MEDICINE
CARDIOLOGY
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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generally indicates that an acute myocardial infarction has occurred within the past hour.
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is deeper than one-quarter of the height of the R wave and indicates injury.
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is wider than 0.04 seconds and indicates that a myocardial infarction occurred in the past.
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can only be substantiated by viewing at least two previous 12-lead ECGs.
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Detailed explanation-1: -Pathologic Q waves are a sign of previous 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.
Detailed explanation-2: -Background: Abnormal Q waves (AQW) in the electrocardiogram are commonly ascribed to underlying myocardial infarction (MI). As an imperfectly specific sign of MI, the usefulness of AQW in identifying MI depends on its incidence in the population studied.
Detailed explanation-3: -Q-WAVE ABNORMALITIES They are pathologic if they are abnormally wide (>0.2 second) or abnormally deep (>5 mm). Q waves that are pathologically deep but not wide are often indicators of ventricular hypertrophy. Q waves that are both abnormally deep and wide imply myocardial infarction.
Detailed explanation-4: -Q waves may develop within one to two hours of the onset of symptoms of acute myocardial infarction, though often they take 12 hours and occasionally up to 24 hours to appear. The presence of pathological Q waves, however, does not necessarily indicate a completed infarct.