Look to the I21 code series in most cases. Chest pain is one of the most common reasons that people visit EDs, and although not every patient presenting with this symptom will be diagnosed with a myocardial infarction (MI), it’s important to know how to code an MI when it occurs. When reporting an MI, you must know details such as if the patient had a ST elevation myocardial infarction (STEMI) or a non-ST elevation myocardial infarction (NSTEMI), as well as the age of the MI, for example. Otherwise, you won’t be able to select the most accurate diagnosis code. Keep these tips in mind when reporting MIs in your emergency department. Tip 1: Rely on These Codes for STEMIs You have numerous code options to report a Type 1 STEMI. They are as following: Don’t miss: Several of the codes also include many other diagnoses, so you should always double-check that information in your ICD-10-CM manual. For example, code I21.29 includes ten other diagnoses, including acute transmural myocardial infarction of other sites, acute apical-lateral transmural (Q wave) infarction, acute basal-lateral transmural (Q wave) infarction, and acute high lateral transmural (Q wave) infarction. STEMI defined: “A STEMI is caused by a complete blockage of an artery causing full thickness heart muscle damage. When a patient is having a STEMI, the electrocardiogram (ECG) will show elevations in the ST segment, thus the term STEMI — ST elevation myocardial infarction,” says Robin Peterson, CPC, CPMA, manager of professional coding with Pinnacle Integrated Coding Solutions, LLC. “Due to the loss of blood flow through the artery, complications such as life-threatening arrhythmias including ventricular fibrillation can occur, which accounts for a large percentage of deaths related to STEMIs,” Peterson says. The amount of time the vessel is occluded can directly affect the amount of heart muscle damage caused by the blockage, myocardial ischemia. Once the heart muscle is damaged, it will never repair itself and can often lead to other serious cardiac conditions as a result. Tip 2: Observe How to Report NSTEMIs If your provider documents a NSTEMI, you only have one code choice — I21.4 (Non-ST elevation (NSTEMI) myocardial infarction). Don’t miss: You should also report I21.4 for acute subendocardial myocardial infarction, non-Q wave myocardial infarction NOS, Nontransmural myocardial infarction NOS, and Type 1 non-ST elevation myocardial infarction. Don’t miss: If a type 1 NSTEMI evolves to a STEMI, you should report the appropriate STEMI code, per the guidelines. However, if a type 1 STEMI converts to a NSTEMI because of thrombolytic therapy, you should report this condition with a STEMI code. NSTEMI defined: “A NSTEMI is caused by a partial or near complete occlusion of a coronary artery and is usually identified by a rise in cardiac enzymes” Peterson says. Tip 3: Identify MI’s Age for Appropriate Code Choice When coding MIs, you must know the MI’s age because your code choice will depend upon this information. For example, if the MI is equal to or less than four weeks old and it meets ICD-10’s definition of “other diagnoses,” you should report the appropriate code from category I21-. This includes “transfers to another acute setting or a postacute setting,” per the guidelines. A recent MI is the most common type seen in the ED. Tip 4: Follow Numerous Rules for Subsequent Type 1, Unspecified MIs The guidelines offer multiple rules you should be aware of when reporting subsequent MIs. Rule 1: You should report a code from category I22- (Subsequent ST elevation (STEMI) and non-ST elevation (NSTEMI) myocardial infarction) when a patient who has previously had a type 1 or unspecified MI has a new MI within the four-week time frame of the initial MI. Rule 2: You must report a code from category I22- in conjunction with a code from category I21-, and the sequencing of these codes will depend upon the specific circumstances of the encounter. Take a look at this example from Peterson: A patient presents to the ED with a type 1 STEMI involving the left anterior descending coronary artery. He is treated and released. The patient then returns to the ED two weeks later with an acute type 1 NSTEMI. You should report codes I22.2 and I21.02 on this claim. Rule 3: You should only report a code from category I22- for a type 1 or unspecified subsequent MI. If the patient has a subsequent type 2 MI, you should report code I21.A1 (Myocardial infarction type 2). This code also includes an MI due to demand ischemia and an MI secondary to ischemic imbalance. Don’t miss: When you report code I21.A1, you should first code the underlying cause such as anemia (D50.0-D64.9),chronic obstructive pulmonary disease (J44.-), paroxysmal tachycardia (I47.0-I47.9), or shock (R57.0-R57.9). On the other hand, if the patient has a subsequent type 4 or type 5 MI, you should report code I21.A9 (Other myocardial infarction type). Code I21.A9 includes a myriad of other diagnoses including MI associated with revascularization procedure, type 3 MI, type 4a MI, type 4b MI, type 4c MI, and type 5 MI. Don’t miss: You also have a few coding notes to go along with I21.A9. For example, you should also code a complication, if known and applicable, such as acute stent occlusion (T82.897-), acute stent stenosis (T82.855-), acute stent thrombosis (T82.867-), cardiac arrest due to underlying cardiac condition (I46.2), complication of percutaneous coronary intervention (PCI) (I97.89), or occlusion of coronary artery bypass graft (T82.218-). Example: A patient presents with a type 2 NSTEMI three weeks after he was hospitalized, treated, and released for a type 1 STEMI involving the right coronary artery. You should report codes I21.A1 and I21.11 on your claim. Rule 4: If the patient has a subsequent MI of one type within four weeks of a MI of a different type, you should report the correct codes from category I21- to identify each type. However, you should not report a code from I22- in this case. Remember: You should only report a code from category I22- if the initial and the subsequent MI are type 1 or unspecified.