• Ventricular Electrode
• Localization of the Electrode in the Right Ventricle
• ECG and Pacing from the Right Ventricular Apex
• ECG and Pacing from the Right Ventricular Outflow Tract
• CRT (Cardiac Resynchronization Therapy)
• ECG and Pacing from the Left Ventricle
• ECG and Biventricular Pacing

Ventricular Electrode

• During ventricular pacing, the ventricular electrode can be placed in the:
• Apex of the right ventricle (most common)
• Outflow tract of the right ventricle

ECG and Pacing from the Right Ventricular Apex

• Limb Leads:
• Heart Axis is turned to
• Left Upper Quadrant
• Negative QRS (II, III, aVF)
• Predominantly Positive QRS (I)
• Right Upper Quadrant
• Negative QRS (II, III, aVF)
• Predominantly Negative QRS (I)
  
  
• Precordial Leads
• Show an image of left bundle branch block
• Dominant QRS (V6) and Negative QRS (V1)
• Rarely there is a QS configuration (V1-V6)

ECG and Pacing from the Right Ventricular Outflow Tract

• Limb Leads
• Heart Axis is normally turned to:
• Left Lower Quadrant
• Positive QRS (II, III, aVF)
• Highest QRS (II)
• Precordial Leads
• Show an image of left bundle branch block
• Dominant QRS (V6) and Negative QRS (V1)
• Rarely there is a QS configuration (V1-V6)
  
  
• The electrode can be in 4 parts of the RV outflow tract
• It is not possible to localize which part based on the ECG:
• Lower Septum (LS)
• Upper Septum (US)
• Upper Wall of the Outflow Tract (UOT)
• Lower Wall of the Outflow Tract (LOT)

CRT (Cardiac Resynchronization Therapy)

• CRT is a device for cardiac resynchronization therapy
• It is used for dyssynchronous ventricular contraction
• For example, in left bundle branch block
• When the right ventricle contracts earlier than the left
  
  
• CRT has 3 electrodes:
• Right atrium
• The atrial electrode performs sensing
• Right ventricle (apex)
• Left ventricle (inserted through the coronary sinus)
• The ventricular electrodes perform synchronous biventricular pacing

Ventricular Pacing from the Left Ventricle

• Precordial Leads
• Show an image of right bundle branch block
• Dominant QRS (V1)
• Limb Leads:
• Right Axis Deviation
• Negative QRS (aVL)
• Height of QRS in III > aVF

Biventricular Ventricular Pacing

• Precordial Leads
• Show an image of right bundle branch block
• Dominant QRS (V1)
• Deep S (V6)
• Extreme Right Axis Deviation
• Negative QRS (II, III, aVF)
• Predominantly positive QRS (aVR)
• QRS complexes are relatively narrow
• Because the ventricles are stimulated simultaneously from 2 sites:
• Apex of the right ventricle
• Coronary sinus of the left ventricle
• With pacing only from the right or left ventricle, they would be wider
• Because ventricular activation would take longer