Myocardial scarring

Inferior left ventricle wall scar, short axis echocardiography view

Myocardial scarring is the accumulation of fibrous tissue resulting after some form of trauma to the cardiac tissue.[1][2] Fibrosis is the formation of excess tissue in replacement of necrotic or extensively damaged tissue. Fibrosis in the heart is often hard to detect because fibromas, scar tissue or small tumors formed in one cell line, are often formed.[3] Because they are so small, they can be hard to detect by methods such as magnetic resonance imaging.[1] A cell line is a path of fibrosis that follow only a line of cells.

## Contents

* 1 Causes
* 1.1 Myocardial infarction
* 1.2 Coronary heart disease
* 1.3 Birth defect repairs
* 2 Formation
* 3 References

## Causes

### Myocardial infarction

A myocardial infarction, also known as a heart attack, often result in the formation of fibrosis.[2] A myocardial infarction is an ischemic event, or a restriction of blood flow to body tissue, such as by atherothrombosis.[4] Without blood flow to the myocardium, it is deprived of oxygen, causing tissue death and irreversible damage.[5] The tissue destroyed by the infarction is replaced with non-functioning fibrosis, restoring some of the structural integrity of the organ but resulting in impaired myocardial function.[6]

### Coronary heart disease

Coronary heart disease, also known as coronary artery disease, is one of the most common causes of myocardial damage, affecting over three million people in the United States.[7] In coronary heart disease, the coronary arteries narrow due to the buildup of atheroma or fatty deposits on the vessel walls. The atheroma causes the blood flow of the arteries to be restricted.[6] By restricting the blood flow, the tissue is still receiving some oxygen, but not enough to sustain the tissue over time.[5] The accumulation of the fibrotic tissue is much slower in coronary heart disease compared to an infarction because the tissue is still receiving some oxygen.[6]

### Birth defect repairs

Another form of myocardial scarring results from surgical repairs.[2] Surgical repairs are often necessary for a person born with a congenital defect of the heart.[8] While surgical laparoscopy still leaves myocardial scarring, the trauma seems to be less damaging then naturally occurring scarring.[2]

## Formation

Immediately after damage to the myocardium occurs, the damaged tissue becomes inflamed. Inflammation is the accumulations of neutrophils, macrophages, and lymphocytes at the site of the trauma.[9][10] In addition, "inflammatory cells upregulate the release of a myriad of signaling cytokines, growth factors, and hormones including transforming growth factor β, interleukins 1, 2, 6, and 10, tumor necrosis factor α, interferon γ, chemokines of the CC and CXC families, angiotensin II, norepinephrine, endothelin, natriuretic peptides, and platelet-derived growth factors".[10] Both the necrotic cells and the inflamed myocardium secrete and activate matrix metalloproteinase. Metalloproteinase aids in the destruction and reabsorption of necrotic tissue. After several days, collagen accumulation at the site of injury begins to occur.[10] As part of the extracellular matrix, granulated tissue consisting of fibrin, fibronectin, laminin, and glycosaminoglycan is suspended in a collagen base.[10] The extracellular matrix acts as scaffolding for the fibrillar collagen to form. The fibrillar collagen is the main constitute of what will become the scar tissue.[10]

## References

1. ↑ 1.0 1.1 Guler, Gamze Babur (2011). "Myocardial Fibrosis Detected by Cardiac Magnetic Resonance Imaging in Heart Failure: Impact on Remodeling, Diastolic Function and BNP Levels". Anatolian Journal of Cardiology 11 (1): 71–76. doi:10.5152/akd.2011.013. PMID 21220243.
2. ↑ 2.0 2.1 2.2 2.3 Fomovsky, Gregory M. (2010). "Evolution of Scar Structure, Mechanics, and Ventricular Function after Myocardial Infarction in the Rat". American Journal of Physiology. Heart & Circulatory Physiology 298 (1): 1–12. doi:10.1152/ajpheart.00495.2009. PMID 19897714.
3. ↑ (in en).
4. ↑ Katz, Monica Y. (2014). "Three-Dimensional Myocardial Scarring along Myofibers after Coronary Ischemia-Reperfusion Revealed by Computerized Images of Histological Assays". Physiological Reports 2 (7): 1–3. doi:10.14814/phy2.12072. PMID 25347856.
5. ↑ 5.0 5.1 (in en).
6. ↑ 6.0 6.1 6.2 Liang, Cuiping (2019). "Influence of the Distribution of Fibrosis within an Area of Myocardial Infarction on Wave Propagation in Ventricular Tissue". Scientific Reports 15 (1): 1–24. doi:10.1038/s41598-019-50478-5. PMID 31578428. Bibcode: 2019NatSR...914151L.
7. ↑ (in en).
8. ↑ CDC (2019-11-22). "What are Congenital Heart Defects? | CDC" (in en-us). https://www.cdc.gov/ncbddd/heartdefects/facts.html.
9. ↑ Radauceanu, Anca (2007). "Residual Stress Ischemia Is Associated with Blood Markers of Myocardial Structural Remodeling". European Journal of Heart Failure 9 (4): 370–376. doi:10.1016/j.ejheart.2006.09.010. PMID 17140850.
10. ↑ 10.0 10.1 10.2 10.3 10.4 Richardson, William J.; Clarke, Samantha A.; Quinn, T. Alexander; Holmes, Jeffrey W. (2015-09-20). "Physiological Implications of Myocardial Scar Structure". Comprehensive Physiology 5 (4): 1877–1909. doi:10.1002/cphy.c140067. ISSN 2040-4603. PMID 26426470.

* v
* t
* e

Cardiovascular disease (heart) (I00–I52, 390–429)

Ischaemic|

| Coronary disease|

* Coronary artery disease (CAD)
* Coronary artery aneurysm
* Spontaneous coronary artery dissection (SCAD)
* Coronary thrombosis
* Coronary vasospasm
* Myocardial bridge

|

Active ischemia|

* Angina pectoris
* Prinzmetal's angina
* Stable angina
* Acute coronary syndrome
* Myocardial infarction
* Unstable angina

Sequelae|

* hours
* Hibernating myocardium
* Myocardial stunning
* days
* Myocardial rupture
* weeks
* Aneurysm of heart / Ventricular aneurysm
* Dressler syndrome

Layers|

| Pericardium|

* Pericarditis
* Acute
* Chronic / Constrictive
* Pericardial effusion
* Cardiac tamponade
* Hemopericardium

|

Myocardium|

* Myocarditis
* Chagas disease
* Cardiomyopathy
* Dilated
* Alcoholic
* Hypertrophic
* Tachycardia-induced
* Restrictive
* Loeffler endocarditis
* Cardiac amyloidosis
* Endocardial fibroelastosis
* Arrhythmogenic right ventricular dysplasia

Endocardium /
valves|

| Endocarditis|

* infective endocarditis
* Subacute bacterial endocarditis
* non-infective endocarditis
* Libman–Sacks endocarditis
* Nonbacterial thrombotic endocarditis

|

Valves|

* mitral
* regurgitation
* prolapse
* stenosis
* aortic
* stenosis
* insufficiency
* tricuspid
* stenosis
* insufficiency
* pulmonary
* stenosis
* insufficiency

Conduction /
arrhythmia|

| Bradycardia|

* Sinus bradycardia
* Sick sinus syndrome
* Heart block: Sinoatrial
* AV
* 1°
* 2°
* 3°
* Intraventricular
* Bundle branch block
* Right
* Left
* Left anterior fascicle
* Left posterior fascicle
* Bifascicular
* Trifascicular
* Adams–Stokes syndrome

|

Tachycardia
(paroxysmal and sinus)|

| Supraventricular|

* Atrial
* Multifocal
* Junctional
* AV nodal reentrant
* Junctional ectopic

|

Ventricular|

* Accelerated idioventricular rhythm
* Catecholaminergic polymorphic
* Torsades de pointes

Premature contraction|

* Atrial
* Junctional
* Ventricular

Pre-excitation syndrome|

* Lown–Ganong–Levine
* Wolff–Parkinson–White

Flutter / fibrillation|

* Atrial flutter
* Ventricular flutter
* Atrial fibrillation
* Familial
* Ventricular fibrillation

Pacemaker|

* Ectopic pacemaker / Ectopic beat
* Multifocal atrial tachycardia
* Pacemaker syndrome
* Parasystole
* Wandering atrial pacemaker

Long QT syndrome|

* Andersen–Tawil
* Jervell and Lange-Nielsen
* Romano–Ward

Cardiac arrest|

* Sudden cardiac death
* Asystole
* Pulseless electrical activity
* Sinoatrial arrest

Other / ungrouped|

* hexaxial reference system
* Right axis deviation
* Left axis deviation
* QT
* Short QT syndrome
* T
* T wave alternans
* ST
* Osborn wave
* ST elevation
* ST depression
* Strain pattern

Cardiomegaly|

* Ventricular hypertrophy
* Left
* Right / Cor pulmonale
* Atrial enlargement
* Left
* Right
* Athletic heart syndrome

Other|

* Cardiac fibrosis
* Heart failure
* Diastolic heart failure
* Cardiac asthma
* Rheumatic fever

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