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Coding coronary artery stenosis marked by confusion

Unclear Coding Clinic advice regarding coronary artery stent stenosis has resulted in confusion about whether 996.72 (complication of internal cardiac device, implant, and graft) is the correct default code for cases often referred to as "in-stent stenosis" or "restenosis."

Physicians typically use these terms to indicate that a stent has become stenosed. More often than not, physicians do not describe the etiology or pathophysiology that results in the stenosis, experts say.

Understand the problem

At the center of the debate is a clarification written in Coding Clinic, third quarter, 2006, regarding advice given in the third quarter, 2002, issue. The question from 2002 concerned a patient with a history of coronary artery disease and "stenting of an isolated lesion of the left anterior descending artery, who began to have a recurrence of anginal symptoms," according to Coding Clinic. The patient had severe stenosis of a stent and a new occlusion of the diagonal artery, prompting off-pump coronary artery bypass grafts.

In its answer in 2002, Coding Clinic said that the principal diagnosis for this case is 414.01 (coronary atherosclerosis, of native coronary artery). But given the situation described in the question, the circumstances would also require coding the in-stent stenosis (996.72) as a secondary diagnosis, claims James S. Kennedy, MD, CCS, senior physician executive for FTI Healthcare in Brentwood, TN. This coding change would add a major cardiovascular diagnosis and could significantly change the DRG relative weight.

The 2002 answer prompted a follow-up question in Coding Clinic, third quarter, 2006, asking whether 996.72 was the correct principal diagnosis for the case, in light of the restenosis of the patient's coronary stent. According to the 2006 question, "The [2002] question does not specify this condition was caused by further progression of the patient's coronary atherosclerosis."

Coding Clinic answered in 2006 that 996.72 is not the correct code, reasoning that "the occlusions were caused by further progression of the disease, not scar tissue. The answers provided in Coding Clinic are based on specific medical record documentation." Unfortunately, the 2002 Coding Clinic did not mention in its narrative that the stenosis is a result of the progression of the disease, Kennedy says. However, Coding Clinic added this information into its 2006 answer.

This new answer-plus the fact that past Coding Clinics (e.g., first quarter, 2000; third quarter, 2001) have assigned 996.72 in cases of in-stent stenosis due to scar tissue-has caused some coders to conclude that the link to scar tissue has to be explicit in the documentation before they can assign 996.72, says Marty Beckman, RHIT, CCS, a nosologist for 3M Health Information Systems in St. Paul, MN.

Consider a possible answer

Sherry Stiltner, RHIT, documentation improvement specialist for Mountain States Health Alliance in Johnson City, TN, sympathizes with this view. "If you go into the 3M coder and code 'restenosis' or 'in-stent stenosis,' it takes you to 996.72. So, I feel like if that's where it's sending us, that's what we should use," she says.

However, Stiltner says that her facility has received clarification from Coding Clinic that might contradict this view. According to Stiltner, a Mountain States facility received the following from the Coding Clinic editorial board in response to a question regarding the topic of in-stent stenosis:

Code assignment is always based on the physician documentation. When the physician indicates restenosis is caused by progression of coronary artery disease, assign a code from category 414.0x, coronary atherosclerosis. However, when the physician specifies stenosis is from formation of scar tissue secondary to the body's normal reaction to the insult of the stent, assign code 996.72. If the cause of the stenosis cannot be established based on the available medical documentation, the physician should be queried for clarification.

Stiltner says this answer will appear in the upcoming second-quarter 2007 Coding Clinic (note, however, that this is not guaranteed, as any of the cooperating parties could reopen the topic, resulting in delay). As a result, Stiltner's compliance department has put in place a query and education process that makes it clear that the only time coders can use 996.72 is when the physician documents a complication of the stent or scar tissue formation, which happens infrequently. "Physicians don't like to say 'complication,' " she says.

Examine other views

Kennedy, for one, is not happy with this potential Coding Clinic advice. "Coding Clinic [would be] wrong to not allow the coder to code 'in-stent' stenosis not otherwise specified [NOS] as 996.72, given that the science of 'in-stenosis' is that nearly all procedures are due to neointimal (scar) tissue and that ICD-9-CM specifically assigns all nonoccluded in-stent stenoses to category 996.7," he says. The only time the ICD-9-CM table allows use of atherosclerosis codes for in-stent disease is in total occlusion due to atherosclerosis (note the 996.72 exclusion), he adds.

Kennedy points to previous Coding Clinic articles-especially first quarter, 2000, and third quarter, 2001-indicating that coronary artery stent stenosis NOS falls into 996.72. In addition, Coding Clinic, first quarter, 2007 mentioned, in response to a question about postoperative anemia, that "the directives in the ICD-9-CM Manual take precedence over advice published in Coding Clinic."

"ICD-9-CM trumps Coding Clinic--end of story," says Kennedy. "Would a hospital be wrong to code 996.72 for 'in-stent stenosis NOS' without a query? Could the recovery audit contractors potentially disallow this ICD-9-CM-driven code should the hospital not query the physician, given Coding Clinic's directive?" he asks. "No, and yes. To clear the air, Coding Clinic needs to revise its advice and support ICD-9-CM." Beckman points to the ICD-9-CM index as further proof that 996.72 is the default code in these situations. If you look in the index under occlusion of coronary stent, the index directs to you 996.72.

Beckman also points out that the purported Coding Clinic answer doesn't fully answer the question. "I can never argue against querying for more clarification of a diagnosis," he says. "However, this could be burdensome for coders (and physicians) because in-stent stenosis is a fairly common diagnosis. The other problem is that physicians don't always respond to queries, which would still leave you with the task of establishing a default code for restenosis." Faced with that task, Beckman would then argue for assigning 996.72.

Editor's note: This article was adapted from the May 2007 issue of Briefings on Coding Compliance Stategies. For more information on this publication, click here

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