ECG NOMENCLATURE

• An ECG provides a visual representation of the spread of electrical events through the heart. This electrical activity is detected on the surface of the body using recording electrodes. 
• 'Leads’ consisting of a pair of electrodes (one positive and one negative) are used to record the electrical activity.
• P wave

  • Signifies Atrial Depolarization (positive charge = atrium/atrial cells)
• DEPOLARIZATION precedes SYSTOLE the same way as REPOLARIZATION precedes DIASTOLE 

  • it does not happen simultaneously
• QRS Complex

  • Signifies: Atrial Repolarization (negatively charge = atrial cells  = relax) and Ventricular Depolarization (positive charge = ventricular cells = contraction of ventricles)
• Ventricle and Atrium cannot contract at the same time because there will be no passage of blood
• T wave

  • Ventricular Repolarizationn

  (negatively charge = ventricular cells = relax)
• Wigger's Diagram

  • P-wave

  Atrial Depolarization to Contraction (Atrial Systole) = increase Atrial Pressure
• 1. QRS Complex 

  • Atrial Repolarization

  1. = Relax (Atrial Diastole) = Lower Atrial Pressure

  • Mitral valve closes = 1st heart sound (closure of atrioventricular valves)
  • also applicable on right side of the heart

  *Remember: Atrial Repolarization =  Closing of Atrioventricular valve

  • Ventricular Depolarization = Contraction (Ventricular Systole) = increase Ventricular Pressure
• If heart contracts = increase in ventricular pressure = volume of blood inside ventricles are pumped outside = ventricular volume decrease

  Remember: Heart contraction (Systole) = Decrease in Ventricular Volume
• T wave

  1. Ventricular Repolarization = Relax (Ventricular Diastole) = Ventricular Pressure Decrease = Mitral Valve open

  *Mitral Valve open = Aortic Valve close = 2nd Heart Sound
• • Ventricular Repolarization: This is associated with the closing of the semilunar valves.
  • Valves during the cardiac cycle
  • When atrioventricular valves are open, the semilunar valves are closed.
  • Relaxation (Diastole):
  • During diastole, the ventricles relax and blood fills the chambers (increased blood volume).
  • Despite the increased volume, ventricular pressure remains low because the ventricles are relaxed.