The credit for the text referenced through this menu is:Īrgyle, B., MicroEKG Computer Program Manual. You are welcome to use selected portions, as long as appropriate credit is given. Go to Chapter 7, ST and T wave abnormalitiesĪll material referenced through this menu is excerpted from copyrighted works by Bruce Argyle, MD. IHSS: increased septal Qs, evidence of LVH Septal: I, L, V5-V6, occasionally inferior leads 2,3 The overall sensitivity of a Q wave for prior MI is limited by the ECG and is as low as 25 for a lateral MI. 1 However, the Q wave may regress or even disappear over time in as many as 25 to 63 of patients with a history of a Q-wave MI by ECG. These significant Qs of IHSS are almost always accompanied by evidence of marked left ventricular hypertrophy. The presence of pathological Q waves on the 12-lead ECG signifies a prior transmural myocardial infarction (MI). In idiopathic hypertrophic subaortic stenosis (IHSS) the Q waves tend to appear in the same leads in which normal septal Qs are seen because the pathology is thickening of the septum. Created for people with ongoing healthcare needs but benefits everyone. This lack of force has some correlation when a change in pattern with a loss of muscle as is seen in heart damage like a heart attack. A q wave reflects a lack of electrical force in a certain direction. The presence of ST or T wave abnormality in the same lead(s) as borderline Qs makes these Qs suspicious for infarction. EKG : The ekg has waves with amplitude and direction. Q waves that occur in the setting of LBBB or LVH are less reliable for diagnosis of myocardial infarction. Q waves of old infarction in II, III, and F In transmural myocardial infarction, significant Q waves (1 box wide or 1/4 the R) appear in the leads looking at the area of infarction: II, III, and F for inferior infarction I, L, and V5-V6 for lateral and V2-V4 for anterior. Qs in III are ignored unless other abnormalities are seen. Significant Q waves indicate either myocardial infarction or obstructive septal hypertrophy (IHSS).Ī Q wave in lead III alone is not diagnostic of infarction, even if it is otherwise significant in size and width. Q waves are significant if they are greater than 1 box in width (longer than 0.04 msec) OR are larger than 1/4 of the R wave. Small Qs are also generally innocent in lead III and lead V1 if no other abnormality is seen. Septal Qs are normal in I, F, V5 and V6 (left or lateral leads). They will therefore appear in the leads that look left the rightward electrical activity across the septum will cause a negative deflection in these leads. Normal Qs indicate activation of the intraventricular septum. For example in lead I, a Q less than 1/4 of the R height, and less than one box wide, is considered normal. As you read the ECG, you must decide which Q waves indicate pathology, and which Qs are normal. The criteria for abnormal Q waves were defined as follows based on previous studies: (Criterion 1) Q wave >1/3 of the ensuing R wave in depth and/or >0.
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