![]() ![]() The following figure shows pathological Q-waves in two patients with acute STEMI. *QS complex implies that the entire QRS complex is comprised of one negative deflection. Lead III may also display small Q-waves (not related to respiration) in individuals with electrical axis -30° to 0°. There are limited data regarding the association of Q-wave regression and clinical outcomes. Moreover, fragmented QRS is associated with an increased risk. Background: Pathological Q waves are correlated with infarct size, and Q-wave regression is associated with left ventricular ejection fraction improvement. The absence of fragmented QRS has a high negative predictive value (93) for myocardial infarction. However, the specificity was lower for fragmented QRS (89 vs 99). Lead III occasionally displays a large isolated Q-wave this is called a respiratory Q-wave, because its amplitude varies with respiration. The sensitivity of fragmented QRS for myocardial infarction was 86, as compared with 36 for pathological Q-waves. An isolated QS complex is allowed in lead V1 (due to missing r-wave or misplaced electrode). Leads V5–V6 often display a small q-wave (called septal q-wave, explained in this article). Abnormal Q waves are one of the most common ECG abnormalities in HCM, occurring in 20 to 50 of patients, and occur most frequently in young patients with HCM.5. Individuals with electrical axis 60–90° often display a small q-wave in aVL. Conclusions: This ECG pattern is a sign of prior myocardial infarction in only a minority of cases, and in the latter, infarction limited to the interventricular septum. ECG criteria for pathological Q-waves (Q-wave infarction) Lead Neither the intermittence of Q wave in V2 on repeated ECGs nor the absence of septal Q waves was useful in distinguishing between those with and without coronary heart disease. In patients with STEMI, ST-segment elevations and pathological Q-waves occur in the same leads, which is why pathological Q-waves can be used to localize the infarct area. Hence, Q-wave infarctions are mostly the result of transmural infarction (STEMI) but may be caused by extensive subendocardial ischemia ( NSTEMI).Įstablishing a diagnosis of Q-wave infarction requires that pathological Q-waves be present in at least two anatomically contiguous leads. If pathological Q-waves occur as a result of myocardial infarction, the infarction may be classified as Q-wave infarction (this has negligible clinical implication). Moreover, magnetic resonance imaging has suggested that pathological Q-waves may also arise due to extensive subendocardial infarction (NSTEMI). The amplitude of Q-waves may also diminish over time. Pathological Q-waves may resolve in up to 30% of patients with inferior infarction. However, recent studies challenge these notions. These Q-waves are wider and deeper than normally occurring Q-waves, and they are referred to as pathological Q-waves. They typically emerge between 6 and 16 hours after symptom onset, but may occasionally develop earlier. Standard textbooks have traditionally taught that the pathological Q-wave is a permanent ECG manifestation and that it represents transmural infarction (STEMI). Myocardial infarction – particularly if extensive in size – typically manifests with pathological Q-waves. Pathological Q-waves are evidence of myocardial infarction ![]()
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