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Transition Zone

Transition zone

Electrical Axis of EKG Leads

Lead axis of the heart

Positive and Negative EKG Deflection

Electrical heart vectors and positive and negative deflection

Biphasic EKG Deflection

Continuously changing resultant voltage vector during heart cycle and ECG deflection
  • Myocardium depolarizes gradually
    • The electrical vector thus rotates around a point
    • e.g., ventricular depolarization
  • EKG lead records the vectors sequentially and generates an EKG curve
    • 1st vector points away from the electrode (+)
    • 2nd vector is perpendicular to the electrode (+)
    • 3rd vector points towards the electrode (+)
    • A biphasic EKG deflection is gradually formed

Precordial Leads

Chest precordial leads, and transition zone V3 - biphasic QRS complex

Cardiac Rotation and Transition Zone

  • Transition Zone
    • Indicates rotation of the heart around the longitudinal axis
    • Similar to rotating your head (right - left)
Heart longitudinal axis rotation in horizontal plane. Transition zone, clockwise and counterclockwise rotation

ECG and Transition Zone

ECG precordial leads, normal R wave progression and transition zone

Transition Zone


Normal Heart Rotation

Transition zone and normal heart rotation in horizontal plane

ECG normal transition zone, R and S wave voltage (R/S = 1) in V3 or V4

Normal Heart Rotation

  • Transition zone is in V3-V4
  • Sometimes considered a normal variant:
    • Early transition zone in V2 (Early transition zone)
    • Delayed transition zone in V5 (Delayed/Late transition zone)

Counterclockwise Heart Rotation

Counterclockwise (CCW) rotation, Early transition zone

Counterclockwise (CCW) rotation, Early transition zone (V1, V2)

ECG precordial leads and Counterclockwise (CCW) rotation, Early transition zone

Counterclockwise Heart Rotation


Clockwise Heart Rotation

Clockwise (CW) rotation, Delayed transition zone, Late transition zone

Clockwise (CW) rotation, Delayed transition zone, Late transition zone

ECG precordial leads and Clockwise (CW) rotation, Delayed transition zone, Late transition zone

Clockwise Heart Rotation



ECG sinus rhythm and normal transition zona V3

Normal Heart Rotation and Sinus Rhythm



ECG arrhythmogenic right ventricular dyplasia and Counterclockwise (CCW) rotation, Early transition zone

Heart Rotation Counterclockwise and Arrhythmogenic Right Ventricular Dysplasia



ECG left ventricular hypertrophy and Clockwise (CW) rotation, Delayed transition zone, Late transition zone

Heart Rotation Clockwise and Left Ventricular Hypertrophy




Sources

  • ECG from Basics to Essentials Step by Step
  • litfl.com
  • ecgwaves.com
  • metealpaslan.com
  • medmastery.com
  • uptodate.com
  • ecgpedia.org
  • wikipedia.org
  • Strong Medicine
  • Understanding Pacemakers





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Transition Zone

Transition zone

Electrical Axis of EKG Leads

Lead axis of the heart



Electrical heart vectors and positive and negative deflection

Positive and Negative EKG Deflection

  • Cardiac Electrical Vector
    • Must always project onto the electrical axis of the EKG lead

  • Positive EKG Deflection occurs
  • Negative EKG Deflection occurs
    • When the vector is directed away from the surface electrode (+)


Continuously changing resultant voltage vector during heart cycle and ECG deflection

Biphasic EKG Deflection

  • Myocardium depolarizes gradually
    • The electrical vector thus rotates around a point
    • e.g., ventricular depolarization
  • EKG lead records the vectors sequentially and generates an EKG curve
    • 1st vector points away from the electrode (+)
    • 2nd vector is perpendicular to the electrode (+)
    • 3rd vector points towards the electrode (+)
    • A biphasic EKG deflection is gradually formed

Precordial Leads

  • Precordial leads (V1-V6)
    • are oriented towards the heart in the horizontal plane

  • Main cardiac vector (VH)
    • Straightest direction is towards lead V6
      • Between the vector and V6 are the lungs (insulator)
    • Dominant R wave is in V5
    • Points away from lead V1
      • where there will be a negative S wave

  • In precordial leads, there is progression of the R wave
    • R wave amplitude increases from lead V1 to V4-5


  • Transition Zone
    • If the main vector (VM) is perpendicular to the chest lead
    • A biphasic QRS complex (R=S) appears in the lead
      • which is referred to as the transition zone
    • The image shows the transition zone in V3

Chest precordial leads, and transition zone V3 - biphasic QRS complex

Cardiac Rotation and Transition Zone

  • Transition Zone
    • Indicates rotation of the heart around the longitudinal axis
    • Similar to rotating your head (right - left)

Heart longitudinal axis rotation in horizontal plane. Transition zone, clockwise and counterclockwise rotation

ECG and Transition Zone

ECG precordial leads, normal R wave progression and transition zone

Transition Zone


Normal Heart Rotation

ECG normal transition zone, R and S wave voltage (R/S = 1) in V3 or V4 Transition zone and normal heart rotation in horizontal plane

Normal Heart Rotation

  • Transition zone is in V3-V4
  • Sometimes considered a normal variant:
    • Early transition zone in V2 (Early transition zone)
    • Delayed transition zone in V5 (Delayed/Late transition zone)

Counterclockwise Heart Rotation

Counterclockwise (CCW) rotation, Early transition zone


ECG precordial leads and Counterclockwise (CCW) rotation, Early transition zone Counterclockwise (CCW) rotation, Early transition zone (V1, V2)

Counterclockwise Heart Rotation


Clockwise Heart Rotation

Clockwise (CW) rotation, Delayed transition zone, Late transition zone


ECG precordial leads and Clockwise (CW) rotation, Delayed transition zone, Late transition zone Clockwise (CW) rotation, Delayed transition zone, Late transition zone

Clockwise Heart Rotation

  • Main cardiac vector rotates toward the left ventricle
    • Clockwise
  • Transition zone is in V5-V6
  • Sometimes considered a normal variant:
    • Delayed transition zone in V5 (Delayed/Late transition zone)


ECG sinus rhythm and normal transition zona V3

Normal Heart Rotation and Sinus Rhythm



ECG arrhythmogenic right ventricular dyplasia and Counterclockwise (CCW) rotation, Early transition zone

Heart Rotation Counterclockwise and Arrhythmogenic Right Ventricular Dysplasia



ECG left ventricular hypertrophy and Clockwise (CW) rotation, Delayed transition zone, Late transition zone

Heart Rotation Clockwise and Left Ventricular Hypertrophy




Sources

  • ECG from Basics to Essentials Step by Step
  • litfl.com
  • ecgwaves.com
  • metealpaslan.com
  • medmastery.com
  • uptodate.com
  • ecgpedia.org
  • wikipedia.org
  • Strong Medicine
  • Understanding Pacemakers