Difference between revisions of "Pathologic Q Waves"

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Revision as of 23:59, 27 April 2008

This is part of: Myocardial Infarction
A pathologic Q wave

Pathologic Q waves are a sign of previous 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. 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.[1]

Definition of a pathologic Q wave
  • Any Q wave in leads V1-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).

Notes

  • Absence of pathologic Q waves does not exclude a myocardial infarction!
  • Lead III often shows Q waves, which are not pathologic as long as Q waves are absent in leads II and aVF (the contiguous leads)

For those interested: the Minnesota Code Classification System for Electrocardiographic Findings contains a very extensive definition of pathologic Q waves.


References

  1. Alpert JS, Thygesen K, Antman E, and Bassand JP. Myocardial infarction redefined--a consensus document of The Joint European Society of Cardiology/American College of Cardiology Committee for the redefinition of myocardial infarction. J Am Coll Cardiol. 2000 Sep;36(3):959-69. DOI:10.1016/s0735-1097(00)00804-4 | PubMed ID:10987628 | HubMed [Alpert]