Significant if >1 box wide or if is 1/3 of entire QRS amplitude
Early Repolarization:
ST Elevation most prominent in lateral precordial leads (V4-6)
Lack of reciprocal changes helps to differentiate from STEMI
T waves usually broad, tall (>5mm) & upright
Limb leads may also have ST elevation, rarely >2 mm
ST Elevation most prominent in lateral precordial leads (V4-6)
Lack of reciprocal changes helps to differentiate from STEMI
T waves usually broad, tall (>5mm) & upright
Limb leads may also have ST elevation, rarely >2 mm
Lack of reciprocal changes helps to differentiate from STEMI
Q waves do not always indicate infarction
Must distinguish normal septal q waves from<unk> :
Normal septal q wave: <0.04s, low amplitude
Abnormal septal q wave: >0.04s in I OR in II, III, AND aVF OR V3, V4, V5, AND V6
Q-wave equivalents in the precordial leads:
R-wave diminution or poor R-wave progression
Reverse R-wave progression (R waves increase then decrease in amplitude)
Must distinguish from lead misplacement
Tall R waves in V1, V2 (representing "Q waves" from posterior infarction)
Normal septal q wave: <0.04s, low amplitude
Abnormal septal q wave: >0.04s in I OR in II, III, AND aVF OR V3, V4, V5, AND V6
R-wave diminution or poor R-wave progression
Reverse R-wave progression (R waves increase then decrease in amplitude)
Must distinguish from lead misplacement
Tall R waves in V1, V2 (representing "Q waves" from posterior infarction)
Must distinguish from lead misplacement
Pathologic Q waves
Pathologic Q waves 
Wide-complex tachycardia
LBBB
Narrow-complex tachycardia
LVH
Low ECG voltage
Chronic lung disease