Cardiomyopathy: Understand the intent behind the codes

by Robert S. Gold, MD

The goals of coding should always be ensuring data accuracy and capturing a patient’s true clinical picture.

Knowing the intent of an ICD-9-CM code is crucial. However, coding guidelines and official coding guidance sometimes conflict with these goals, putting coders and CDI specialists between a rock and a hard place.

Cardiomyopathy (CMP), a disease that affects the heart muscle, is an example of a diagnosis that is frequently misreported due to inaccurate guidance.

First and foremost, coders and CDI specialists must understand that when cardiologists document the term “CMP,” it usually denotes their awareness that the patient has a sick heart. The physician may evaluate the heart as being dilated and as having a low ejection fraction. However, they don’t always evaluate pathophysiology. Without this evaluation, documentation of CMP can be deceiving. When coders see this documentation, they report ICD-9-CM code 425.4 for the CMP even when the patient may have something else.

Causes of CMP

A quick Google search yields a variety of causes of CMP. There are specific ICD-9-CM codes in the 425 code series for each type of CMP. For example, codes 425.11 and 425.18 denote idiopathic hypertrophic CMP with or without obstruction, respectively.

Code 425.5 denotes alcoholic CMP. Code 425.7 denotes nutritional CMPs, such as due to amyloidosis and beriberi. Some very rare CMPs are also specifically named in this section. Two examples are endocardial fibroelastosis (code 425.3) and obscure CMP of Africa (code 425.2).

Code 425.8 denotes other specified CMPs in diseases classified elsewhere that can also affect the heart muscle and its function. These include Friedreich’s ataxia, progressive muscular dystrophy, sarcoidosis, and myotonia atrophica.

Other specific causes of CMP are not included in the 425 code series.

If you look for hypertensive CMP in the Alphabetic Index of the ICD-9-CM Manual, it leads you to hypertension with cardiac involvement. This leads you to the 402–404 code series. Hypertensive CMP is a type of CMP; however, it doesn’t exist in the 425 code series. Coding Clinic, 2nd Quarter 1993, p. 9, instructs coders to assign both the 402 (or 404) series code and code 425.8 to designate CMP in diseases that are classified elsewhere.

Similarly, ischemic CMP (code 414.8) is not listed under CMP even though it is a cause of heart disease that can lead to dysfunction. No advice exists for the addition of code 425.8 even though it is among the most frequent causes of CMP in the United States. This represents an error in the coding system. ICD-9-CM code 414.8 denotes ischemic heart disease just as codes 403 and 404 denote hypertensive heart disease. They each require code 425.8 to capture the complete description of the condition.

Several Coding Clinic references cite code 425.4 (other primary CMPs) for CMP. These references state that coders should report this code for CMP that includes such terms as “congestive,” “constrictive,” “familial,” “idiopathic,” “restrictive,” or “obstructive.” However, these references are incorrect. Code 425.4 should be used only for primary CMPs not otherwise specified or when physicians document one of the aforementioned nonessential modifiers.

When a patient has CMP that is secondary to another condition (and the cause is unknown) coders should report code 425.9 (secondary CMP, unspecified).

When the cause is known, they should report code 425.8. These codes (i.e., 425.8 and 425.9) should be used when documentation includes any one of the nonessential modifiers listed under code 425.4 and when the CMP is due to another condition.

The term “idiopathic” means that the physician cannot determine the cause of the CMP despite extensive workup. If the physician can determine the cause, then by definition it’s secondary CMP.

Ischemic heart disease is a disease classified elsewhere. Similarly, hypertension is a disease classified elsewhere. Therefore, code 425.8 should be added to 414.8 (other specified forms of chronic ischemic heart disease) for ischemic CMP.

But it’s ischemic heart disease. Wait a second.

Beware of encoders

What about a patient with left ventricular hypertrophy due to increased work caused by aortic stenosis? Physicians refer to this as valvular heart disease. In their minds, it’s a CMP. However, coders input “disease, valvular, heart” into an encoder and are directed to endocarditis, which is incorrect. Why does this occur? It occurs because encoders interpret words literally and as being part of one context. This means that a valvular disease of the heart must be endocarditis.

Instead, coders should report code 424.1 (aortic valve disorders) and 425.8 for valvular CMP. If a patient has advanced to chronic diastolic failure due to the valvular heart disease resulting from aortic stenosis, coders should add code 428.32.

Know the bottom line

In summary, consider the following:

Code 425.8 should accompany all identifiable and codeable diseases that affect the function of the heart and that don’t have a specific designation within the 425 code series

• Assign code 425.4 to all primary or idiopathic conditions of the heart that cause functional change
• Assign code 425.9 to all dysfunctions of the heart that you know are caused by an unidentifiable source
• Report code 425.4 only for primary CMP, which is intrinsic disease of the heart muscle not caused by other conditions

Editor’s note: Dr. Gold is CEO of DCBA, Inc., a consulting firm in Atlanta that provides physician-to-physician clinical documentation improvement programs, and is also a member of the ACDIS Advisory Board. Contact him at 770/216-9691 or via e-mail at rgold@DCBAInc.com.

This article was originally published in the December 2011 edition of Briefings on Coding Compliance Strategies.