• Precordial Leads and R Wave
• Pathological R Wave
• ECG and Dominant R Wave in V1
• Causes of Dominant R Wave in V1

Precordial Leads and R Wave

• Precordial leads (V1-V6)
• view the heart in the horizontal plane
  
  
• Main Cardiac Vector (V_M)
  • Points most directly towards lead V6
  • There are lungs (insulator) between the vector and V6
  • Dominant R wave is in V5
  • Points away from lead V1
  • where there will be a negative S wave

ECG and Dominant R Wave in V1

• Dominant R in V1
• R wave ≥ S wave

Sinus Tachycardia (2-Year-Old Child)

• 2-Year-Old Healthy Child
• Children have right ventricular hypertrophy from birth
• The right ventricle pumps blood against higher pressure in the womb
• The left ventricle starts to become dominant from the age of 4-6 years
• Sinus Tachycardia at 110/min is physiological in a 2-year-old child
• Dominant R in V1
• It is due to right ventricular hypertrophy
• The hypertrophied right ventricle turns the main cardiac vector towards lead V1
• It disappears at an older age (4-6 years)

Right Tawar Bundle Branch Block

• Right Tawar Bundle Branch Block
• Wide QRS complex > 0.12s
• Dominant QRS in V1 (rsR configuration)
• Deep S in V6
• Why is there a dominant R in V1?
• The right Tawar bundle branch is blocked
• The impulse through the left Tawar bundle branch activates the left ventricle
• and then from the left ventricle activates the right ventricle, the vector points towards V1

WPW Syndrome (Type A)

• WPW Syndrome Type A
• Shortened PQ interval < 0.12s
• Delta wave - broadened lower part of the QRS, most visible in (I, II, V4-V6)
• Type A (Kent bundle is in the left ventricle, resulting in a positive QRS in V1)
• Dominant R wave in V1
• Ventricles are activated via 2 pathways (through the AV node and Kent bundle)
• The ventricular vector then points towards the right ventricle (towards leads V1-V3)

Dextrocardia

• In dextrocardia, the heart is rotated to the right, resulting in a right axis deviation:
• Dominant R wave in aVR
• Dominant Q wave in lead I
• R wave (V1-V6) progressively decreases
• There is no preserved R wave progression
• Extremely high R wave in V1
• The main vector in dextrocardia points from V6 to V1

Muscular Dystrophy

• Muscular Dystrophy
  • It is a group of inherited disorders characterized by atrophy of muscle tissue throughout the body, including the heart
• Non-specific changes occur on the EKG
• The EKG is from a patient with muscular dystrophy
• Dominant R wave in V1
• Probably, the left ventricle is more atrophied than the right
• The vector from the dominant right ventricle points toward leads V1-V3