Published in:
01-08-2021 | Electrocardiography | Editorial
Myocardial infarction assessment by surface electrocardiography
Authors:
Haren Patel, MD, Harish Doppalapudi, MD, Fadi G. Hage, MD, MASNC
Published in:
Journal of Nuclear Cardiology
|
Issue 4/2021
Login to get access
Excerpt
Surface electrocardiography (ECG) is often used clinically for the detection of myocardial infarction (MI). Although prior guidelines used to classify MI as Q-wave and non-Q-wave MIs, current guidelines rely on ST segment shift on the ECG to differentiate ST-elevation MI from non-ST elevation acute coronary syndrome since that has direct impact on clinical management
1. Further, we now realize that transmural MI may occur without Q waves on the ECG and non-transmural MIs may be accompanied by Q waves
2. Nevertheless, the presence of Q waves on an ECG is helpful to suggest the presence of prior MI. In this regards, not all Q waves on ECG tracings are pathologic; pathologic Q waves are defined in the Fourth Universal Definition of Myocardial Infarction as the presence of Q wave in leads V2-V3 > 0.02 s or QS complex in leads V2-V3; Q wave ≥ 0.03 s and ≥ 1 mm deep or QS complex in leads I, II, aVL, aVF, or V4-V6 in any 2 leads of a contiguous lead grouping (I, aVL; V3-V6; II, III, aVF); or an R wave > 0.04 s in V1-V2 and R/S > 1 with a concordant positive T wave in absence of conduction defect
3. Even pathologic Q waves may be present in the absence of MI. Notoriously, lead misplacement can result in the misdiagnosis of MI by ECG. Any condition that induces a shift in the position of the heart in relation to the surface ECG leads can have similar consequences. Other conditions that have been associated with Q waves in the absence of MI include Wolff-Parkinson-White syndrome, amyloid heart disease, hypertrophic cardiomyopathy, non-ischemic dilated cardiomyopathy, chronic obstructive pulmonary disease, left bundle branch block, and paced rhythm
2. …