ICD-10 Code I44.0: Atrioventricular block, first degree

Key Takeaways

ICD-10 Code I44.0 is the billable ICD-10-CM diagnosis code for atrioventricular block, first degree, valid for HIPAA-covered transactions as of October 1, 2025.

First-degree AV block is defined by a PR interval consistently exceeding 200 milliseconds on ECG, without dropped beats.

Documentation must include a confirmed ECG report with PR interval measurement and a physician interpretation note stating clinical significance.

Pabau’s claims management software and structured clinical records help cardiology and internal medicine practices document and submit I44.0 accurately.

ICD-10 Code I44.0 is the billable ICD-10-CM diagnosis code for atrioventricular block, first degree, a conduction delay in which the PR interval on ECG consistently exceeds 200 milliseconds while every impulse still reaches the ventricles. Coders flag this code as a frequent source of denials, usually traced to missing physician interpretation, an undocumented PR interval measurement, or confusion with the second-degree counterpart I44.1. HIPAA-compliant billing workflows require a clean documentation trail before the code reaches a payer. This reference covers the billable status, clinical criteria, documentation requirements, common coding errors, and related codes for ICD-10 Code I44.0.

This guide is written for medical coders, billing staff, cardiologists, and internal medicine clinicians who need a fast, authoritative reference for the ICD-10 Code I44.0 code family.

ICD-10 Code I44.0: Definition and billable status

ICD-10 Code I44.0 is the official ICD-10-CM diagnosis code for atrioventricular block, first degree. According to the Centers for Medicare and Medicaid Services (CMS), it is a billable and specific code valid for use in HIPAA-covered transactions. The 2026 edition of ICD-10-CM I44.0 became effective on October 1, 2025.

The code sits within ICD-10-CM Chapter 9 (Diseases of the Circulatory System), block I30-I5A (Other forms of heart disease), under the I44 parent category for atrioventricular and left bundle-branch block. This placement is important for sequencing: when I44.0 appears on a claim, payers expect documentation consistent with a conduction disorder, not a rhythm disorder such as atrial fibrillation.

I44.0 code details at a glance

Use this quick-reference table before submitting I44.0 on any claim. Every field maps to a payer or CMS data point.

Clinical description: what is first-degree AV block?

First-degree AV block is a cardiac conduction disorder characterized by a consistently prolonged PR interval exceeding 200 milliseconds on a standard ECG or EKG. According to WHO ICD-10 classification and ACC/AHA arrhythmia guidelines, the hallmark of this condition is delayed conduction through the atrioventricular node. Every impulse still reaches the ventricles — no beats are dropped.

That distinction matters for coding. Because no beats are dropped, first-degree AV block is categorically different from second-degree and third-degree block, which involve intermittent or complete failure of impulse conduction. The condition is often benign and may appear as an incidental ECG finding in otherwise healthy patients, though it can carry clinical significance in certain populations, including those on AV-nodal-slowing medications or those with underlying structural heart disease. Coders should never characterize I44.0 as universally benign in documentation.

• PR interval: Consistently greater than 200 ms on a 12-lead ECG
• Conduction: All atrial impulses reach the ventricles (no dropped beats)
• Rhythm: Regular ventricular rhythm — rate unaffected by the block alone
• Presentation: Often asymptomatic; may be discovered during a routine wellness visit ECG
• Clinical significance: Variable — ranges from incidental finding to marker of underlying disease or medication effect

When to use ICD-10 Code I44.0

Apply ICD-10 Code I44.0 when a physician has confirmed first-degree AV block based on ECG findings and documented the diagnosis in the medical record. The code is appropriate in cardiology, internal medicine, and primary care encounters where a prolonged PR interval has been identified and clinically interpreted. It can serve as either a primary diagnosis or a secondary diagnosis alongside the underlying condition driving the conduction delay.

Coders using integrated EHR workflows should look for physician language explicitly naming the degree of block. “AV block” without degree specification is not sufficient to assign I44.0 — an unspecified AV block would point toward I44.30 (left bundle-branch block, unspecified) or other unspecified codes depending on context. The degree must be stated.

• ECG report on file with PR interval measurement documented
• Physician note stating “first-degree AV block” or “first-degree atrioventricular block”
• Encounter in cardiology, internal medicine, or general practice where the finding was evaluated
• Drug therapy monitoring encounters where a medication is suspected of causing the PR prolongation
• Preoperative cardiac evaluations or an annual physical exam checklist that surfaces the finding incidentally

Documentation requirements for atrioventricular block, first degree

Claim denials for I44.0 almost always trace back to incomplete documentation. Payers want to see a coherent clinical record that supports both the code and the visit’s medical necessity. The CDC/NCHS ICD-10-CM guidelines reinforce that physician documentation, not just the ECG tracing itself, drives code assignment.

Practices using digital clinical forms can build structured ECG interpretation templates that prompt physicians to record each of these elements before signing off on the encounter note, alongside a health risk assessment questionnaire capturing broader cardiac risk factors at intake. That structured capture prevents the most common denial trigger: an ECG on file with no accompanying physician narrative.

How I44.0 fits within the I44 heart block ICD-10 code family

The I44 category covers atrioventricular and left bundle-branch block. Understanding where I44.0 sits within this family is essential for choosing the right code — especially because the degrees of AV block carry substantially different clinical weight and, in some cases, different payer requirements.

I44.0 vs I44.1 vs I44.2: choosing the right code

The key differentiator at the point of coding is the ECG interpretation. If the physician documents PR prolongation without dropped beats, I44.0 is correct. If any P wave fails to conduct, the block has progressed beyond first degree. Practices that also bill CPT 00410 for arrhythmia procedures benefit from structured code-selection logic built into their EHR templates.

Drug-induced AV block: coding considerations for I44.0

Several medications commonly used in cardiology and internal medicine can slow AV nodal conduction and produce a first-degree AV block pattern. According to pharmacology references from Purdue CDEK and ACC cardiology guidelines, the primary drug classes associated with drug-induced AV block include beta-blockers, calcium channel blockers, digoxin, and amiodarone.

When a physician documents that first-degree AV block is drug-induced, the encounter documentation should reflect both the conduction finding and the causative agent. Clinicians managing patients who also carry an I10 diagnosis should confirm with their compliance team whether an additional external cause code is warranted under their payer contracts. Coding practice in this area varies by payer and by whether the drug was correctly prescribed versus taken in excess.

• Beta-blockers (metoprolol, atenolol, carvedilol): slow AV nodal conduction directly and are often tracked with a blood pressure log for patients on chronic therapy
• Calcium channel blockers (diltiazem, verapamil): reduce AV node automaticity and conduction velocity
• Digoxin: enhances vagal tone, slowing conduction through the AV node
• Amiodarone: multiple ionic channel effects including AV nodal slowing

Common heart block coding errors to avoid

Coding errors involving the I44 category consistently appear in pre-bill audits. The following mistakes are the most frequently flagged by compliance reviewers and AAPC coding forum discussions.

• Using an unspecified heart block code: Defaulting to an unspecified conduction disorder code when the physician has clearly documented “first degree” is a missed specificity opportunity and may trigger payer edits.
• Omitting ECG documentation: Submitting I44.0 without an ECG report or physician interpretation on file leaves medical necessity unsupported, which payers can deny on audit.
• Upcoding to a higher-degree block: Assigning I44.1 or I44.2 based on the clinician’s concern rather than confirmed ECG findings constitutes upcoding. Code what is documented, not what is suspected.
• Missing physician interpretation: An automated ECG reading or technician report does not satisfy the physician-interpretation requirement. A physician or qualified non-physician practitioner must sign the interpretation.
• Failing to document degree: “AV block” without specifying degree forces the coder toward an unspecified code, which may not be accepted by all payers for certain encounter types.
• Ignoring drug causation: When a medication is documented as the cause, failing to reflect that in the encounter note leaves the claim without context that payers increasingly use for prior authorization and medical necessity reviews.

Practices using structured medical forms embedded in their EHR workflows catch most of these issues before a note is finalized. A checklist at the point of documentation is cheaper than a denial appeal.

Reduce ICD-10 coding errors with structured clinical records

Pabau's claims management tools and digital form builder help cardiology and internal medicine practices document I44.0 accurately, capture ECG findings at the point of care, and submit cleaner claims.

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Related ICD-10 codes to know

The table below covers the codes most frequently used alongside ICD-10 Code I44.0 in cardiology and internal medicine encounters. Coders handling both CPT 93015 stress test billing and cardiac conduction disorders will encounter these regularly. Verified against the AAPC ICD-10-CM code reference.

How Pabau supports accurate ICD-10 coding in cardiology practice

Incomplete documentation is the root cause of most ICD-10 Code I44.0 denials, and the fix is almost always structural rather than behavioral. When cardiologists are prompted by a well-built encounter template, they capture PR interval values, physician interpretation language, and degree specification as a natural part of note completion, not as an afterthought.

Pabau’s claims management software integrates coding documentation with the billing workflow so that cardiology and internal medicine practices can validate required fields before claims leave the system. The structured client record supports custom clinical templates that can include ECG-specific prompts, allowing practices to build the I44.0 documentation checklist directly into their standard encounter note. Standardized templates like these reduce coder rework on cardiac conduction encounters significantly.

Pabau’s AI medical scribe also captures clinician speech during an encounter and structures it into a clinical note, helping to ensure that degree-specific language and PR interval measurements are included without adding documentation time to the visit.

Conclusion

ICD-10 Code I44.0 is a straightforward billable code when the documentation is complete. The most preventable denials come from missing physician interpretation, absent PR interval values, or degree-unspecified notes that force coders toward less specific alternatives. Building structured ECG documentation prompts into your encounter templates eliminates most of these issues at the source.

Pabau’s claims management and structured record tools give cardiology and internal medicine practices the infrastructure to capture every required element at the point of care. To see how it works in practice, book a demo.

Continue your research

Need a reference for other cardiac diagnostic codes? ICD-10 Code I5A covers non-ischemic myocardial injury, another circulatory-system diagnosis coders frequently document alongside conduction disorders.

Need the code for hypertension-related conduction findings? ICD-10 Code I15.1 covers hypertension secondary to renal disorders, a common comorbidity in patients on AV-nodal-slowing medications.

Managing HIPAA-compliant clinical records? HIPAA compliance for medical offices explains the documentation and security requirements that apply to cardiology practices.

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