Yu Yan – MI Findings on Investigations – FINAL.pptx
Myocardial Infarction: Findings on InvestigationsAuthor: Yan YuReviewers:Sean SpenceTristan JonesNanette Alvarez** MD at time of publicationTissue ischemia disrupts normal cardiac electrical conduction(detected on serial ECG)Acute, trans-mural myocardial ischemiaIschemia of sub-endocardial myocardiumMyocardial infarctionNote: Both types of ST-segment changes are non-specific: they can indicate Myocardial Infarctions , but can also be false positives (i.e. caused by left ventricular hypertrophy, bundle branch blocks, and other non-myocardial ischemic causes)If ischemia progresses to tissue infarctionPathologic Q-waves (localizes to site of ischemia)Tissue necrosis ? Local myocardial inflammation2-4 hours after MI: troponin proteins released into blood3-8 hours after MI:Creatinine-kinase MB-isozymes released into blood? serum Cardiac Troponins: cTnT, cTnI(Sensitive and most specific serum marker for myocardial necrosis)Relatively faster clearance from circulation? serum CK-MB(less sensitive and specific for myocardial necrosis than Troponins)ST-segment depression(non-localizing)Inflammatory cytokines can spread systemicallyStimulation of neutrophil and monocyte migration towards area of inflammation? WBC count (on CBC)? C-Reactive Protein (CRP)Dead, damaged cardiac myocytes release inner contents into the bloodRelatively slower clearance from circulationSerum CK-MB levels normalize within 3 daysSerum Troponin levels normalize within 14 daysNote: Measuring both CK-MB and Troponins gives a timeline to the MI. For instance, if CK-MB is normal but Troponins are high, it means the MI happened >3 days but <14 days ago.ST-segment elevation(localizes to site of ischemia)Legend:Published January 30, 2013 on www.thecalgaryguide.comMechanismPathophysiologySign/Symptom/Lab FindingComplications 104 kB / 212 words