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| ==T Wave==
| | #REDIRECT[[ECG (main)]] |
| *Distribution
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| **T wave is normally inverted in aVR; sometimes inverted in III, aVF, aVL, V1
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| *T-wave inversions in V2-V6 are pathologic
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| *Morphology
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| **Inverted, symmetric,
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| **Transient changes suggests ischemia without infarction
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| **Persistent changes suggests infarction (troponin elevation usually seen)
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| *Pseudonormalization
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| **In presence of baseline TWI (within 1 month), reocclusion causes normalization of TWI
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| **Should be interpreted as evidence of ischemia
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| ==Q Wave==
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| *Q waves do not always indicate infarction (see DDX below)
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| *Must distinguish normal septal q waves from pathologic Q waves:
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| **Normal septal q wave: <0.04s, low amplitude
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| **Abnormal septal q wave: >0.04s in I OR in II, III, AND aVF OR V3, V4, V5, AND V6
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| *Q-wave equivalents in the precordial leads:
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| **R-wave diminution or poor R-wave progression
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| **Reverse R-wave progression (R waves increase then decrease in amplitude)
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| ***Must distinguish from lead misplacement
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| **Tall R waves in V1, V2 (representing "Q waves" from posterior infarction)
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| ===Q Wave (Pathologic) DDX===
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| *Ischemic Q waves
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| *LBBB
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| *LVH
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| *Chronic lung disease
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| *Hypertrophic cardiomyopathy
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| *Dilated cardiomyopathy
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| ==ST Segment Depression==
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| *Assume posterior STEMI or reciprocal changes to STEMI until proven otherwise
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| *Indicators of ischemia:
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| **>0.5mm depression from baseline (especially >1mm) in two or more contiguous leads
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| **Transient depression
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| **Morphology that is flat or downsloping
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| ==ST Segment Elevation==
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| *Stage 1
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| **Timing: 30min - hours
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| **Finding: hyperacute T waves
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| ***>6mm limb leads
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| ***>10mm precordial leads
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| **Duration: normalizes in days, weeks, or months
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| *Stage 2
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| **Timing: minutes - hours
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| **Finding: ST segment elevation
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| ***≥0.1mV in two or more contiguous leads
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| **Duration: ST segment resolution occurs over 72hrs; completely resolves w/in 2-3wks
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| *Stage 3
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| **Timing: within 1hr; completed within 8-12hr
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| **Finding: Q waves
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| **Duration: persist indefinitely in 70% of cases
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| ==Reciprocal Changes==
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| #Anterior STEMI | |
| ##Reciprocal ST-segment depression in at least one of leads II, III, aVF
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| ##Occurs in 40-70% of cases
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| #Inferior STEMI
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| ##Reciprocal ST-segment depression usually present in I, aVL; often in V1-V3
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| ##Occurs in 56% of cases
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| #Posterior STEMI
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| ##Reciprocal ST-segment depression in V1-V4
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| ###Differentiate from inf STEMI reciprocal depression based on upright T waves, posterior leads showing STEMI
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| ##Often associated w/ ST-segment elevation in II, III, aVF (inferior involvement)
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| ==See Also==
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| *[[ACS - Anatomical Correlation]]
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| ==Source==
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| *Electrocardiography in Emergency Medicine. ACEP Textbook.
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| [[Category:Cards]]
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