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Previously undiagnosed myocardial infarction

Jason Tarkin, MBBS, MRCP
Gerald S Bloomfield, MD, MPH
Section Editor
Juan Carlos Kaski, DSc, MD, DM (Hons), FRCP, FESC, FACC, FAHA
Deputy Editor
Gordon M Saperia, MD, FACC


Incidental findings are common in medicine and often lead to diagnostic and management dilemmas. This topic discusses one such patient group: asymptomatic individuals who are found to have a previously undiagnosed myocardial infarction (MI).


According to the Third Universal Definition of MI, a silent MI is defined in an asymptomatic patient by new electrocardiogram Q wave criteria for MI or evidence of MI on cardiac imaging, which are not directly attributable to a coronary revascularization procedure [1]. (See "Criteria for the diagnosis of acute myocardial infarction", section on 'Prior MI'.)

The term "previously undiagnosed" MI is used synonymously to describe either a "silent" MI, when no symptoms are recalled by the patient, or an "unrecognized" MI in a patient who, despite experiencing atypical symptoms related to their MI, did not seek medical attention at that time as they did not recognize their symptoms to be harmful. The literature has used both of these terms interchangeably over the last few decades. In either case, owing to a lack of classic symptoms, there is an invariable delay in diagnosis and treatment of these patients, and often the MI will go undiscovered for months or even years.

Patients who present with symptoms or late complications of a "missed" MI (a term that refers to an individual with chest pain that is inappropriately managed as a noncardiac cause and subsequently found to have sustained an acute MI within the next 24 to 48 hours) represent a different patient cohort [2-4]. The approach to these patients is discussed separately. (See "Overview of the acute management of ST-elevation myocardial infarction" and "Overview of the non-acute management of ST elevation myocardial infarction" and "Overview of the acute management of non-ST elevation acute coronary syndromes" and "Overview of the non-acute management of unstable angina and non-ST elevation myocardial infarction".)


There are two principal clinical scenarios in which a previously undiagnosed MI might be suspected. This diagnosis is most commonly associated with the finding of an abnormal electrocardiogram (ECG) with significant abnormalities, usually pathological Q waves, discovered incidentally during a routine health checkup [5,6]. Persistent ST-segment and T wave ECG abnormalities, though less specific for MI than Q waves, can also be signs of prior MI in asymptomatic patients. In this scenario, ECG patterns suggestive of prior MI are often identified by ECG machines with automated interpretation (eg, "cannot exclude anterior MI").

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Literature review current through: Oct 2017. | This topic last updated: Jul 11, 2017.
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