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Acute MI due to Coronary Artery Stent Stenosis: Coding Challenges

March 4, 2022

In our recent Cause and Effect webinar we described the ICD-10 E/M convention for which, in certain conditions, the etiology (cause) must be assigned as the principal diagnosis followed by the manifestation (effect).  For example, with malignant pleural effusion, code first the neoplasm.

For patients admitted with acute myocardial infarction due to stent stenosis, the E/M convention applies. The ICD-10 classification instructs us to “code first (if applicable)” I97.190, Other postprocedural cardiac functional disturbance following cardiac surgery, when associated with I21.A9, Other myocardial infarction, and T82.855A, Stenosis of coronary artery stent.

We were asked whether code I97.190 should be assigned only when it occurs intraoperatively or following a recent coronary artery stent insertion.

Code I97.190 as principal diagnosis is supported by:

  1. As noted above, the ICD-10 coding convention “etiology/manifestation” instructs us to “code first, if applicable” I97.190 when assigning code I21.A9 for an acute MI.

    Code I21.A9 includes Type 3, 4, and 5 myocardial infarctions and any MI associated with revascularization procedure. Type 4 myocardial infarctions are "related to" PCI, stent thrombosis, and restenosis of the stent, and Type 5 is related to CABG. Therefore, I97.190 would be “applicable” to any of these except a Type 3 myocardial infarction, which is defined as “MI resulting in death when biomarker values are unavailable.”
  2. Code I97.190, Other postprocedural cardiac functional disturbance following cardiac surgery, includes both “postprocedural” and “following cardiac surgery.” There is no defined time frame for “postprocedural” or “following cardiac surgery”. The classification does not define a time limit for the development of a complication. It may occur during the hospital episode in which the surgery was performed, shortly thereafter, or years later (Coding Clinic 2002 Second Quarter p. 12-13).
  3. In Coding Clinic 2019 Second Quarter p. 32, in response to a question regarding the “correct diagnosis codes and sequencing of an acute myocardial infarction (MI) due to stent thrombus following coronary angioplasty and stent placement,” Coding Clinic advised to assign code I97.190 as principal diagnosis followed by codes T82.855A and I21A9.  

Although assigning both the I97 and the T-code appears redundant since both are complication codes, and the T code specifically describes the stent complication, the ICD-10 classification requires the I97 code to be assigned as principal diagnosis.

Apparently conflicting with the 2019 Coding Clinic advice and the ICD-10 classification are two 2021 Coding Clinics regarding the same circumstances which do not include the I97.190 code. One of the 2021 Coding Clinics addressed a physician diagnosis of the “culprit lesion” essentially saying it identifies the lesion causing an MI. The other involves an MI due to both stent stenosis and progression of native CAD. The omission of I97.190 appears to have been an oversight by the 2021 Coding Clinics since the ICD-10 classification takes precedence. This discrepancy should be explained by Coding Clinic. 

It is important to distinguish in-stent stenosis/restenosis, thrombosis, or total occlusion of a stent from progression of coronary artery disease (CAD) which occurs in a native vessel or graft and does not apply to stents. 

Bottom line, from a DRG assignment standpoint, whether the I97 code or the specific T82 code is assigned as principal diagnosis, the resulting DRG assignment is DRG 246 with the MI as an MCC.  Either the I97 code is assigned (code first) or T code since any treatment or procedure will be directed to the T code stent complication (stenosis, thrombosis), not the myocardial infarction.

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