2027 ICD-10-CM Diagnosis Code I49.01Ventricular fibrillation
ICD-10-CM Codes›I00–I99›I30-I5A›I49
- Billable — Valid for Submission
- MCC — Major Complication or Comorbidity
- Risk Adjusts — HCC 213
- Not Chronic
I49.01 is a billable ICD-10-CM diagnosis code for ventricular fibrillation. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 308 through 310, 791, 793. As a secondary diagnosis, it counts as a major complication or comorbidity (MCC) and places an inpatient stay in the highest severity level of its MS-DRG family. This status applies only when the patient is discharged alive, and not when the principal diagnosis is one of 54 closely related codes. Coders also document this condition as idiopathic cardiac arrest. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Cardiac arrest and ventricular fibrillation.
For Medicare Advantage risk adjustment, I49.01 maps to CMS-HCC Category 213 (Cardio-Respiratory Failure and Shock) under the V28 model, adding a risk factor of about 0.370 for a community, non-dual, aged beneficiary in payment year 2027.
This medical diagnosis code is frequently used in Cardiology medical specialties to designate conditions such cardiac arrhythmias (other).
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
I49.01 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2027.
Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Idiopathic cardiac arrest
- Idiopathic ventricular fibrillation not Brugada type
- Paroxysmal familial ventricular fibrillation
- Sustained ventricular fibrillation
- Ventricular fibrillation
- Ventricular fibrillation and flutter
- Ventricular flutter
- Ventricular tachyarrhythmia
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to I49.01: its own notes plus those printed at I49 and Chapter 9. A note printed at a category, block or chapter applies to every code under it.
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
- certain conditions originating in the perinatal period (P04-P96)
- certain infectious and parasitic diseases (A00-B99)
- complications of pregnancy, childbirth and the puerperium (O00-O9A)
- congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
- endocrine, nutritional and metabolic diseases (E00-E88)
- injury, poisoning and certain other consequences of external causes (S00-T88)
- neoplasms (C00-D49)
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
- systemic connective tissue disorders (M30-M36)
- transient cerebral ischemic attacks and related syndromes (G45.-)
Code First
The underlying condition named in the note is sequenced before this code.
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
ventricular I49.01
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Ventricular Fibrillation
a potentially lethal cardiac arrhythmia that is characterized by uncoordinated extremely rapid firing of electrical impulses (400-600/min) in heart ventricles. such asynchronous ventricular quivering or fibrillation prevents any effective cardiac output and results in unconsciousness (syncope). it is one of the major electrocardiographic patterns seen with cardiac arrest.
Patient EducationClinical
Arrhythmia
An arrhythmia is a problem with the rate or rhythm of your heartbeat. Your heart beats too quickly, too slowly, or with an irregular pattern. Changes in the electrical signals that control your heartbeat cause arrhythmias.
The full article covers:
- What is an arrhythmia?
- What causes an arrhythmia?
- What are the symptoms of an arrhythmia?
- How is an arrhythmia diagnosed?
- What are the treatments for an arrhythmia?
- Can arrhythmias be prevented?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert I49.01 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About I49.01Overview
What is the ICD-10 code for ventricular fibrillation?
The ICD-10-CM code for ventricular fibrillation is I49.01 (sometimes written as I4901). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is I49.01 (Ventricular fibrillation and flutter) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report ventricular fibrillation on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does I49.01 group to?
When ventricular fibrillation is the principal diagnosis on an inpatient stay, it groups to MS-DRG 793, 791, 309, 310, 308, with relative weights from 0.5686 to 4.2192 depending on complications. Higher weights mean higher Medicare reimbursement.
Is I49.01 a CC or MCC?
CMS lists I49.01 as an MCC (major complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it places the inpatient stay in the highest-weighted DRG of its severity family. It carries this status only when the patient is discharged alive. It does not count when the principal diagnosis is one of the 54 closely related codes in its exclusion list.
What is coded first with I49.01?
The Code First note at I49, which applies to I49.01, reads: cardiac arrhythmia complicating: abortion or ectopic or molar pregnancy (O00-O07, O08.8); obstetric surgery and procedures (O75.4). When one of these applies, it is sequenced before I49.01.
What HCC is I49.01?
I49.01 (ventricular fibrillation) maps to CMS-HCC Category 213 (Cardio-Respiratory Failure and Shock), commonly written as HCC 213, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 84 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. It does not map to any RxHCC in the Part D prescription drug model.
Does I49.01 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, I49.01 adds a risk adjustment factor of about 0.370 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.258 to 0.662 depending on the payment segment). A more severe related category (HCC 211 and HCC 212) supersedes it when both are reported. See the full factor table on the HCC 213 category page.
