Pathologic Q Waves: Difference between revisions

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{{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]]'''. The 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'''. One 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'''.
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>Alpert</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>


;Definition of a pathologic Q wave
;Definition of a pathologic Q wave
:Any Q wave in leads V1-V3
:Any Q-wave in leads V2–V3 ≥ 0.02 s or QS complex in leads V2 and V3
:Q wave > or = to 30ms (0.03s) in leads I, II, aVL, aVF, V4, V4, or V6 (the Q wave changes must be present in any two contiguous lead, and be > or = 1mm in depth).
:Q-wave ≥ 0.03 s and > 0.1 mV deep or QS complex in leads I, II, aVL, aVF, or V4–V6 in any two leads of a contiguous lead grouping (I, aVL,V6; V4–V6; II, III, and aVF)
:R-wave ≥ 0.04 s in V1–V2 and R/S ≥ 1 with a concordant positive T-wave in the absence of a conduction defect


'''Notes'''
'''Notes'''
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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}}
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==Referenties==
==References==
<biblio>
<biblio>
#Alpert pmid=10987628
#Alpert pmid=10987628
#Thygesen pmid=17951284
#novacode pmid=9682893
</biblio>
</biblio>

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