452_Basic EKG by ajizai

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									Basic Electrocardiography
 Electrical = mechanical events
 EKG conventions – language
 Basic interpretation
 Practice strips (lab sessions)
Review
   Action Potentials
      RMP = ~ -90mV

      Depolarization = RMP becomes more positive

   Cardiac Muscle Cell
      Self-generating AP

      Conducted directly from cell to cell

      No twitch contractions

   Heart as a Pump
      Pulmonary vs. systemic

      Aerobic metabolism

      System and pump blood supply

   Conduction System
Purpose of ECG/EKG
 Picture of electrical events
 Established electrode pattern results in
  specific tracing pattern
 Health of heart can be examined using EKG
 Electrical pattern reveals blood supply
  problems
ECG/EKG
 Summation of AP of cardiac cells
 Force vector = direction and magnitude
 12 lead EKG - “Views”
    Bi-polar limb leads - FRONTAL

       I, II & III

       Augmented voltage; aVF, aVL, aVR

    Uni-polar chest leads - TRANSVERSE

       V1 – V6

       Through AV node and “exit” to back
Depolarization and EKG
 Positive/upward vs. negative/downward
  inflection
 “wave of depolarization” = “wave of
  positive charge”
 Wave of depolarization moving towards
  positive electrode = positive inflection
 12 leads – different views of the same
  electrical activity
Electrical = Mechanical activity
 P wave = atrial contraction
 PR segment = allows time for blood to pass
  from atria to ventricles
 QRS
    Shape based on direction/spread of
     depolarization
    Duration

 T wave = ventricular repolarization
    Reverse order of depolarization

 Atrial repolarization during QRS
Depolarization and EKG
   SA node – silent
   Atrial DP – P wave
   AV node – PR interval
   His bundle – PR interval
   Purkinje fibers – PR interval
   Ventricular depolarization – QRS complex
   Ventricular isoelectric period (initial – plateau of
    ventricular repolarization) – ST segment
   Ventricular repolarization – T wave
The Normal EKG
EKG Recording
 Time recorded on X axis (25 mm = 1 sec)
 Voltage recorded on Y axis (10 mm = +1
  mV)
 Smallest divisions are 1 mm by 1 mm
 Heavy black lines = 5 mm square
 Amplitude vs. deflection
 1 mm = 0.04 sec; heavy lines = 0.2 sec
 3 sec marks = bottom/top of paper
Basic EKG – 6 Limb Leads
 Standard & augmented leads
 Divide chest into 30 degree “views”
 “lateral leads” – I & aVL
 “inferior leads” – II, III & aVF
 I = 0 degrees (+), 180 = (-)
 aVF = +90 (+), -90 (-)
Basic EKG Conventions
   Einthoven’s Triangle
     Bipolar limb leads

     Pair of electrodes (positive & negative)

        I (LA+, RA-)

        II (LL+, RA-)

        III (LL+, LA-)

     FRONTAL plane
Basic EKG Conventions
 Augmented Voltage Leads
 One positive limb lead and remaining 2
  leads combine to be negative lead
    aVF (LF+,RA-,LA-)

    aVL (LA+,RA-,LF-)

    aVR (RA+,LA-,LF-)
             Performing an EKG
  1. Standard Limb Leads (right arm, left arm, left leg – actually
     placed on shoulder and hip respectively. Result in a
     triangle formed over the heart (Einthoven’s Triangle).

       Rt. Arm          -   Lead I
                                         +        Lft. Arm
                    -                     -

                 Lead II               Lead III


3 intersecting leads       +     +
                                     Lft. Leg
With 60 degrees between each
Basic EKG – 6 Chest Leads
 Cover heart in normal anatomical position
 Horizontal or TRANSVERSE plane
 V1, V2 = right chest
 V3, V4 = inter-ventricular septum
 V5, V6 = left chest
 Inflection changes from V1 to V6
Performing an EKG

             Chest Leads
             Precordial Leads
EKG Analysis Sequence
 Rate
 Rhythm/Configuration
 Axis
 Hypertrophy
 Infarction


   Funny Looking Beats (FLB) !!
Rate
 Cardiac cycles per minute
 SA node “pacemaker” normal rate of 60-100
  bpm
 Sinus Bradycardia = sinus rhythm < 60 bpm
 Sinus Tachycardia = sinus rhythm > 100 bpm
Rate
   Ectopic foci; automaticity foci pace at inherent rate
    AV node = 60-80 bpm
   Junctional foci = 40-60 bpm
   Ventricular foci = 20-40 bpm
   “Overdrive-suppression”
   Emergency failsafe pacing
   Blocks vs. additional pacing
Rate calculation
   Methods – no calculator
     Triplets; 300, 150, 100, 75, 60, 50

     < 60 bpm; # cycles per 6-sec strip, add 0

   Methods – calculator
     Divide 1500 by # of square between Ps or Rs
      (0.04 sec x 1500 = 60 sec): VARIABLE – not
      good with irregular rhythms
     Measure mm between several complexes;
      divide (1500/mm)*cycles: SUMMARY -
      better
Rhythm
   P and R rates match?
   1 P for each QRS?
   Waves look similar?
   Check P-R interval
      Count from beginning of P to start of R

      Normal = 0.12 – 0.20 sec

   Check QRS interval
      Check limb leads; Q to end of S

      Bundle branch block = > 0.12 sec
Irregular Rhythms
 Wandering Pacemaker
 Multifocal Atrial Tachycardia
 Atrial Fibrillation
Premature Beats
 Premature Atrial Contraction (PAC)
    Irregular p rhythm

 Premature ventricular contraction (PVC)
    Great width and height/depth

    Ventricles are not completely filled

    Compensatory pause

    Uni-focal vs. multi-focal
Tachy-Arrhythmias
 Flutter = 250-350 bpm
 Atrial – identical P waves “saw teeth”
 Ventricular – smooth sine-wave pattern
Tachy-Arrhythmias
   Fibrillation – total erratic rhythm caused by many
    different foci
   Atrial
      Wavy baseline with or without P waves

      QRS not regular – fast or slow

   Ventricular
      Total erratic appearance with no identifiable
       waves
      DANGEROUS!
Heart Blocks
 Blocks of electrical conduction prevent or
  delay the passage of depolarization
 Can occur in SA node, AV node or any
  other division
 Usually seen as prolonged time between p
  wave and QRS complex
Axis
   Direction of the movement of depolarization
     Vector – indicates direction and magnitude

     Mean QRS Vector = summation of small vector
       direction and magnitude
     AV Node is center

   Clinical Importance:
     Hypertrophy; points TOWARD

     Infarction; points AWAY
Axis con’t
 Normal axis = 0 to +90 degrees
 Analyze quadrant with Lead I and aVF
   Two thumbs up = POSITIVE
Rotation
 Chest leads – horizontal plane
 V2: front +, back –
 QRS transition from V2 to V6 (transitional
  zone = V3 or V4)
 Location of transitional zone or “isoelectric
  QRS” determines the direction of rotation
 TOWARD Ventricular hypertrophy and
  AWAY from infarction
Hypertrophy
   Left ventricular hypertrophy – LVH
     Exaggerated amplitude (height and depth)

     V1 – very deep S in V1

     V5 – very tall R wave

     Diagnosis = V1 (S) + V5 (R ) > 35 mm
Classic Triad of MI
    Ischemia
       Reduced blood supply

       Inverted symmetrical T waves OR ST segment
        depression
       Check chest leads!

    Injury (acute or recent infarct)
       ST segment elevation

       Earliest EKG sign of an infarct

    Infarction
       Presence of Q wave

       1 mm wide or 1/3 QRS complex

								
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