Examination Certificate
  3. Manufacturer ensures all production conforms to the examined type (via UKAB production audit or manufacturer's declaration)
  4. Manufacturer issues UK Declaration of Conformity
  5. UKCA mark applied

The Full QMS route (Annex II equivalent) is strongly preferred for AIMDs, as it provides the most comprehensive oversight of a product category where failure consequences can be life-threatening.

Clinical investigations for AIMDs​

Clinical investigation of AIMDs in human subjects before market authorisation requires specific ethical and regulatory controls:

  • MHRA notification of clinical investigation intent (for higher-risk pre-market investigations)
  • Ethics Committee approval (via NHS REC system in the UK)
  • Adequate pre-clinical data package (bench testing, animal studies) before first-in-human use
  • Informed consent procedures
  • Adverse event reporting during the investigation

The clinical investigation requirements for AIMDs are more prescriptive than for most general medical devices, reflecting the inherent risk of surgical implantation.

Post-market requirements specific to AIMDs​

AIMDs are subject to the most stringent post-market obligations:

  • Annual PSURs — Periodic Safety Update Reports required at least annually
  • Implant registry participation — UK device registries (e.g., National Joint Registry is Class III orthopaedics; cardiac device registry schemes) may apply
  • Long-duration distribution records — records of the person implanted, the implanting healthcare facility, and the device batch/serial must be maintained for a minimum of 15 years (or the expected device lifetime if longer)
  • Vigilance reporting — all suspected device-related serious incidents must be reported to MHRA within statutory timeframes

Official references​

ReferenceDescription
UK MDR 2002, Part IIFull AIMD provisions
UK MDR 2002, Part II, Schedule 1AIMD Essential Requirements
UK MDR 2002, Part II, Schedule 3AIMD conformity assessment procedures
SI 2019/791Post-Brexit amendments to Part II
MHRA: Active implantable medical devices guidanceMHRA AIMD guidance
EU AIMDD 90/385/EECSource directive for UK Part II (comparative reference)
ISO 14708 seriesImplants for surgery — active implantable devices standards