June 2013

Coding for Acute Coronary Syndrome
For The Record
Vol. 25 No. 9 P. 35

Acute coronary syndrome (ACS) is an umbrella term used to describe chest pain caused by either an acute myocardial infarction (AMI) or unstable angina. When myocardial cells do not receive adequate blood flow or oxygenation, one of the following conditions may occur: myocardial ischemia, myocardial injury, or myocardial infarct.

ACS is classified to ICD-9-CM code 411.1, which is the same code assigned for unstable angina. It is vital to review the entire medical record to make sure the information presented supports the final code assignment. Therefore, if the record contains evidence that the patient may have experienced an AMI but only ACS is documented, then it may be appropriate to query the physician for clarification of the final diagnosis. Final code assignment always is based on physician documentation.

MI is the death of myocardial tissue usually caused by a blocked coronary artery. AMI is classified to ICD-9-CM category 410. A fourth and fifth digit are needed to completely code the condition.

Physicians are increasingly classifying AMI based on type. The European Society of Cardiology, the American College of Cardiology, the American Heart Association, and the World Heart Federation created a task force to update the 2000 consensus document regarding MI classification. Since this update, physicians have been documenting “type II MI” with increasing frequency. Unfortunately, they may use this term to refer to myocardial injury or ischemia, not infarct. However, because MI is documented, type II MI is assigned to the AMI codes (category 410).

Physician clarification regarding whether the cardiac event was ischemia, injury, or infarct is essential in determining what insult has occurred to the myocardium. Possible alternate language to describe the supply-demand mismatch described in type II MI (where the provider has determined there was no MI) would be demand ischemia or unstable angina.1

Demand ischemia (411.89) is a transitory imbalance that may be caused by exercise, tachycardia, or emotion. It is characterized by angina because of the increased oxygen demand.2 Demand ischemia may clinically reflect a troponin elevation where myocardial tissue has not been injured or necrosed. The condition frequently is confused with type II MI in the clinical setting, and clarification may be needed to determine an accurate diagnosis reflective of elevated troponins and/or other relevant clinical indicators and treatment.

The signs and symptoms of ACS are similar to those of AMI and if the condition is not treated quickly, it will progress to an AMI. Common signs and symptoms of ACS include chest pain or discomfort that may be described as burning, pressure, tightness, or fullness and referred pain to one or both arms or shoulders and the jaw, neck, back, or stomach.

When a patient arrives in the emergency department with a chief complaint of chest pain, the physician immediately will order an electrocardiogram (EKG) and blood tests. The EKG may show an AMI has occurred or is in progress. The blood tests measure the heart enzymes that leak into the blood if the heart has been damaged by an AMI. According to the Mayo Clinic, other diagnostic studies the physician may order include an echocardiogram, a chest X-ray, a nuclear scan, a CT angiogram, or cardiac catheterization.

ACS treatment, according to the Mayo Clinic, depends on the symptoms and the degree of artery blockage. Medications used for treating ACS include aspirin, thrombolytics, nitroglycerin, beta blockers, angiotensin-converting enzyme inhibitors and angiotensin receptor blockers, calcium channel blockers, statins, and clopidogrel. More invasive treatment may involve angioplasty with stenting and a coronary artery bypass graft.

Coding and sequencing for ACS are dependent on the physician documentation in the medical record and application of the Official Coding Guidelines for inpatient care. Also, use specific AHA Coding Clinic for ICD-9-CM and American Medical Association CPT Assistant references to ensure complete and accurate coding.

— This information was prepared by Audrey Howard, RHIA, and Cheryl Manchenton, RN, senior consultants with 3M Consulting Services. 3M Consulting Services is a business of 3M Health Information Systems, a supplier of coding and classification systems to more than 5,000 health care providers. The company and its representatives do not assume any responsibility for reimbursement decisions or claims denials made by providers or payers as the result of the misuse of this coding information. More information about 3M Health Information Systems is available at www.3mhis.com or by calling 800-367-2447.

References
1. Thygesen K, Alpert JS, White HD. Universal definition of myocardial infarction. Eur Heart J. 2007;28(20):2525-2538.
2. Booker KJ, Holm K, Drew BJ, et al. Frequency and outcomes of transient myocardial ischemia in critically ill adults admitted for noncardiac conditions. Am J Crit Care. 2003;12(6):508-516.

ICD-10-CM Coding for ACS and Other Ischemic Diseases
The diagnosis of acute coronary syndrome (ACS) is classified to code I24.9, Acute ischemic heart disease, in ICD-10-CM. The condition is indexed as “Syndrome, coronary acute NEC [not elsewhere classified].” Since NEC is included, if the condition is classified elsewhere, such as angina or myocardial infarction, it is appropriate to assign the more specific code. However, if ACS is not better classified elsewhere, assign code I24.9.

Demand ischemia is indexed to code I24.8. However, there is a “see also Angina” note. A see also note indicates another term may be referenced to find a more accurate code, but it is not mandatory to follow the note if the original main term provides the necessary code. If the record does not indicate more to a condition, then assigning code I24.8 for demand ischemia may be appropriate.

Angina is classified to category I20. There is an Excludes 1 note associated with the angina category code that excludes angina with atherosclerosis of the coronary arteries of native, bypassed, or transplanted vessels. If the physician documents that the patient has angina as well as coronary atherosclerosis, a code from one of the following subcategories should be assigned:

• I25.11-, Atherosclerotic heart disease of native coronary artery with angina pectoris with documented spasm; or

• I25.7-, Atherosclerosis of coronary artery bypass graft(s) and coronary artery of transplanted heart with angina pectoris.

A causal relationship can be assumed in a patient with both atherosclerosis and angina pectoris unless the physician documentation indicates that the angina is caused by something other than the atherosclerosis. If a patient has angina and there is no documentation of atherosclerosis of a coronary artery, an applicable code from the I20 category would be assigned.

— AH, CM