I21.B: Myocardial infarction with coronary microvascular dysfunction

I21.B, myocardial infarction with coronary microvascular dysfunction, is listed as a covered diagnosis in 8 Medicare billing and coding articles that apply to 49 HCPCS Level II codes, including G0422 (Intensive cardiac rehabilitation; with or without…), G0423 (Intensive cardiac rehabilitation; with or without…), J0153 (Injection, adenosine, 1 mg (not to be used to report any…). 5 of these codes have a 2026 DMEPOS fee schedule amount; K0606 pays $3,588.90 (RR) depending on the state. The articles come from 4 Medicare contractors. A listed diagnosis supports medical necessity only; coverage still depends on the LCD's criteria and on documentation in the medical record.

HCPCS Level II codes with I21.B as a covered diagnosis

CodeDescriptionMedicare coverageDMEPOS fee 2026 (state range)Articles listing it
G0422Intensive cardiac rehabilitation; with or without continuous ecg monitoring with exercise, per sessionCarrier judgment—1
G0423Intensive cardiac rehabilitation; with or without continuous ecg monitoring; without exercise, per sessionCarrier judgment—1
J0153Injection, adenosine, 1 mg (not to be used to report any adenosine phosphate compounds)Special coverage instructions apply—4
J1250Injection, dobutamine hydrochloride, per 250 mgSpecial coverage instructions apply—4
J1245Injection, dipyridamole, per 10 mgSpecial coverage instructions apply—4
K0606Automatic external defibrillator, with integrated electrocardiogram analysis, garment typeCarrier judgment$3,588.90 (RR)1
K0609Replacement electrodes for use with automated external defibrillator, garment type only, eachCarrier judgment$1,148.78–$1,378.591
E0617External defibrillator with integrated electrocardiogram analysisCarrier judgment$433.30–$577.30 (RR)1
K0608Replacement garment for use with automated external defibrillator, eachCarrier judgment$172.74–$230.11 (NU)1
K0607Replacement battery for automated external defibrillator, garment type only, eachCarrier judgment$27.69–$36.87 (RR)1
A9999Miscellaneous dme supply or accessory, not otherwise specifiedCarrier judgment—1
A9500Technetium tc-99m sestamibi, diagnostic, per study doseCarrier judgment—2
A9502Technetium tc-99m tetrofosmin, diagnostic, per study doseCarrier judgment—2
A9505Thallium tl-201 thallous chloride, diagnostic, per millicurieCarrier judgment—2
A9501Technetium tc-99m teboroxime, diagnostic, per study doseCarrier judgment—2
C9600Percutaneous transcatheter placement of drug eluting intracoronary stent(s), with coronary angioplasty when performed; single major coronary artery or branchSpecial coverage instructions apply—1
C9601Percutaneous transcatheter placement of drug-eluting intracoronary stent(s), with coronary angioplasty when performed; each additional branch of a major coronary artery (list separately in addition to code for primary procedure)Special coverage instructions apply—1
C9602Percutaneous transluminal coronary atherectomy, with drug eluting intracoronary stent, with coronary angioplasty when performed; single major coronary artery or branchSpecial coverage instructions apply—1
C9603Percutaneous transluminal coronary atherectomy, with drug-eluting intracoronary stent, with coronary angioplasty when performed; each additional branch of a major coronary artery (list separately in addition to code for primary procedure)Special coverage instructions apply—1
C9604Percutaneous transluminal revascularization of or through coronary artery bypass graft (internal mammary, free arterial, venous), any combination of drug-eluting intracoronary stent, atherectomy and angioplasty, including distal protection when performed; single vesselSpecial coverage instructions apply—1
C9605Percutaneous transluminal revascularization of or through coronary artery bypass graft (internal mammary, free arterial, venous), any combination of drug-eluting intracoronary stent, atherectomy and angioplasty, including distal protection when performed; each additional branch subtended by the bypass graft (list separately in addition to code for primary procedure)Special coverage instructions apply—1
C9606Percutaneous transluminal revascularization of acute total/subtotal occlusion during acute myocardial infarction, coronary artery or coronary artery bypass graft, any combination of drug-eluting intracoronary stent, atherectomy and angioplasty, including aspiration thrombectomy when performed, single vesselSpecial coverage instructions apply—1
C9607Percutaneous transluminal revascularization of chronic total occlusion, coronary artery, coronary artery branch, or coronary artery bypass graft, any combination of drug-eluting intracoronary stent, atherectomy and angioplasty; single vesselSpecial coverage instructions apply—1
C9608Percutaneous transluminal revascularization of chronic total occlusion, coronary artery, coronary artery branch, or coronary artery bypass graft, any combination of drug-eluting intracoronary stent, atherectomy and angioplasty; each additional coronary artery, coronary artery branch, or bypass graft (list separately in addition to code for primary procedure)Special coverage instructions apply—1
J0461Injection, atropine sulfate, 0.01 mgSpecial coverage instructions apply—3

24 more codes are listed. See every code with payment by region in Caduvo.

Medicare policy articles listing I21.B

A diagnosis listed as covered in a billing and coding article supports medical necessity for the article's codes; it does not guarantee payment. Coverage depends on the LCD's criteria, the contractor's jurisdiction and documentation in the medical record.

Other I21 diagnoses (Acute myocardial infarction)

Frequently asked questions

Does Medicare cover I21.B (Myocardial infarction with coronary microvascular…)?

Medicare covers items and services, not diagnoses. 8 Medicare billing and coding articles list I21.B as a covered diagnosis for 49 HCPCS Level II codes: the diagnosis can support medical necessity for those codes, but payment still depends on the LCD's coverage criteria and the medical record.

Which HCPCS codes can be billed with ICD-10 I21.B?

The Level II codes from the policies most specific to this diagnosis are G0422 (Intensive cardiac rehabilitation; with or without…, 1 article); G0423 (Intensive cardiac rehabilitation; with or without…, 1 article); J0153 (Injection, adenosine, 1 mg (not to be used to report any…, 4 articles); J1250 (Injection, dobutamine hydrochloride, per 250 mg, 4 articles); J1245 (Injection, dipyridamole, per 10 mg, 4 articles). Code choice depends on the item supplied; check each code's descriptor.

What does Medicare pay for equipment billed with I21.B?

Under the 2026 DMEPOS fee schedule (non-rural state fees): K0606 $3,588.90 (RR); K0609 $1,148.78 to $1,378.59; E0617 $433.30 to $577.30 (RR); K0608 $172.74 to $230.11 (NU). Medicare pays 80% of the allowed amount after the Part B deductible.

Which Medicare policy articles list I21.B?

A53775 (Billing and Coding: Frequency and Duration for Cardiac Rehabilitation and Intensive Cardiac Rehabilitation); A52458 (Automatic External Defibrillators - Policy Article); A56823 (Billing and Coding: Percutaneous Coronary Intervention), and 5 more articles.

What is ICD-10-CM code I21.B?

I21.B is the ICD-10-CM code for myocardial infarction with coronary microvascular dysfunction, in category I21 (Acute myocardial infarction), chapter 9: Diseases of the circulatory system.

Next steps

Sources: CMS Medicare Coverage Database billing and coding articles (covered ICD-10 code lists and HCPCS links); ICD-10-CM FY2026; CMS HCPCS Level II release October 2026; CMS DMEPOS fee schedule 2026 (non-rural state fees). Not billing or legal advice.

Chapter 9: Diseases of the circulatory system · All diagnoses · HCPCS lookup