CARDIOVASCULAR
2018 Universal Definition
of Myocardial Infarction
This article summarises the key messages from the Fourth Universal Definition of Myocardial Infarction
Martin Reindl
MD PhD
Sebastian Johannes
Reinstadler MD PhD
Bernhard Metzler
MD MSc
University Clinic of
Internal Medicine
III, Cardiology and
Angiology, Medical
University of Innsbruck,
Austria
In August 2018, the Joint European Society of
Cardiology (ESC)/American College of Cardiology
(ACC)/American Heart Association (AHA)/World
Heart Federation (WHF) Task Force published an
updated universal definition of myocardial
infarction (MI). 1 This consensus document
provides newly revised criteria for the definition
of MI 1 , driven by recent advances of modern
cardiology. So, what was new in this Fourth
Universal Definition of MI and how will this
consensus paper affect everyday clinical practice?
The condition
Coronary heart disease is one of the leading
causes of morbidity and mortality worldwide. 2
MI represents the most common, as well as
deleterious, form of coronary heart disease,
generating a high epidemiological and economic
burden of disease. 1,2 Considering the high
incidence and high global health burden,
establishing a general and uniform definition
of MI has been attempted over the last
decades. 1,3 However, different clinical
presentations as well as past and ongoing
diagnostic advances have given rise to different
definitions of MI, leading to controversy and
confusion in clinical practice. 1 The first general
definition of MI dates back to the 1950s, when
working groups from the World Health
Organization (WHO) established a MI definition
mainly on the basis of electrocardiographic (ECG)
criteria. 1,4 The introduction of cardiac biomarkers
with high discriminatory power has particularly
revolutionised the detection and diagnosis of
MI and necessitated revisions of the global MI
definition. 1 Modern high-sensitivity cardiac
troponin (cTn) assays allow both early detection
and fast rule out of MI, which is crucial in daily
clinical routine. 5,6 By contrast, however, the broad
implementation of high-sensitivity troponins into
routine laboratory testing has led to a sharply
increasing number of incidental findings of
elevated troponins without any clinical evidence
of ischaemia, frequently leading to clinical
misinterpretation. 5 The differentiation of such
a clinical scenario of myocardial injury without
ischaemia from actual MI was a central focus
of the newly revised 2018 Universal Definition
of MI. 1
Fourth Universal Definition of MI
According to the 2018 consensus document, MI is
defined as: (1) acute myocardial injury detected by
3
HHE 2019 | hospitalhealthcare.com
abnormal cardiac biomarkers; and (2), in a clinical
setting with evidence of myocardial ischaemia. 1
Abnormality of cardiac biomarkers is defined
by a detection of elevated cTn values with at least
one value above the 99th percentile upper
reference limit (URL). 1 If, in addition, a dynamic
rise and/or fall of cTn concentrations is detected,
the myocardial injury is considered as acute. 1
In contrast, a setting of persistently elevated cTn
levels without any dynamics would be referred to
as chronic myocardial injury. 1 Above and beyond
acute myocardial injury, evidence of acute
myocardial ischaemia is required for the
diagnosis of MI. One or more of the following
clinical features affirm acute myocardial
ischaemia: typical symptoms of myocardial
ischaemia; new ischaemic electrocardiographic
changes as well as development of pathological
Q waves; imaging evidence of new loss of viable
myocardium or new regional wall motion
abnormality; and identification of a coronary
thrombus by angiography or autopsy. 1
Primarily in light of revascularisation
strategies, in the early setting of acute coronary
syndrome a categorisation into ST-elevation
myocardial infarction (STEMI) and non-STEMI
is nowadays common clinical practice. 1 Beyond
these clinical categories used in the early stage,
MI can be classified in different types depending
on differences in clinical, pathological and
prognostic features. 1 In the fourth update of the
Universal Definition of MI, the five previously
proposed types of MI have undergone only slight
modifications. 1 The criteria of the different MI
types are summarised in brief below.
Type 1 MI
Type 1 MI describes the classical concept of
atherothrombotic MI caused by a disruption
(rupture or erosion) of an atherosclerotic plaque
on the basis of coronary artery disease. 1 The
resulting thrombus can either be occlusive
or non-occlusive. 1
Type 2 MI
The concept of type 2 MI is more complicated
and multifactoral, defined by myocardial
ischaemia due to a mismatch between oxygen
supply and oxygen demand unrelated to coronary
atherothrombosis. 1 This type of MI remains the
most challenging for clinicians because a plethora
of different clinical scenarios can lead to type 2
MI. Importantly, in contrast to coronary