//fpnotebook.com/
Electrocardiogram
Aka: Electrocardiogram, EKG, ECG
- See Also
- Electrocardiogram in Myocardial Infarction
- Electrocardiogram in Pulmonary Embolism
- Electrocardiogram in Pericarditis
- Electrocardiogram in Atrial Fibrillation
- Background
- Interpretation requires patient age, EKG indication
- Images

- Precautions
- Standard EKG speed and amplitude is nearly always the best setting
- Although EKG gain can be increased and EKG speed can be slowed, the result is often more difficult to interpret
- Do not rely on computerized EKG Interpretation (aside from interval measurement)
- There is no standardization for software quality across EKG manufacturers and accuracy varies widely
- Computer interpretations miss STEMIs in up to 23-41% of cases
- Atrial Fibrillation is a frequent False Positive on computer interpretations
- Pacemaker rhythms are frequently misinterpreted by computers (STEMI False Positives and False Negatives)
- References
- Orman and Mattu in Herbert (2018) EM:Rap 18(3): 1-2
- Schlapfer (2017) J Am Coll Cardiol 70(9): 1183-92 [PubMed]
- Willems (1991) N Engl J Med 325(25):1767-73 +PMID:1834940 [PubMed]
- Components: EKG Paper
- Record speed: 25 mm/sec
- Small square (1 mm): 0.04 seconds
- Large square (5 mm): 0.20 seconds
- Components: Leads
- Limb leads (bipolar)
- Lead I: Left arm - Right arm (0 degrees)
- Lead II: Left leg - Right arm (60 degrees)
- Lead III: Left leg - Left arm (120 degrees)
- Augmented Limb Leads (unipolar)
- Lead aVR: (-150 degrees)
- Lead aVL: (-30 degrees)
- Lead aVF: (90 degrees)
- Precordial Leads (unipolar chest)
- Lead V1: Right sternal border (Right Ventricle)
- Lead V2: Left sternal border
- Lead V3: Medial Breast (Septum)
- Lead V4: Nipple
- Lead V5: Lateral Breast
- Lead V6: Lateral chest wall (Left Ventricle)
- Evaluation: Approach
- Assess EKG Validity
- Rate and Rhythm: "Watch your P's and Q's and the 3R's"
- Lead II P Waves upright? Otherwise not sinus rhythm
- QRS wide or narrow?
- Rate?
- Regularity of Rhythm?
- Relationship between P Waves and QRS Complex
- EKG Axis

- Intervals (prolonged?)
- PR interval
- QRS Complex
- QT Interval
- Hypertrophy?
- Left Ventricular Hypertrophy
- Right Ventricular Hypertrophy
- Right Atrial Enlargement
- Left Atrial Enlargement
- Infarction?
- Q Waves
- R Wave Progression
- ST Segments
- T Waves
- Reference
- Grauer (2001) 12 Lead EKGs, KG/EKG Press, Gainesville
- Interpretation: Specific Circumstances
- See Electrocardiogram in Myocardial Infarction
- See EKG Changes in Syncope due to Arrhythmia
- See Electrocardiogram in Atrial Fibrillation
- See EKG Changes During Pregnancy
- See Hyperkalemia Related EKG Changes
- See Hypokalemia Related EKG Changes
- Ventricular Tachycardia
- Northwest axis (opposite Nl axis)
- V1-V6 positive QRS Complex
- See AV dissociation
- Pericarditis
- See Electrocardiogram in Pericarditis
- Stage I: Diffuse ST inc all leads except aVR, V1
- Stage II: ST segments temporarily normalize
- Stage III: Diffuse ST depress +/- T inversion
- Stage IV: Gradual normalization of ST and T Waves
- Pulmonary Embolism
- See Electrocardiogram in Pulmonary Embolism
- Right Strain Pattern (Classic PE, but rarely seen)
- S1 (deep S wave in lead I)
- Q3 (Q Wave in lead III)
- T3 (inverted T Wave in lead III)
- Atrial Fibrillation or Atrial Flutter with Rapid Ventricular Rate
- See Electrocardiogram in Atrial Fibrillation
- At a rapid rate (e.g. 140-150 bpm), may be difficult to differentiate AFib/Flutter from ST, PSVT
- Increase EKG "paper speed" to 50 mm/sec (rapid) to spread out complexes (P Waves may be seen)
- Mattu (2020) Crit Dec Emerg Med 34(4): 18