6 ACPHOSPITALIST January 2014

ACUTE CORONARY SYNDROME: A CARDIAC CONUNDRUMBy Richard Pinson, MD, FACP

diagnosed when there is no biomarker release based on 2 samplescollected at least 6 hours apart.

Keep in mind the many causes of elevated troponin levelsthat do not necessarily indicate MI, such as heart failure, renalfailure, arrhythmias, myocarditis, pulmonary embolism, anduneventful coronary procedures. Clinical presentation and otherdiagnostic studies will help to rule out these alternative diagnoses.

The guidelines also say that a provisional diagnosis of ACSshould be further classified following evaluation as:

1. STEMI requiring consideration of immediate reperfusiontherapy or percutaneous coronary intervention (PCI),

2. NSTEMI,3. UA (definite, probable, or possible),4. Non-ACS cardiovascular condition (for example, peri-

carditis), or5. Non-cardiac condition with a specific cause (for example,

gastroesophageal reflux disease) or with unknown cause.Following this guideline from the AHA and ACC, coding

rules classify UA and ACS as the same condition assigned to alow-severity, low-complexity diagnostic code. NSTEMI—even ifcharacterized as mild or “early”—is classified as an acute MI, amore serious and complex diagnosis.

Finally, where does demand ischemia fit into the picture? Thisterm is often used indiscriminately to describe patients with evi-dence of myocardial ischemia associated with a mismatch betweenmyocardial oxygen demand and supply, but without coronaryartery disease (CAD) or at least not primarily due to CAD. The diag-nosis of “demand ischemia” is sometimes used when patientsexperience release of cardiac biomarkers, like troponin.

However, the Third Universal Definition of MyocardialInfarction (Circulation. 2012;126:2020-2035), developed jointlyand published by the ACC, AHA, European Society ofCardiology and World Heart Foundation, defines “MI type 2” as“myocardial injury with necrosis [recognized by cardiac biomarker

CODING CORNER

“Acute coronary syndrome” (ACS) encompasses a continu-um of myocardial ischemia and infarction, which can

make the diagnostic and coding criteria for ACS confusing.What’s more, coding definitions and requirements don’t alwaysmatch clinical practice and terminology. Physicians should viewthe ACS diagnosis as provisional and evaluate further for a spe-cific diagnosis.

Narrowing the diagnosis starts with knowing the guidelines.The most recent American Heart Association (AHA)/AmericanCollege of Cardiology (ACC) Guidelines for the Management ofPatients with Unstable Angina/Non-ST-Elevation MyocardialInfarction (NSTEMI) establish ACS as a provisional diagnosticterm encompassing “clinical symptoms that are compatible withacute myocardial ischemia.” The term includes myocardial infarc-tion (ST-segment elevation and depression, Q wave and non-Qwave) and unstable angina (UA). The more severe conditions ofST-elevation myocardial infarction (STEMI) and Q-wave infarctionare not discussed here as part of the ACS definition.

NSTEMI and UA are a part of the ACS continuum consideredto have similar pathogenesis and clinical presentations but differ-ent severity, as defined by the release of cardiac biomarker(s) suchas troponin I, troponin T or CK-MB (creatine kinase muscle orbrain type). According to the guidelines, “NSTEMI is established ifa biomarker has been released” at any time to a level above “the99th percentile reference limit of the normal population.” UA is

Tachy- and bradyarrhythmias

Aortic dissection

Severe aortic valve disease

Hypertrophic cardiomyopathy

Shock: cardiogenic, hypovolemic, septic

Severe anemia

Hypertensive crisis

Coronary spasm

Coronary embolism or vasculitis

Coronary endothelial dysfunction without CAD

Source: Circulation 2012; 126: 2020-2035

Table 1. Causes of type 2 myocardial infarction

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