Updated: 4/5/2018

Electrocardiogram (ECG)

Topic
Review Topic
0
0
Questions
2
0
0
Videos
1
https://upload.medbullets.com/topic/108017/images/080817vldcardiacheartexcitation.jpg
https://upload.medbullets.com/topic/108017/images/04042018mdstep1ecgecganatomy.jpg
https://upload.medbullets.com/topic/108017/images/04032018mdstep1cardslimbleadsupdated.jpg
https://upload.medbullets.com/topic/108017/images/04042018mdstep1ecgdeflectionleadi.jpg
https://upload.medbullets.com/topic/108017/images/04042018mdstep1ecgprecordialleadsupdated.jpg
Introduction
  • The electrocardiogram (ECG) records the flow of electrical impulses throughout the heart
  • Electrical currents flow from negatively charged areas to positively charged areas
    • depolarization currents flowing towards a positive electrode will lead to an upward deflection seen in the ECG reading 
    • repolarization currents flowing away from the positive electrode will lead to a downward deflection seen in the ECG reading 
    • the ECG records the sum of the electrical forces that flow through the heart
      • the ECG deflections depend on how these electrical forces align to a specific ECG lead 
        • e.g., lead aVR, a right-arm electrode, will demonstrate a positive deflection when electrical activity points towards the right arm 
C1: Snapshot: Y
C2: Content/grammar: Y
C3: Images/Videos: N
C4: Questions: Y
C5: References: N
ECG Lead Reference
  • There are 6 limb leads and 6 chest lead, which comprise the 12-lead ECG 
    • limb leads 
      • aVR, aVL, and aVF
      • I, II, III
      • the limb leads read electrical forces in the frontal view
    • chest (precordial) leads 
      • V1-V6
      • the precordial leads read electrical forces in the perpendicular plane
Conduction Pathway
  • Depolarization normally begins at the sinoatrial (SA) node 
    • the SA node is located at the junction of the superior vena cava and right atrium
  • Depolarization from the SA node spreads to the right and left atria
  • After the right and left atria, the wave of depolarization reaches the atrioventricular (AV) node
    • there is an expected delay in the transmission of depolarization to the ventricles at the AV node
  • The impulse then goes to the bundle of His and then the right and left Purkinje fibers
  • Pacemaker rates
    • SA > AV > bundle of His/Purkinje/ventricles
  • Speed of transmission
    • bundle of His = Purkinje fibers > atria > ventricles > AV node
ECG And Conduction Pathway 
 
ECG Basics
ECG Finding
Information
P wave
  • Represents atrial depolarization
PR interval
  • Represents the time from the start of atrial depolarization to the start of ventricular depolarization
  • Normally < 200 msec
QRS complex
  • Represents ventricular depolarization
  • Normally < 120 msec
ST segment
  • Represents an isoelectric point in ventricular depolarization
  • Correlates with phase 2 (plateau) of ventricular action potential 
T wave 
  • Represents ventricular repolarization
  • Becomes peaked in hyperkalemia and flattened in hypokalemia
U wave
  • Believed to represent ventricular repolarization but during the late phase
  • Becomes prominent in hypokalemia
J point
  • The point between the end of the QRS complex and the beginning of the ST segment
 
 

Please rate topic.

Average 5.0 of 7 Ratings

Thank you for rating! Please vote below and help us build the most advanced adaptive learning platform in medicine

The complexity of this topic is appropriate for?
How important is this topic for board examinations?
How important is this topic for clinical practice?
Questions (2)
Lab Values
Blood, Plasma, Serum Reference Range
ALT 8-20 U/L
Amylase, serum 25-125 U/L
AST 8-20 U/L
Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca2+) 8.4-10.2 mg/dL
Cholesterol, serum Rec: < 200 mg/dL
Cortisol, serum 0800 h: 5-23 μg/dL //1600 h:
3-15 μg/dL
2000 h: ≤ 50% of 0800 h
Creatine kinase, serum Male: 25-90 U/L
Female: 10-70 U/L
Creatinine, serum 0.6-1.2 mg/dL
Electrolytes, serum  
Sodium (Na+) 136-145 mEq/L
Chloride (Cl-) 95-105 mEq/L
Potassium (K+) 3.5-5.0 mEq/L
Bicarbonate (HCO3-) 22-28 mEq/L
Magnesium (Mg2+) 1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)  
24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL
Ferritin, serum Male: 15-200 ng/mL
Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL
Female: premenopause: 4-30 mIU/mL
midcycle peak: 10-90 mIU/mL
postmenopause: 40-250
pH 7.35-7.45
PCO2 33-45 mmHg
PO2 75-105 mmHg
Glucose, serum Fasting: 70-110 mg/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative stimuli: > 7ng/mL
Immunoglobulins, serum  
IgA 76-390 mg/dL
IgE 0-380 IU/mL
IgG 650-1500 mg/dL
IgM 40-345 mg/dL
Iron 50-170 μg/dL
Lactate dehydrogenase, serum 45-90 U/L
Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL
Female: follicular phase: 5-30 mIU/mL
midcycle: 75-150 mIU/mL
postmenopause 30-200 mIU/mL
Osmolality, serum 275-295 mOsmol/kd H2O
Parathyroid hormone, serume, N-terminal 230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L
Phosphorus (inorganic), serum 3.0-4.5 mg/dL
Prolactin, serum (hPRL) < 20 ng/mL
Proteins, serum  
Total (recumbent) 6.0-7.8 g/dL
Albumin 3.5-5.5 g/dL
Globulin 2.3-3.5 g/dL
Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL
Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h
Thyroxine (T4), serum 5-12 μg/dL
Triglycerides, serum 35-160 mg/dL
Triiodothyronine (T3), serum (RIA) 115-190 ng/dL
Triiodothyronine (T3) resin uptake 25%-35%
Urea nitrogen, serum 7-18 mg/dL
Uric acid, serum 3.0-8.2 mg/dL
Hematologic Reference Range
Bleeding time 2-7 minutes
Erythrocyte count Male: 4.3-5.9 million/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 12.0-16.0 g/dL
Hemoglobin, plasma 1-4 mg/dL
Leukocyte count and differential  
Leukocyte count 4,500-11,000/mm3
Segmented neutrophils 54%-62%
Bands 3%-5%
Eosinophils 1%-3%
Basophils 0%-0.75%
Lymphocytes 25%-33%
Monocytes 3%-7%
Mean corpuscular hemoglobin 25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration 31%-36% Hb/cell
Mean corpuscular volume 80-100 μm3
Partial thromboplastin time (activated) 25-40 seconds
Platelet count 150,000-400,000/mm3
Prothrombin time 11-15 seconds
Reticulocyte count 0.5%-1.5% of red cells
Thrombin time < 2 seconds deviation from control
Volume  
Plasma Male: 25-43 mL/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 19-31 mL/kg
Cerebrospinal Fluid Reference Range
Cell count 0-5/mm3
Chloride 118-132 mEq/L
Gamma globulin 3%-12% total proteins
Glucose 40-70 mg/dL
Pressure 70-180 mm H2O
Proteins, total < 40 mg/dL
Sweat Reference Range
Chloride 0-35 mmol/L
Urine  
Calcium 100-300 mg/24 h
Chloride Varies with intake
Creatinine clearance Male: 97-137 mL/min
Female: 88-128 mL/min
Estriol, total (in pregnancy)  
30 wks 6-18 mg/24 h
35 wks 9-28 mg/24 h
40 wks 13-42 mg/24 h
17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 6-15 mg/24 h
Osmolality 50-1400 mOsmol/kg H2O
Oxalate 8-40 μg/mL
Potassium Varies with diet
Proteins, total < 150 mg/24 h
Sodium Varies with diet
Uric acid Varies with diet
Body Mass Index (BMI) Adult: 19-25 kg/m2
Calculator

Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK
Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK
VIDEOS (1)
Topic COMMENTS (9)
Private Note