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Pathologic Q Waves: Difference between revisions
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{{Chapter|Myocardial Infarction}} | {{Chapter|Myocardial Infarction}} | ||
[[Image:PathoQ.png|thumb| A pathologic Q wave]] | [[Image:PathoQ.png|thumb| A pathologic Q wave]] | ||
Pathologic Q waves are a sign of '''previous [[Myocardial Infarction|myocardial infarction]]'''. | Pathologic Q waves are a sign of '''previous [[Myocardial Infarction|myocardial infarction]]'''. They are the result of absence of electrical activity. A myocardial infarction can be thought of as an elecrical 'hole' as scar tissue is electrically dead and therefore results in pathologic Q waves. Pathologic Q waves are not an early sign of myocardial infarction, but '''generally take several hours to days to develop'''. Once pathologic Q waves have developed they rarely go away. However, if the myocardial infarction is reperfused early (e.g. as a result of percutaneous coronary intervention) stunned myocardial tissue can recover and pathologic Q waves disappear. In all other situations they '''usually persist indefinitely'''. | ||
The precise criteria for pathologic Q waves have been debated. Here we present the latest definition as accepted by the ESC and ACC.<cite>Thygesen</cite> | The precise criteria for pathologic Q waves have been debated. Here we present the latest definition as accepted by the ESC and ACC.<cite>Thygesen</cite> | ||
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For those interested: the [http://www.epi.umn.edu/ecg/mncode.pdf Minnesota Code Classification System for Electrocardiographic Findings] contains a very extensive definition of pathologic Q waves. | For those interested: the [http://www.epi.umn.edu/ecg/mncode.pdf Minnesota Code Classification System for Electrocardiographic Findings] contains a very extensive definition of pathologic Q waves. | ||
The Novacode system further classifies ischemic abnormalities in patients with no known history of myocardial infarction:<cite>novacode</cite> | |||
* High risk of ischemic injury/ Q wave MI: | |||
** Major Q waves: Q >= 50ms or Q >= 40 ms AND R/Q < 4, | |||
* Moderate risk of ischemc injury / possible Q wave MI: | |||
** Q >= 30 ms and ST deviation > 0.20 mV (minor Q waves with STT abnormalities) | |||
** Q >= 40 ms and ST deviation < 0.20mV (moderate Q waves without STT abnormalities) | |||
* Marginal risk of ischemic injury / possible Q wave MI: | |||
** Isolated T wave abnormalities | |||
** Minor Q waves (shallow Q < 30ms) and ST deviation < 0.15 mV | |||
* Low risk of ischemic injury | |||
** No significant Q waves or STT abnormalities | |||
{{clr}} | {{clr}} | ||
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#Alpert pmid=10987628 | #Alpert pmid=10987628 | ||
#Thygesen pmid=17951284 | #Thygesen pmid=17951284 | ||
#novacode pmid=9682893 | |||
</biblio> | </biblio> | ||