Difference between revisions of "Myocardial infarction"

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Myocardial infarction (view source)

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#redirect [[Heart#Myocardial infarction]]
{{ Infobox diagnosis
| Name      = {{PAGENAME}}
| Image      = MI_with_contraction_bands_very_high_mag.jpg
| Width      =
| Caption    = Contraction band necrosis - a finding of MI. [[H&E stain]].
| Synonyms  =
| Micro      = wavy fibers, myocyte [[necrosis]] with loss of cross striations, [[contraction band necrosis|contraction bands]], edema, hemorrhage, neutrophilic infiltrate, pyknosis of nuclei, loss of nuclei (karyolysis), loss of striations, macrophage and mononuclear infiltration, fibrovascular response, fibrovascular response, [[granulation tissue]], myocardial fibrosis (old)
| Subtypes  =
| LMDDx      = [[cardiac amyloidosis]] for old infarct, [[myocarditis]]
| Stains    =
| IHC        =
| EM        =
| Molecular  =
| IF        =
| Gross      = myocardial pallor, hyperemia (redness), yellow lesion with hyperemic border, white (fibrosis)
| Grossing  =
| Site      = [[heart]]
| Assdx      = [[coronary artery atherosclerosis]]+/-plaque rupture, +/-thrombosis, cocaine use
| Syndromes  =
| Clinicalhx =
| Signs      = abnormal EKG - esp. ST elevation
| Symptoms  = classic findings: retrosternal chest pain +/- with radiation down the arms, nausea & vomiting, diaphoresis
| Prevalence =
| Bloodwork  = elevated troponin, CK-MB
| Rads      =
| Endoscopy  =
| Prognosis  = dependent on extent
| Other      =
| ClinDDx    = varies by presentation - usu. [[aortic dissection]], [[acute pneumonia]], [[pulmonary embolism]], GI pathology, 
| Tx        =
}}
'''Myocardial infarction''', abbreviated '''MI''', is death of cardiac muscle due to a compromised blood supply. In the context of pathology, they are occasionally seen at [[autopsy]].
 
==General==
===Clinical===
*Usually diagnosed clinically - with blood work (troponin, CK-MB) or EKG.
*MI may be precipitated by cocaine use... and further exacerbated by treatment with a beta-blocker.<ref name=pmid19127137>{{cite journal |author=Mohamad T, Kondur A, Vaitkevicius P, Bachour K, Thatai D, Afonso L |title=Cocaine-induced chest pain and beta-blockade: an inner city experience |journal=Am J Ther |volume=15 |issue=6 |pages=531-5 |year=2008 |pmid=19127137 |doi=10.1097/MJT.0b013e3181758cfc |url=}}</ref>
*Acute myocardial infarction (abbreviated AMI) = MI < 6 hours old.<ref name=pmid19258462>{{Cite journal  | last1 = Senter | first1 = S. | last2 = Francis | first2 = GS. | title = A new, precise definition of acute myocardial infarction. | journal = Cleve Clin J Med | volume = 76 | issue = 3 | pages = 159-66 | month = Mar | year = 2009 | doi = 10.3949/ccjm.75a.08092 | PMID = 19258462 | URL = http://www.ccjm.org/content/76/3/159.full }}</ref>
**Usually no [[PMN]] infiltrate.
 
Classic symptoms:
*Retrosternal chest pain +/- with radiation down the arms.
*Nausea & vomiting.
*Diaphoresis.
 
Enzymatic tests:<ref>URL: [http://pro2services.com/Lectures/Fall/CardEnz/a6mienz.gif http://pro2services.com/Lectures/Fall/CardEnz/a6mienz.gif]. Accessed on: 27 April 2012.</ref>
*CK: peaks at day 1, resolves after 2-3 days.
*AST: peaks close to day 2, resolves after 4-5 days.
*LDH: peaks day 2, resolves after ~6 days.
 
===Complications===
Complications of MI:<ref name=Ref_PCPBoD8_293>{{Ref PCPBoD8|293}}</ref>
*Contractile dysfunction.
*[[Cardiac arrhythmia]].
*Aneurysm formation, e.g. left ventricular aneurysm.
*Ventricular rupture:
**Ventricular free wall rupture.
**Ventricular septal rupture.
*[[Fibrinous pericarditis]].
**''Dressler's syndrome'' [[AKA]] ''postmyocardial infarction syndrome''<ref name=pmid5039567>{{cite journal |author=Hutchcroft BJ |title=Dressler's syndrome |journal=Br Med J |volume=3 |issue=5817 |pages=49 |year=1972 |month=July |pmid=5039567 |pmc=1788531 |doi= |url=}}</ref>; pericarditis post-myocardial infarction +/- pericardial effusion (clinically tamponade).
*Mural thrombosis.
*Extension of MI.
 
==Gross==
Sequence:<ref>[http://library.med.utah.edu/WebPath/TUTORIAL/MYOCARD/MYOCARD.html http://library.med.utah.edu/WebPath/TUTORIAL/MYOCARD/MYOCARD.html]</ref>
*18-24 hours - myocardial pallor.
*1-3 days - pallor, moderate hyperemia (redness due to congestion with blood).
*3-7 days - yellow lesion with hyperemic border.
*10-21 days - maximally yellow.
*6 weeks - white (fibrosis).
 
==Microscopic==
Sequence:<ref>[http://library.med.utah.edu/WebPath/TUTORIAL/MYOCARD/MYOCARD.html http://library.med.utah.edu/WebPath/TUTORIAL/MYOCARD/MYOCARD.html]</ref>
*1-3 hours - Wavy (myocardial) fibers
*4-12 hours - Coagulative [[necrosis]] & loss of cross striations, [[contraction band necrosis|contraction bands]], edema, hemorrhage, PMN infiltrate.
*18-24 hours - Coagulative necrosis, pyknosis of nuclei, and marginal contraction bands.
*1-3 days - Loss of nuclei (karyolysis), loss of striations, abundant PMNs.
*3-7 days - Macrophage and mononuclear infiltration, fibrovascular response.
*10-21 days - Fibrovascular response, prominent granulation tissue.
*6 weeks - Fibrosis.
 
Images:
*[http://path.upmc.edu/cases/case158/micro.html MI (upmc.edu)].
 
===Contraction band necrosis===
General:
*Mediated by catecholamines.<ref>{{cite journal |author=Hopster DJ, Milroy CM, Burns J, Roberts NB |title=Necropsy study of the association between sudden cardiac death, cardiac isoenzymes and contraction band necrosis |journal=J. Clin. Pathol. |volume=49 |issue=5 |pages=403–6 |year=1996 |month=May |pmid=8707956 |pmc=500481 |doi= |url=}}</ref>
*Thought to arise in reperfusion from hypercontraction.
 
Microscopic:
*Thick intensely eosinophilic staining bands (on H&E) ~ typically 4-5 micrometres wide
**Span the short axis of myocyte.
**Can be thought of bunched-up striae.
 
Notes:
*Better seen with special stains (Masson or Gomori trichrome).<ref>{{cite journal |author=Hopster DJ, Milroy CM, Burns J, Roberts NB |title=Necropsy study of the association between sudden cardiac death, cardiac isoenzymes and contraction band necrosis |journal=J. Clin. Pathol. |volume=49 |issue=5 |pages=403–6 |year=1996 |month=May |pmid=8707956 |pmc=500481 |doi= |url=}}</ref>
 
====Images====
<gallery>
Image:MI_with_contraction_bands_high_mag.jpg | CBN - high mag. (WC)
Image:MI_with_contraction_bands_very_high_mag.jpg | CBN - very high mag. (WC)
</gallery>
 
==See also==
*[[Heart]].
 
==References==
{{Reflist|2}}


[[Category:Diagnosis]]
[[Category:Diagnosis]]
[[Category:Heart]]
Michael
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