Are Q waves present with STEMI?
Data from clinical trial databases of patients with STEMI have shown that the presence of Q waves is associated with adverse cardiovascular outcomes, including higher mortality.
What do Q waves indicate?
Technically, a Q wave indicates that the net direction of early ventricular depolarization (QRS) electrical forces projects toward the negative pole of the lead axis in question. Although prominent Q waves are a characteristic finding in myocardial infarction, they can also be seen in a number of noninfarct settings.
What happens to Q wave in MI?
This is part of: Myocardial Infarction 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.
When do Q waves appear after MI?
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.
What are normal Q waves?
Normal septal q waves are characteristically narrow and of low amplitude. As a rule, septal q waves are less than 0.04 sec in duration. A Q wave is generally abnormal if its duration is 0.04 sec or more in lead I, all three inferior leads (II, III, aVF), or leads V3 to V6.
What happens during Q wave?
This is known as a Q wave and represents depolarisation in the septum. Whilst the electrical stimulus passes through the bundle of His, and before it separates down the two bundle branches, it starts to depolarise the septum from left to right.
What is the significance of the Q wave in myocardial infarction?
Significance of the Q wave in acute myocardial infarction Acute myocardial infarction may be associated with the development of Q waves on the electrocardiogram (ECG), or with changes limited to the ST segment or T wave. The ECG changes do not accurately differentiate transmural from nontransmural infarction.
What are the ECG criteria for Pathological Q-waves (Q-wave infarction)?
ECG criteria for pathological Q-waves (Q-wave infarction) Lead Definition of pathological Q-wave Normal variants V2–V3 ≥0,02 s or QS complex* None All other leads ≥0,03 s and ≥1 mm deep (or QS complex) Individuals with electrical axis 60–90°
Can R-waves be used to diagnose previous myocardial infarction?
Note that these patients presented with pathological Q-waves, which means that these ECGs were recorded several hours after symptom onset or those are signs of old infarction. Current European (ESC) guidelines suggest that R-waves may also be used to diagnose previous myocardial infarction.
Why does posterior MI produce Q waves?
Posterior MI doesn’t produce Q-waves on the 12 lead (unless associated with inferior or lateral MI), but instead produces tall R waves in the anterior leads. Secondary to abnormal depolarization (reversed septal depolarization in LBBB, abnormal conduction in LVH, accessory pathway in WPW)