Chapter 9 — Diseases of the Circulatory System
Hypertension and the “with” presumption, the I11 / I12 / I13 decision, myocardial infarction by type, and the I69 sequelae rules.
Chapter 9 is built on one convention and one clinical distinction. The convention is “with”: hypertension is presumed causally related to heart involvement and to kidney involvement, so I11, I12 and I13 are assigned without any linking statement from the provider. The distinction is myocardial infarction type — type 1 codes to I21.0–I21.4, type 2 to I21.A1, and types 3, 4 and 5 to I21.A9.
Hypertension — the twelve rules#
The classification presumes a causal relationship between hypertension and heart involvement, and between hypertension and kidney involvement, because the two are linked by the term “with” in the Alphabetic Index. They are coded as related even in the absence of provider documentation explicitly linking them, unless the documentation clearly states the conditions are unrelated. For hypertension and conditions not linked by relational terms, provider documentation must link them.
| # | Rule | Codes |
|---|---|---|
| 1 | Hypertension with heart disease — one or more conditions classified to I50.-, I51.4, I51.89 or I51.9 | 1a code from I112an additional code from I50 or I51 to identify the heart condition |
| 1 | Hypertension with I51.5 myocardial degeneration or I51.7 cardiomegaly | A code from I11 only — no additional code for the specific heart condition |
| 1 | The same heart conditions documented by the provider as unrelated to the hypertension | Code separately: I10 or a code from I15, plus the heart condition. Sequence by the circumstances of the encounter |
| 2 | Hypertensive chronic kidney disease — hypertension and a condition classifiable to N18 | 1a code from I122a code from N18 to identify the CKD stage |
| 2 | Provider indicates the CKD is not related to the hypertension | NEVER CKD is not coded as hypertensive |
| 2 | Hypertensive CKD and acute renal failure | Code the acute renal failure as well. Sequence by the circumstances of the encounter |
| 3 | Hypertensive heart and chronic kidney disease — hypertension with both heart and kidney disease | 1a code from I132an additional code from I50 if heart failure is present3a code from N18 to identify the CKD stage |
| 3 | The Includes note at I13 | The conditions included at I11 and I12 are included together in I13. Where a patient has hypertension, heart disease and CKD, use I13 — NEVER not I11 or I12 |
| 4 | Hypertensive cerebrovascular disease | 1the appropriate code from I60–I692the appropriate hypertension code |
| 5 | Hypertensive retinopathy | H35.0- with a code from I10–I15. Sequencing is based on the reason for the encounter |
| 6 | Secondary hypertension — due to an underlying condition | Two codes: the underlying etiology, and a code from I15. Sequencing is determined by the reason for the encounter |
| 7 | Transient hypertension | R03.0 elevated blood pressure reading without diagnosis of hypertension, unless the patient has an established diagnosis of hypertension. In pregnancy, O13.- or O14.- |
| 8 | Controlled hypertension | The appropriate code from I10–I15 |
| 9 | Uncontrolled hypertension — untreated, or not responding to therapy | The appropriate code from I10–I15. There is no separate code for uncontrolled hypertension |
| 10 | Hypertensive crisis — urgency, emergency or unspecified crisis | A code from I16, and code also any identified hypertensive disease I10–I15, I1A. Sequencing is based on the reason for the encounter |
| 11 | Pulmonary hypertension — category I27 | For secondary pulmonary hypertension I27.1, I27.2-, code also any associated conditions or adverse effects of drugs or toxins. Sequencing by the reason for the encounter, except for adverse effects of drugs |
| 12 | Resistant hypertension — apparent treatment resistant, treatment resistant or true resistant hypertension documented by the provider | I1A.0 as an additional code, with a code for the specific type of existing hypertension sequenced first, if known |
Coronary artery disease and angina#
| Point | Rule |
|---|---|
| Combination codes | I25.11- atherosclerotic heart disease of native coronary artery with angina pectoris, and I25.7- atherosclerosis of coronary artery bypass graft(s) and coronary artery of transplanted heart with angina pectoris |
| Additional angina code | NEVER Not necessary when using one of these combination codes |
| Causal relationship | A causal relationship can be assumed in a patient with both atherosclerosis and angina pectoris, unless the documentation indicates the angina is due to something other than the atherosclerosis |
| CAD patient admitted with an acute MI | The AMI is sequenced before the coronary artery disease |
Acute myocardial infarction — type decides the code#
| Type or situation | Code | Notes |
|---|---|---|
| Type 1 STEMI | I21.0-–I21.2-, I21.3 | Codes identify the site, such as anterolateral wall or true posterior wall |
| Type 1 NSTEMI | I21.4 | Also used for nontransmural MIs |
| Type 1 NSTEMI that evolves to STEMI | Assign the STEMI code | — |
| Type 1 STEMI that converts to NSTEMI due to thrombolytic therapy | It is still coded as STEMI | — |
| Unspecified AMI, or unspecified type | I21.9 | The default |
| Type 1 STEMI or transmural MI documented without the site | I21.3 | ST elevation myocardial infarction of unspecified site |
| AMI documented as nontransmural or subendocardial but the site is provided | Still coded as a subendocardial AMI | The site does not convert it to a transmural MI |
| Type 2 MI — due to demand ischemia or secondary to ischemic imbalance | I21.A1 | Code the underlying cause first, if applicable. NEVER Do not assign I24.89 for the demand ischemia. If a type 2 AMI is described as NSTEMI or STEMI, assign only I21.A1 |
| Types 3, 4a, 4b, 4c and 5 | I21.A9 | Follow the “Code also” and “Code first” notes for complications and for postprocedural MIs during or following cardiac surgery |
| MI with coronary microvascular dysfunction | I21.B | Also for MI with coronary microvascular disease and MINOCA with microvascular disease |
Timing and subsequent infarction
| Situation | Assign |
|---|---|
| Encounters occurring while the MI is equal to or less than four weeks old, including transfers to another acute or post-acute setting, where the MI meets the definition for other diagnoses | Codes from category I21 may continue to be reported |
| Encounters after the four-week time frame, patient still receiving care related to the MI | The appropriate aftercare code, rather than a code from I21 |
| Old or healed MI not requiring further care | I25.2 |
| A patient who has suffered a type 1 or unspecified AMI has a new AMI within the four-week time frame | A code from I22, which must be used with a code from I21. Sequencing depends on the circumstances of the encounter |
| Subsequent type 2 AMI | NEVER Do not assign I22. Assign only I21.A1 |
| Subsequent type 4 or type 5 AMI | NEVER Do not assign I22. Assign only I21.A9 |
| A subsequent MI of one type occurring within four weeks of an MI of a different type | Assign the appropriate codes from I21 to identify each type. NEVER Do not assign a code from I22. I22 is only for cases where both the initial and the subsequent MI are type 1 or unspecified |
Cerebrovascular accident and its sequelae#
| Situation | Rule |
|---|---|
| Intraoperative and postprocedural CVA | Medical record documentation must clearly specify the cause-and-effect relationship between the medical intervention and the cerebrovascular accident. Code assignment then depends on whether it was an infarction or a hemorrhage, and on whether it occurred intraoperatively or postoperatively. For a cerebral hemorrhage, code assignment depends on the type of procedure performed |
Category I69 sequelae | Used to indicate conditions classifiable to I60–I67 as the causes of sequela — neurologic deficits — classified elsewhere. These late effects include neurologic deficits that persist after initial onset, and may be present from the onset or arise at any time afterwards |
Dominant / nondominant in I69 | Codes specifying hemiplegia, hemiparesis and monoplegia identify dominant or nondominant side. Defaults where the side is documented but dominance is not: ambidextrous → dominant; left → non-dominant; right → dominant |
I69 together with I60–I67 | ALWAYS Permitted on the same record, where the patient has a current cerebrovascular disease and deficits from an old cerebrovascular disease |
I69 where there are no neurologic deficits | NEVER Codes from I69 should not be assigned. Use the personal history code Z86.73 — see Section I.C.21.c.4 |
Practice questions#
Q1A patient has essential hypertension, systolic heart failure and stage 4 chronic kidney disease. The provider has not written any statement linking the conditions. What is assigned?
- A
I10,I50.2-,N18.4 - B
I11.0andI12.9, plusI50.2-andN18.4 - CA code from
I13, plus a code fromI50for the type of heart failure, plusN18.4 - D
I13.0alone
Show answer & rationale
Correct answer: C. A code from I13, plus a code from I50 for the type of heart failure, plus N18.4
Rationale. Guideline I.C.9.a.3 states that the codes in category I13 are combination codes that include hypertension, heart disease and chronic kidney disease, that an additional code from I50 is assigned if heart failure is present, and that a code from N18 is used as a secondary code to identify the stage. The Includes note at I13 means that where a patient has all three, I13 is used rather than I11 or I12. No linking statement is required, because the classification presumes the causal relationship.
Q2A patient is admitted with a type 2 myocardial infarction described in the record as an NSTEMI, due to demand ischemia from severe anaemia. What is assigned for the MI?
- A
I21.4andI24.89 - B
I21.A1only, with the underlying cause coded first - C
I21.4only - D
I21.A1andI21.4
Show answer & rationale
Correct answer: B. I21.A1 only, with the underlying cause coded first
Rationale. Guideline I.C.9.e.5 states that type 2 myocardial infarction is assigned to I21.A1 with the underlying cause coded first if applicable, that I24.89 should not be assigned for the demand ischemia, that if a type 2 AMI is described as NSTEMI or STEMI only I21.A1 is assigned, and that codes I21.01-I21.4 should only be assigned for type 1 AMIs.
Q3A patient sustained a type 1 STEMI three weeks ago and now has a new type 1 NSTEMI. What is assigned?
- A
I21.4only - BA code from
I22used together with a code fromI21 - C
I22only - DTwo codes from
I21
Show answer & rationale
Correct answer: B. A code from I22 used together with a code from I21
Rationale. Guideline I.C.9.e.4 states that a code from category I22 is used when a patient who has suffered a type 1 or unspecified AMI has a new AMI within the four-week time frame of the initial AMI, that a code from I22 must be used in conjunction with a code from I21, and that the sequencing depends on the circumstances of the encounter. Because both infarctions are type 1, I22 applies.
Q4A patient has hemiplegia affecting the left side following a cerebral infarction two years ago. The record does not state whether the left side is dominant. What default applies?
- ADominant
- BNon-dominant
- CUnspecified
- DQuery is required
Show answer & rationale
Correct answer: B. Non-dominant
Rationale. Guideline I.C.9.d.1 sets the defaults for I69 codes specifying hemiplegia, hemiparesis and monoplegia where the affected side is documented but not specified as dominant or nondominant: for ambidextrous patients the default is dominant, if the left side is affected the default is non-dominant, and if the right side is affected the default is dominant. The identical defaults appear at I.C.6.a for category G81.
Q5A patient with atherosclerotic heart disease of a native coronary artery and stable angina pectoris is seen in the office. Nothing in the record attributes the angina to another cause. What is assigned?
- A
I25.10and a separate angina code - BA combination code from
I25.11- - CThe angina code only
- D
I25.10only
Show answer & rationale
Correct answer: B. A combination code from I25.11-
Rationale. Guideline I.C.9.b states that ICD-10-CM has combination codes for atherosclerotic heart disease with angina pectoris in subcategories I25.11 and I25.7, that when using one of these combination codes it is not necessary to use an additional code for angina pectoris, and that a causal relationship can be assumed in a patient with both atherosclerosis and angina pectoris unless the documentation indicates the angina is due to something other than the atherosclerosis.
Scenarios#
A cardiology note documents essential hypertension and chronic diastolic heart failure, and states explicitly: “the heart failure is secondary to severe aortic stenosis and is not hypertensive in origin.”
Show coded answer & rationale
| Seq | Code | Description |
|---|---|---|
| 1 | I10 | Essential (primary) hypertension |
| 2 | I50.32 | Chronic diastolic (congestive) heart failure |
| 3 | I35.0 | Nonrheumatic aortic (valve) stenosis |
Rationale. Guideline I.C.9.a.1 provides that the same heart conditions with hypertension are coded separately if the provider has documented they are unrelated to the hypertension, in which case I10 or a code from I15 is assigned and sequencing follows the circumstances of the encounter. This is one of the two circumstances in which the “with” presumption of Section I.A.15 is defeated — documentation that clearly states the conditions are unrelated.
Guideline: Section I.A.15, I.C.9.a.1
A patient with residual right-sided hemiparesis from a cerebral infarction four years ago is admitted with a new acute cerebral infarction. Dominance is not documented.
Show coded answer & rationale
| Seq | Code | Description |
|---|---|---|
| 1 | I63.9 | Cerebral infarction, unspecified — or the specific code the record supports; principal diagnosis |
| 2 | I69.351 | Hemiplegia and hemiparesis following cerebral infarction affecting right dominant side — verify in the Tabular List |
| 3 | R29.7- | NIHSS score, if documented, sequenced after the acute stroke code |
Rationale. Guideline I.C.9.d.2 states that codes from category I69 may be assigned on a health care record with codes from I60-I67 if the patient has a current cerebrovascular disease and deficits from an old cerebrovascular disease. Guideline I.C.9.d.1 supplies the dominance default: right side affected, dominance not documented, defaults to dominant. Section I.C.18.i directs that NIHSS codes may be used with acute stroke codes I60-I63 and are sequenced after the acute stroke diagnosis codes.
Guideline: Section I.C.9.d.1, I.C.9.d.2, I.C.18.i
A patient with known essential hypertension, documented by the provider as “true resistant hypertension” on four antihypertensive agents, presents with a hypertensive emergency.
Show coded answer & rationale
| Seq | Code | Description |
|---|---|---|
| 1 | I16.1 | Hypertensive emergency |
| 2 | I10 | Essential (primary) hypertension |
| 3 | I1A.0 | Resistant hypertension |
Rationale. Guideline I.C.9.a.10 directs assignment of a code from category I16 for a documented hypertensive urgency, hypertensive emergency or unspecified hypertensive crisis, with a “code also” instruction for any identified hypertensive disease I10-I15, I1A, and states that sequencing is based on the reason for the encounter. Guideline I.C.9.a.12 directs I1A.0 as an additional code when apparent treatment resistant, treatment resistant or true resistant hypertension is documented by the provider, with the specific type of existing hypertension sequenced first if known.
Guideline: Section I.C.9.a.10, I.C.9.a.12
Primary sources#
- ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027CMS — the source document for every page on this site (effective 1 Oct 2026)
- NCHS ICD-10-CM files — Tabular List, Index, POA exempt listOfficial code files, addenda and the list of codes exempt from POA reporting
- ICD-10 Coordination and Maintenance CommitteeWhere code proposals are debated; agendas, summaries and meeting materials
- CMS ICD-10 homeCode sets, transition guidance and Medicare coding policy
- AHA Coding ClinicOfficial coding advice from the AHA Central Office — subscription required
- HHS OIG Work PlanActive audit topics — useful for prioritising internal coding audits
- MEDESUN Medical Coding AcademyTraining, credential preparation and audit services by the author