Electrocardiography

• History

  • 1786 - Dr. Luigi Galvin
  • 1887 - Augustus D. Waller
  • 1895 - Einthoven
  • 1900 - Willem Einthoven
  • 2018 - Apple smart watch
• Einthoven


  • Date: 1902
  • publishes the first electrocardiogram recorded on a string galvanometer
• Dr. Luigi Galvin

  • Date: 1786
  • first noted that electrical current could be recorded from skeletal muscles
• Augustus D. Waller


  • Date: 1887
  • first “electrogram” (ECG) from the intact human heart was recorded with a mercury capillary electrometer by him at St. Mary’s Hospital London
• Einthoven


  • Date: 1895
  • using an improved electrometer and a correction formula developed independently. He labeled the corrected derived deflections PQRS and T
• Willem Einthoven


  • Date: 1900
  • first article source using the term “Elektrokardiogram” (EKG)
• Einthoven


  • Date: 1902
  • publishes the first electrocardiogram recorded on a string galvanometer
• Apple smart watch


  • Date: 2018
  • over 400,000 people enroll in a study being conducted by researchers at Stanford and Apple to determine whether a wearable technology can identify irregular heart rhythms suggestive of atrial fibrillation
• Electrocardiography 


  measures the heart's electrical activity
• Important Diagnostic too in the evaluation of cardiovascular disease (CVD)

  • Abnormal heart rhythm (arrhythmias)
  • Myocardial ischemia / infarction
  • Chamber enlargement
  • Electrolyte abnormalities
• Purpose of ECG

  • detects the heart’s electrical rhythm and produces what’s known as a tracing
  • tracing consists of representations of several waves that recur with each heartbeat
  • wave pattern should have a consistent shape, if the waves are not consistent or if they don’t appear as standard waves, this is indicative of heart disease
• heart rate

  60-100x per minute
• Cardiac cycle


  • sequence of events, electrical and mechanical events, taking place in the heart from the beginning of one heart beat initiated by an impulse from the SA node to the beginning of the next heat beat also initiated by an impulse from the SA node
• Sinoatrial node


  natural pacemaker of the heart
• 2 types of cardiac cycle

  • Electrical events
  • Mechanical events
• Electrical events

  depolarization and repolarization of the atria ventricle
• Mechanical events


  contraction or relaxation of the atria and ventricles
• ECG SETUP (colors)

  • red - right
  • yellow - left
  • black - right leg
  • green - left leg
• Digital ECG Data Acquisition System

  acquires data from the body and the raw ECG is filter, amplify, and digitized in AFE module
• AFE module

  analogue front end module

  • processor board
• Right leg - black


  • also known as ground electrode
  • removing other electrical potentials aside from the one being produced by the heart
• Types of ECG

  • Resting ECG Tracing
  • Exercise/Stress ECG Tracing
  • Holter Monitor
• Resting ECG Tracing


  • supine without any activity
  • remove accessories in the body
• Exercise/Stress ECG Tracing


  symptoms of difficulty in breathing or chest pain
• Holter Monitor


  • also known as ambulatory ECG
  • attached to the patient for 24 hours
  • complain of palpitations, episodes of sincoves
• ECG Leads

  • Bipolar Limb Leads
  • Unipolar Limb Leads
  • Chest Leads
• Bipolar Limb Leads

  • Lead 1 - right arm and left arm (+)
  • Lead 2 - right arm and left leg (+)
  • Lead 3 - left arm and left leg (+)
• Einthoven’s Triangle Equation

  Lead II = Lead I + Lead III
• Unipolar Limb Leads


  • ECG machine usually augments the potential by 1.5 than the original potential
  • comes from a central terminal
  • Lead aVR (augmented vector right)
  • Lead aVL (augmented vector left)
  • Lead aVF (augmented vector foot)
• Lead augmented vector right

  • towards right arm
  • uppermost right side of the heart
• Lead augmented vector left

  • toward left arm
  • uppermost left side of the heart
• Lead augmented vector foot


  • towards left foot
  • lowermost portion/apex of the heart
• Chest Leads


  • landmark: Angle of Louis
  • represent the horizontal plane of the heart
• Position of the leads

  • V1
  • V2
  • V3
  • V4
  • V5
  • V6
  • Lead V4R
  • Lead V3R
  • V7
  • V8
• V1

  • 4th intercostal space, right parasternal border
  • right ventricle

  
• V2

  • 4th intercostal space, left parasternal border
  • septum

  
• V3

  • located between V2 and V4
  • anterior left ventricle

  
• V4

  • 5th intercostal space, left midclavicular line (usually located below the nipple)
  • Anterior Left ventricle

  
• V5

  • Left anterior axillary line, at the same level as V4
  • Lateral Left Ventricle

  
• V6

  • same level as V4 and V5 but located at the mid axillary line
  • lateral left ventricle