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Myocardial Infarction: Difference between revisions
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|mainauthor= [[user:Vdbilt|I.A.C. van der Bilt, MD]] | |mainauthor= [[user:Vdbilt|I.A.C. van der Bilt, MD]] | ||
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Ischemia occurs when part of the heartmuscle, the myocardium, is deprived form oxygen and nutrients. | Ischemia occurs when part of the heartmuscle, the myocardium, is deprived form oxygen and nutrients. | ||
Common causes of ischemia are: | Common causes of ischemia are: | ||
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* Shock (manifesting as paleness, low blood pressure, fast weak pulse) shock | * Shock (manifesting as paleness, low blood pressure, fast weak pulse) shock | ||
* Rhythm dysturbances (in particular increasing prevalnce of ventricular ectopia, ventricular tachycardia, AV block) | * Rhythm dysturbances (in particular increasing prevalnce of ventricular ectopia, ventricular tachycardia, AV block) | ||
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===Risk assessment of Cardiovascular disease=== | ===Risk assessment of Cardiovascular disease=== | ||
The narrowing of the coronary artery leading to a myocardial infarction, usually develops over several years. An increased risk of cardiovascular disease, which may lead to a myocardial infarction or stroke, can be estimated using [http://www.escardio.org/initiatives/prevention/prevention-tools/SCORE-Risk-Charts.htm SCORE system] which is developed by the European Society of cardiology (ESC). | The narrowing of the coronary artery leading to a myocardial infarction, usually develops over several years. An increased risk of cardiovascular disease, which may lead to a myocardial infarction or stroke, can be estimated using [http://www.escardio.org/initiatives/prevention/prevention-tools/SCORE-Risk-Charts.htm SCORE system] which is developed by the European Society of cardiology (ESC). | ||
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==Diagnosis of myocardial infarction== | ==Diagnosis of myocardial infarction== | ||
[[Image:Stelevatie_en.png|thumb|ST elevation is measured 60ms or 80ms after the J point]] | [[Image:Stelevatie_en.png|thumb|300px|ST elevation is measured 60ms or 80ms after the J point]] | ||
The diagnosis of acute myocardial infarction is not only based on the ECG. A myocardial infarction is defined as:<cite>Alpert</cite> | The diagnosis of acute myocardial infarction is not only based on the ECG. A myocardial infarction is defined as:<cite>Alpert</cite> | ||
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==The location of the infarct== | ==The location of the infarct== | ||
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Image:coronary_anatomy.png| An overview of the coronary arteries. LM = 'Left Main' = mainstem; LAD = 'Left Anterior Descending' artery; RCX = Ramus Circumflexus; RCA = 'Right Coronary Artery'. | |||
Image:lead_overview.png|Overview of the seperate ECG leads. The lead with ST elevation 'highlights' the infarct. An infarction of the inferior wall will result in ST elevation in leads II, III and AVF. A lateral wall infarct results in ST elevation in leads I and AVL. An Anterior wall infarct results in ST-elevation in the precordial leads. | |||
Image:MI_colours_en.png|The coloured figure shows contiguous leads in matching colours | |||
Image:MIregions.jpg|The ST elevation points at the infarct location. Inferior MI = ST elevation in red regions (lead II,III and AVF). Lateral MI = ST elevation in blue leads (lead I, AVL, V5-V6). Anterio MI: ST elevation in yellow region (V1-V4). Left main stenosis: ST elevation in gray area (AVR) | |||
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The heartmuscle itself is very limited in its capacity to extract oxygen in the blood that is being pumped. Only the inner layers (the endocardium) profit from this oxygenrich blood. The outer layers of the heart (the epicardium) are dependent on the coronary arteries for the supply of oxygen and nutrients. With aid of an ECG, the occluded coronary can be identified. This is valuable information for the clinician, because treatment and complications of for instance an '''anterior wall infarction''' is different than those of an '''inferior wall infarction'''. The anterior wall performs the main pump function, and decay of the function of this wall will lead to decrease of bloodpressure, increase of heartrate, shock and on a longer term: heart failure. An inferior wall infarction is often accompanied with a decrease in heartrate because of involvement of the sinusnode. Longterm effects of an inferior wall infarction are usually less severe than those of an anterior wall infarction. | The heartmuscle itself is very limited in its capacity to extract oxygen in the blood that is being pumped. Only the inner layers (the endocardium) profit from this oxygenrich blood. The outer layers of the heart (the epicardium) are dependent on the coronary arteries for the supply of oxygen and nutrients. With aid of an ECG, the occluded coronary can be identified. This is valuable information for the clinician, because treatment and complications of for instance an '''anterior wall infarction''' is different than those of an '''inferior wall infarction'''. The anterior wall performs the main pump function, and decay of the function of this wall will lead to decrease of bloodpressure, increase of heartrate, shock and on a longer term: heart failure. An inferior wall infarction is often accompanied with a decrease in heartrate because of involvement of the sinusnode. Longterm effects of an inferior wall infarction are usually less severe than those of an anterior wall infarction. | ||
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The localisation of the occlusion can be adequately visualized using a coronary angiogram (CAG). On the CAG report, the place of the occlusion is often graded with a number (for example LAD(7)) using the classification of the American Heart Association.<cite>AHACAG</cite> | The localisation of the occlusion can be adequately visualized using a coronary angiogram (CAG). On the CAG report, the place of the occlusion is often graded with a number (for example LAD(7)) using the classification of the American Heart Association.<cite>AHACAG</cite> | ||
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==Development of the ECG during persistent ischemia== | ==Development of the ECG during persistent ischemia== | ||
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==References== | ==References== | ||
<biblio> | <biblio> | ||
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#Jensen pmid=15851335 | #Jensen pmid=15851335 | ||
</biblio> | </biblio> | ||
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==External Links== | ==External Links== | ||
A good introduction to [http://www.askdrwiki.com/mediawiki/index.php?title=Coronary_Angiography coronary angiography] | A good introduction to [[http://www.askdrwiki.com/mediawiki/index.php?title=Coronary_Angiography coronary angiography]] | ||
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[[Category:ECG Textbook]] | |||