Q&A: AMI and circulatory principal diagnoses

Q: I recently heard an example where there was a patient with a principal diagnosis of lower extremity deep vein thrombosis (DVT) and myocardial infarction, which was not present on admission. In the example, they said that this case would go to DRG 282, Acute myocardial infarction (AMI) without a CC/MCC, even though the AMI was not present on admission and the DVT was. Can you explain why it would be coded to this DRG?

A: First, I must tell you that not everything in CDI makes perfect sense, clinically or otherwise, and we have to be a bit flexible and roll with the punches. Secondly, there will always be some type of exception to every rule you are taught. Your question is a perfect example of one of those exceptions.

It’s confusing in this example that the AMI that was not present on admission (POA) would impact the DRG assignment. This doesn’t even make sense because the definition of a principal diagnosis states that it must be present on admission. Based on the principal diagnosis, the CDI professional will choose the proper working DRG.

That said, there’s a strange thing that happens when a circulatory diagnosis is the principal diagnosis and the patient suffers an AMI while in the hospital. An AMI is what I like to call the ultimate DRG driver in the circulatory chapter (and only in the circulatory chapter). If a patient is admitted with any diagnosis that is found in the circulatory chapter (e.g. DVT, heart failure, or a peripheral vascular disorder) and then suffers an AMI while in the hospital, the AMI becomes the driver of the DRG assignment. This means that you will end up in DRGs 280, 281, 282 when the patient’s discharge status is “alive,” or DRGs 283, 284, 285 if the patient’s discharge status is “expired.” Your principal diagnosis will remain the DVT, and unfortunately, you will not be able to use it as a CC/MCC, but the DRG assignment will go from 294/295 to one of the AMI DRGs. Remember, only secondary diagnoses are considered CC/MCCs, not principal diagnoses.

Another example would be a patient admitted for heart failure (which would allow for the assignment of DRGs 291, 292, 293 depending on the presence of a CC/MCC). While still in the hospital, the patient suffers an AMI. In this example, the heart failure is still the principal diagnosis, but the AMI takes over driving the DRG assignment and you will now go to one of the AMI DRGs based on whether the patient expires or lives.

It's important to note that this does not occur with any other principal diagnoses found in any other chapters/body systems with an AMI occurring during an inpatient stay. If the patient was admitted with esophageal varies, for example, the principal diagnosis would lead you to DRGs 368, 369, 370, Major Esophageal Disorders, and the final determination would be based on the addition of a secondary diagnosis being either a CC or an MCC. If this same patient suffered an AMI during their stay, the AMI would serve as an MCC. It would not change the DRG assignment, so your final DRG would be DRG 368, Major Esophageal Disorders with an MCC.

Editor’s Note: Sharme Brodie, RN, CCDS, CCDS-O, CDI education specialist and CDI Boot Camp instructor for HCPro in Middleton, Massachusetts, answered this question. For information, contact her at sbrodie@hcpro.com. For information regarding CDI Boot Camps, click here.