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Open Access Journal of Cardiology Research Article 8 min read

Myocardial Injury: an Umbrella Diagnosis of Confusion

Jogu HR*
* Corresponding author
ISSN: 2578-4633  10.23880/oajc-16000149  Received: January 27, 2020  Published: February 14, 2020
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Keywords
Myocardial Injury Umbrella Diagnosis Upper Reference Level
Abstract

The first description of myocardial infarction (MI) in the history of medical literature was in the late 19th century by Hammer, et al. It was not until the late 20th century, the first unified definition of MI was proposed by the working group of the World Health Organization based on electrocardiogram. Later, the definition of MI has advanced towards using both clinical and biochemical approaches after the development of more validated cardiac troponin (cTn).

Abbreviations

MI: Myocardial Infarction; cTn: Cardiac Troponin; UDMI: Universal Definition of Myocardial Infarction; NIMI: Nonischemic Myocardial Injury; URL: Upper Reference Level

Short Communication

The first description of myocardial infarction (MI) in the history of medical literature was in the late 19th century by Hammer, et al. [1]. It was not until the late 20th century, the first unified definition of MI was proposed by the working group of the World Health Organization based on electrocardiogram [2]. Later, the definition of MI has advanced towards using both clinical and biochemical approaches after the development of more validated cardiac troponin (cTn) [3]. In 2007 a Universal Definition of Myocardial Infarction (UDMI) consensus document introduced 5-subtypes of MI recognizing etiologically distinctive causes and was further refined in 2012 [4, 5]. In addition to the 5-subtypes of MI, many more categories have been identified with elevated cTn but without cardiac ischemia. To include those additional diversified groups of cohorts, in 2018, UDMI additionally introduced the terms “myocardial injury” and “Nonischemic myocardial injury” (NIMI) [6].

Myocardial injury is an umbrella term that broadly represents all the cases of elevated cTn with at least one value above the 99th percentile of the upper reference limit (URL) derived from a normal reference population. Myocardial injury is a large diagnostic category, and it does not specify any underlying pathophysiology or mechanism of the injury. The spectrum of myocardial injury is from no myocardial injury to myocardial injury itself to MI and NIMI. Myocardial injury may be acute; which manifests as a raising and/ or falling pattern, or chronic; in which cTn is persistently elevated or changes minimally with serial measurements. The diagnosis of MI is applied when there are any overt signs of clinical myocardial ischemia in patients with acute myocardial injury. Diagnosing myocardial ischemia is a crucial step in making distinctions among these categories. Diagnosis for myocardial ischemia is made if at least 1 of the following is observed: symptoms of myocardial ischemia, new ischemic electrocardiogram, new or presumably new regional wall motion abnormalities on echocardiogram, or acute coronary thrombus on coronary angiography [6]. MI is further subclassified based on underlying suspected pathophysiology as type 1-5. In those, Type 1 MI results from atherosclerotic plaque pathology, whereas type 2 MI from the conditions reflecting an imbalance between myocardial oxygen supply and demand, such as hypoxia, anemia, hypotension, bradyarrhythmia, tachyarrhythmias, and hypertension [6]. NIMI, on the other hand, is diagnosed when there is no evidence of overt myocardial ischemia [6, 7], and it may be acute NIMI; in the setting of dynamic raise and/or fall cTn pattern such as acute heart failure, pulmonary embolism, myocarditis, acute renal failure, sepsis, rhabdomyolysis, and extreme exertion, or chronic NIMI in the circumstances where cTn is persistently elevated without any signs or symptoms of cardiac ischemia, such as chronic heart failure, infiltrative cardiomyopathy, chronic renal failure, and valvular heart disease (Figures 1 & 2).

Over the last decade, cTn assays have become increasingly sensitive and improved its analytical performance. The higher tissue specificity, subsequently increased number of positive cTn patients with >99th percentile URL who had previously unrecognized myocardial injury [8, 9, 10]. However, the optimal approach to classify those patients into etiologically different categories remained uncertain until 4th UDMI introduced myocardial injury, acute NIMI, and chronic NIMI [6, 9]. Recent studies have reported that NIMI was not only found to be associated with an increased risk of all- cause mortality, cardiovascular mortality, MI, heart failure, and stroke [11, 12] but also its mortality was comparable to type 1 MI [13]. Data on optimal treatment in the NIMI is different from type 1 MI and limited due to heterogeneous nature with varying triggers [14, 15, 16, 17, 18, 19]. These groups urgently required protocols to attenuate the underlying injury. To improve the understanding of the mechanism of this distinct category, NIMI and myocardial injuries, and to compare the existing results across the relevant literature, it is vital to identify and classify NIMI patients accurately.

Figure 1: Myocardial Injury Classification.
Click to enlarge
Figure 1: Myocardial Injury Classification.
Figure 2: Myocardial Injury flow chart.
Click to enlarge
Figure 2: Myocardial Injury flow chart.

Disparities were noticed in categorizing these entities optimally across the literature both prior and after the 4th UDMI definition, which represents a significant opportunity for confusion [20]. Many studies have categorized patients experiencing NIMI as a myocardial injury category [11, 21, 22, 23, 24, 25, 26, 27, 28, 29]. In those, some of them were published before the fourth UDMI document release [11, 21, 22, 25, 26], and some even after 4th UDMI definition [24, 28]. This has brought vagueness among the researchers and clinicians. Studies have shown that a significant number of patients have been categorized inadvertently into different category; 24.5% of NIMI patients in Chapman, et al. [11] 69% of NIMI patients in Scotland study [26] 69% of NIMI patients in Sarkisian, et al. [21] 56% of NMI patients in Sandoval, et al. [22] were classified as myocardial injury. Similarly, 57.2% of non-acute coronary syndrome patients [25] were categorized as myocardial injury.

However, very few studies have defined myocardial injury correctly as any abnormally elevated cTn levels >99the percentile URL irrespective of underlying pathology, according to 4th UDMI definition [7, 13, 20, 30]. Even though optimal evaluation and treatment for these groups have yet to be defined [7, 13] nonetheless, it is imperative for the researchers and clinicians to diagnose and categorize these important entities appropriately.

Conflicts of Interest

The Author declares no potential conflict of interests.

References

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@article{jogu2020,
  title   = {Myocardial Injury: an Umbrella Diagnosis of Confusion},
  author  = {Jogu HR},
  journal = {Open Access Journal of Cardiology},
  year    = {2020},
  volume  = {4},
  number  = {1},
  doi     = {10.23880/oajc-16000149}
}
Jogu HR (2020). Myocardial Injury: an Umbrella Diagnosis of Confusion. Open Access Journal of Cardiology, 4(1). https://doi.org/10.23880/oajc-16000149
TY  - JOUR
TI  - Myocardial Injury: an Umbrella Diagnosis of Confusion
AU  - Jogu HR
JO  - Open Access Journal of Cardiology
PY  - 2020
VL  - 4
IS  - 1
DO  - 10.23880/oajc-16000149
ER  -