Thrombolysis coding trips up even experienced coders because, unlike most procedures, it isn’t billed once — it’s billed per calendar day, sometimes across multiple days of treatment. This guide walks through exactly how catheter-directed thrombolysis is coded, with real-world examples so you can apply the rules with confidence.
What Is Catheter-Directed Thrombolysis?
Catheter-directed thrombolysis is a procedure in which a physician guides a catheter directly into an artery or vein to deliver a clot-dissolving medication — most commonly tissue plasminogen activator (tPA) — right at the site of the blockage. The lytic agent is infused gradually, often over an extended period.
This procedure can be:
- Performed on its own as a stand-alone treatment
- Performed before or after other vascular procedures
Because clots don’t always dissolve quickly, it’s common for thrombolysis to continue for two or more days. That’s exactly why CPT created a set of codes built around treatment days rather than a single procedure code.
Key Coding Rules You Need to Know First
Before getting into the specific codes, here are the foundational rules that govern nearly every thrombolysis claim:
- Codes 37211 and 37212 do not include catheterization, diagnostic angiography, or other interventions. These must be coded separately when performed and documented.
- Ultrasound guidance for vascular access (76937) can be coded separately when it meets the documentation requirements in the code description.
- E/M visits related to thrombolysis on the same day are bundled in — they are not separately billable.
- Codes are assigned once per calendar day, and that single code covers all imaging and catheter repositioning/exchanges performed that day — no matter how many times the patient returns to the treatment room.
- Do not report 75898 (angiography during follow-up) for follow-up angiograms performed during a thrombolytic infusion — it’s already included.
- Thrombolysis codes are unilateral. For bilateral thrombolysis through separate accesses, append modifier 50. For thrombolysis in two entirely separate vascular beds (for example, a renal artery and a femoral artery), append modifier 59 instead.
- These codes are meant for prolonged infusions only. Per AMA guidance given at the CPT Symposium, the patient must leave the treatment room with the infusion still running for these codes to apply.
- Do not use a thrombolysis infusion code for a thrombolytic agent injected during a mechanical thrombectomy procedure.
- Not for intracranial thrombolysis. If the thrombolysis is inside the brain, use code 61645 instead — not 37211–37214.
The Core Thrombolysis Codes
37211 — Arterial Thrombolysis, Initial Treatment Day
Transcatheter therapy, arterial infusion for thrombolysis other than coronary or intracranial, any method, including radiological supervision and interpretation, initial treatment day
Use 37211 to report the first day of arterial thrombolysis. This single code covers the initial infusion plus any follow-up evaluation, imaging, or catheter repositioning/exchange performed that same day.
37212 — Venous Thrombolysis, Initial Treatment Day
Transcatheter therapy, venous infusion for thrombolysis, any method, including radiological supervision and interpretation, initial treatment day
Same concept as 37211, but for venous thrombolysis instead of arterial.
If thrombolysis starts and ends on the same calendar day, only the initial treatment day code (37211 or 37212) is reported — no additional codes are needed.
37213 — Continued Thrombolysis, Subsequent Day (Middle Days)
Transcatheter therapy, arterial or venous infusion for thrombolysis… continued treatment on subsequent day…
When thrombolysis lasts three or more days, use 37213 for every day except the first day and the last day. It applies to either arterial or venous thrombolysis and covers all related work performed that calendar day, including follow-up catheter contrast injections, position changes, or catheter exchanges.
37214 — Cessation of Thrombolysis (Final Day)
Transcatheter therapy, arterial or venous infusion for thrombolysis… cessation of thrombolysis including removal of catheter and vessel closure by any method
Use 37214 for the final day of thrombolysis treatment. Like the other codes in this family, it’s assigned per calendar day and bundles in any follow-up exams or catheter work performed that day. It also includes catheter removal and closure of the access site — so don’t code those separately.
Worked Examples: How the Codes Come Together
Example 1: A Two-Day Thrombolysis Procedure
Day 1, 1:00 p.m. — The left common femoral artery is catheterized via a right groin access, and a diagnostic left lower extremity angiogram is performed. Thrombolysis is initiated in the left popliteal artery.
Day 1, 5:00 p.m. — Follow-up angiogram performed; thrombolysis resumed.
Day 2, 8:00 a.m. — Follow-up angiogram performed. Mechanical thrombectomy is performed in the popliteal artery; the thrombolysis catheter is removed, suction thrombectomy performed, and a new thrombolysis catheter placed. Thrombolysis resumes.
Day 2, 4:00 p.m. — Follow-up angiogram performed. Thrombolysis is stopped, the catheter removed, and a closure device deployed.
Codes assigned:
- Day 1: 36247, 75710-59, 37211
- Day 2: 37214, 37186
Example 2: A Three-Day Thrombolysis Procedure
Day 1, 1:00 p.m. — Left common femoral artery catheterized via right groin access; diagnostic angiogram performed. Thrombolysis initiated in the left popliteal artery.
Day 1, 5:00 p.m. — Follow-up angiogram; thrombolysis resumed.
Day 2, 8:00 a.m. — Follow-up angiogram. Mechanical thrombectomy performed; thrombolysis catheter removed, suction thrombectomy performed, new catheter placed. Thrombolysis resumed.
Day 2, 4:00 p.m. — Follow-up angiogram; thrombolysis resumed.
Day 3, 8:00 a.m. — Follow-up angiogram; thrombolysis resumed.
Day 3, 12:00 p.m. — Follow-up angiogram; catheter repositioned; thrombolysis resumed.
Day 3, 4:00 p.m. — Follow-up angiogram. Thrombolysis discontinued, catheter removed, closure device deployed.
Codes assigned:
- Day 1: 36247, 75710-59, 37211
- Day 2: 37213, 37186
- Day 3: 37214
Coding Separate Vascular Beds or Extremities
Because thrombolysis codes are unilateral, things get more complex when thrombolysis is started in more than one leg or vascular bed — especially if one side stops before the other. In these situations, each procedure is coded separately.
Example 1: Arterial Thrombolysis in Both Legs
Arterial thrombolysis begins Monday in both legs. It’s discontinued Tuesday in the left leg but continues through Wednesday in the right leg.
Codes assigned:
- Monday: 37211-50
- Tuesday: 37214-LT, 37213-RT
- Wednesday: 37214-RT
Example 2: Venous Thrombolysis Started at Different Times
Venous thrombolysis begins Monday in the right leg and is discontinued Tuesday. Thrombolysis then begins in the left leg and is discontinued Wednesday.
Codes assigned:
- Monday: 37212-RT
- Tuesday: 37214-RT, 37212-LT
- Wednesday: 37214-LT
Medicare NCCI Edits and MUE Limits to Know
Coders working with Medicare claims need to be aware of these specific edits:
- NCCI edits prevent billing 37211 or 37212 together with 37213 or 37214, and also prevent billing 37213 and 37214 together.
- Bilateral billing with modifier 50 is allowed and reimburses at 150% of the Medicare Physician Fee Schedule, assuming medical necessity is documented.
- All four codes (37211–37214) have an MUE (Medically Unlikely Edit) of 1 per day, with an MUE Adjudication Indicator (MAI) of 2. In practice, this means:
- Medicare will not pay for the same code twice in one day unless it’s billed on a single line with modifier 50.
- If billed with modifier 59 or with RT/LT modifiers instead of modifier 50, all line items with those codes will be denied.
- A Medicare contractor generally cannot override the MUE, except when following a post-appeal directive from a Qualified Independent Contractor (QIC) or Administrative Law Judge (ALJ).
Cerebral Thrombolysis: A Different Set of Codes
Codes 37211–37214 are specifically for thrombolysis outside the brain. Cerebral (intracranial) thrombolysis uses its own codes entirely.
37195 — Cerebral Thrombolysis by IV Infusion
Thrombolysis, cerebral, by intravenous infusion
This code is used for initiating an IV infusion to treat acute ischemic stroke, typically started in the emergency department. If a separately documented E/M service is also provided, it may be coded in addition.
61645 — Intracranial Mechanical Thrombectomy and/or Thrombolysis Infusion
Percutaneous arterial transluminal mechanical thrombectomy and/or infusion for thrombolysis, intracranial, any method, including diagnostic angiography, fluoroscopic guidance, catheter placement, and intraprocedural pharmacological thrombolytic injection(s)
Code 61645 reports cerebral mechanical thrombectomy and/or thrombolysis infusion, including revascularization using mechanical thrombectomy devices, aspiration thrombectomy catheters, and administration of thrombolytics or IIb/IIIa inhibitors (such as ReoPro®, Integrilin®, or Aggrastat®).
Three intracranial vascular territories are defined by CPT for reporting 61645 (as well as 61650/61651):
- Right carotid circulation
- Left carotid circulation
- Vertebro-basilar circulation
Report 61645 only once per territory, regardless of how many arteries within that territory were treated.
Code 61645 is a complete, all-inclusive code. It bundles in:
- Vascular catheterization
- Diagnostic angiography
- Imaging supervision and interpretation
- Follow-up imaging
- Fluoroscopic guidance
- Neurologic and hemodynamic monitoring
- Closure of the arteriotomy
- The thrombectomy/thrombolysis procedure itself
Do not report CPT codes 36221–36228, 37184, 61630, 61635, 61650, or 61651 in addition to 61645 for the same vascular territory.
Quick-Reference Summary Table
| Situation | Code |
|---|---|
| Arterial thrombolysis, Day 1 (initial) | 37211 |
| Venous thrombolysis, Day 1 (initial) | 37212 |
| Thrombolysis continues, middle treatment days | 37213 |
| Final day — thrombolysis stopped, catheter removed | 37214 |
| Bilateral thrombolysis, same day, separate accesses | Add modifier 50 |
| Thrombolysis in two separate vascular beds | Add modifier 59 |
| Cerebral thrombolysis via IV infusion | 37195 |
| Intracranial mechanical thrombectomy/thrombolysis | 61645 |
Frequently Asked Questions
Can I bill a thrombolysis code more than once on the same day? No. Codes 37211–37214 are assigned once per calendar day and cover all imaging and catheter work performed that day, no matter how many times the patient returns to the treatment room.
What if thrombolysis starts and stops on the same day? Only the initial treatment day code (37211 or 37212) is reported — no additional codes are needed for that day.
Do I need to code catheterization separately for thrombolysis? Yes, in most cases. Codes 37211 and 37212 do not include catheterization, diagnostic angiography, or other interventions — those should be coded separately when documented.
Are thrombolysis codes billed per side (unilateral) or do they cover both sides automatically? They’re unilateral. Bilateral thrombolysis through separate accesses requires modifier 50; thrombolysis in two separate vascular beds requires modifier 59.
Which code should I use for thrombolysis inside the brain? Use 37195 for cerebral thrombolysis by IV infusion, or 61645 for intracranial mechanical thrombectomy and/or thrombolysis infusion — never 37211–37214.
