Basic EKG Interpretation

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Basic EKG Interpretation
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History

• Mid 1880s - Ludwig Waller discovered that the
  hearts rhythm could be monitored from a persons
  skin
• 1901 - Dr. William Einthoven invented the EKG
  machine
• EKG - Electrocardiogram - Electrical activity of
  the heart (contraction of the myocardium)

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Electrical Conduction

• Heart muscle cells - myocytes
• Depolarization moves as a wave through the
  myocardium
• Depolarization stimulates the hearts myocytes,
  they become and contract
• Cell-to-cell depolarization through the
  myocardium is carried with Na ions

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EKG

• Myocardial contraction is caused by
  depolarization. The recovery phase that follows
  depolarization is known as repolarization.
• The SA Node (Sinus Node) is the hearts dominant
  pacemaker. - Sinus Rhythm
• Each depolarization wave emitted through the SA
  Node spreads through the atria producing a P
  Wave.

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• P Wave Atrial Depolarization
• AV Node - Conducting pathway b/t the atria and
  the ventricles
• When a wave of atrial depolarization enters the
  AV Node, depolarization slows, producing a brief
  pause, thus allowing blood to enter the
  ventricles. Ca ions

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Ventricular Conduction

• Depolarization shoots rapidly through the HIS
  Bundle, and the Left Right Bundle Branches
• The HIS Bundle and both Bundle Branches are made
  up of rapidly conducting Purkinje fibers.
• Depolarization of the entire ventricular
  myocardium produces a QRS complex.
• QRS represents ventricular contraction.

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Ventricular Conduction

• The Q Wave, when present, always occurs at the
  beginning of the QRS complex and is the first
  downward deflection.
• The next upward deflection represents the R Wave.
• The next downward wave is the S Wave.
• The horizontal segment of baseline that follows
  the QRS is known as the ST Segment.

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Continued.

• If the ST Segment is elevated or depressed beyond
  baseline level, this is usually a sign of
  problems.
• The ST Segment represents the initial phase of
  Ventricular Repolarization.
• The T Wave represents the final, rapid phase of
  ventricular repolarization.
• The T Wave is usually a low, broad hump.

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• Repolarization is accomplished by K ions leaving
  the myocites.
• Ventricular systole (contraction) begins with the
  QRS and persists until the end of the T Wave.
• Physiologically, a cardiac cycle represents
  atrial contraction, and ventricular contraction
  followed by a resting stage. Page 29

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Recording the EKG

• Page 31
• Smallest divisions are 1 mm high X 1 mm wide.
• 5 small squares make up one large square
• The height or depth of waves is voltage.
• The upward or downward deflection is called
  amplitude.

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EKG Recordings

• The amount of time represented by the distance
  b/t two heavy lines is .2 of a second.
• Each small division represents .04 seconds.
• A standard EKG has 6 limb leads and six chest
  leads.
• Bipolar limb leads - Page 38.

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Limb Leads

• AVR, AVL, AVF are unipolar limb leads.
• Page 42.
• Page 43.
• Page 44.
• 6 Chest Leads
• V1 - V6

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Rate

• R to R intervals
• 300, 150, 100, 75, 60, 50
• 6 second strip
• Count cycles and add a zero to the end

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