C1721 — Cardioverter-defibrillator, dual chamber (implantable)
C1721 is a HCPCS Level II code for cardioverter-defibrillator, dual chamber (implantable). It belongs to the Outpatient Prospective Payment System section. Whether Medicare pays it depends on the coverage rule below.
Medicare coverage: Special coverage instructions apply
There are published conditions attached to this code. Check the applicable coverage policy before billing it: the code being valid is not the same as the service being covered.
From the coverage field of the CMS Alpha-Numeric HCPCS File, release 2026Q3-Jul. This states Medicare’s position on the code, not on your particular claim.
Medically Unlikely Edits — units per day
The most units of C1721 Medicare will pay on one date of service. Bill more on a single line and it is denied. The limit is not the same in every setting, so the row that matters is the one matching the claim you are building.
- practitioner
- 1 unit MAI 3 — Date of Service Edit: Clinical · Nature of Equipment
- outpatient
- 1 unit MAI 3 — Date of Service Edit: Clinical · Nature of Equipment
The adjudication indicator decides whether exceeding the limit is worth appealing at all: MAI 1 is a line edit you can support with documentation, MAI 3 is a date-of-service edit that is also appealable, and MAI 2 is absolute — no documentation overrides it. CMS MUE 2026Q3.
The CMS record for C1721
- Long descriptor
- Cardioverter-defibrillator, dual chamber (implantable)
- Short descriptor
- Aicd, dual chamber
- Added
- April 1, 2001
- BETOS
- D1A
- Pricing indicator
- 53 — Other
The official wording. This is what the code means.
CMS's 28-character form, which is what shows up on a remittance advice.
When CMS introduced the code.
Berenson-Eggers Type of Service — CMS's own analytic grouping.
Statute.
Codes adjacent to C1721
HCPCS has no hierarchy — related items simply sit next to each other in the numbering. If C1721 is not quite right, the correct code is very often within a few positions of it.
- C1608Prosthesis, total, dual mobility, first carpometacarpal joint (implantable)
- C1609Vertebral device, motion-preserving, with screw fixation
- C1713Anchor/screw for opposing bone-to-bone or soft tissue-to-bone (implantable)
- C1714Catheter, transluminal atherectomy, directional
- C1715Brachytherapy needle
- C1716Brachytherapy source, non-stranded, gold-198, per source
- C1717Brachytherapy source, non-stranded, high dose rate iridium-192, per source
- C1719Brachytherapy source, non-stranded, non-high dose rate iridium-192, per source
- C1722Cardioverter-defibrillator, single chamber (implantable)
- C1724Catheter, transluminal atherectomy, rotational
- C1725Catheter, transluminal angioplasty, non-laser (may include guidance, infusion/perfusion capability)
- C1726Catheter, balloon dilatation, non-vascular
- C1727Catheter, balloon tissue dissector, non-vascular (insertable)
- C1728Catheter, brachytherapy seed administration
- C1729Catheter, drainage
- C1730Catheter, electrophysiology, diagnostic, other than 3d mapping (19 or fewer electrodes)
Questions about C1721
What is HCPCS code C1721?
C1721 is a HCPCS Level II code for cardioverter-defibrillator, dual chamber (implantable). It sits in the Outpatient Prospective Payment System section.
Does Medicare cover C1721?
The CMS HCPCS file marks C1721 as "Special coverage instructions apply". There are published conditions attached to this code. Check the applicable coverage policy before billing it: the code being valid is not the same as the service being covered.