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Can EKG results vary because of EKG lead placement?

I have had ongoing chest pain for about a year and a half. During that time I have had multiple EKG's. Over that time, I have had several different readings. Normal sinus rhythm, enlarged left ventricle (several times), enlarged right atrium, and incomplete bundle branch block. These readings are not consistent from one EKG to another. Can this be due to the EKG itself or lead placement? All troponin results are always good, stress test is good, echocardiogram is good to go. Thank you. 

submitted by John from Fort Lewis, Washington on 8/9/2012


Raymond F. Stainback, MDby Texas Heart Institute cardiologist, Raymond F. Stainback, MD    

Your question is a good one and you already have part of the answer. Everyone has a slightly different heart position within the chest. The leads are placed in "standard" positions on the chest wall that have to do with the location of the ribs as landmarks. This will cause the ECG [electrocardiogram or EKG] recording (and interpretation) to vary if the technician places the leads in a different position from one exam to the next. If the heart lies somewhat away from the standard lead positions, this can give the appearance of pathology even when there is nothing wrong. On the other hand, there are conditions in which the heart actually changes from test to test that could also make the interpretation vary because of valid changes in the ECG signal (not just heart or lead position change). The conduction intervals (incomplete bundle branch block as you mentioned) have to do with the duration of conduction and this would not change with lead position, but it could vary in a patient with exacerbation of lung disease (along with atrial size). There are many variations on this and that is why the ECG cannot be viewed in isolation, but needs to be correlated with signs and symptoms and laboratory values. 

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Updated August 2012
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