• Wide QRS Complex
• Causes of RBBB
• Heart Vector and RBBB
• RBBB and Leads (V1, V6)
• ECG and RBBB
• ECG and Incomplete RBBB
• Functional RBBB and Ashman Phenomenon

Wide QRS Complex

Wide QRS Complex (≥ 0.12s)

• In Right Bundle Branch Block (RBBB)
• The impulse is blocked in the right bundle branch
• Supraventricular impulse activates the ventricles only through the left bundle branch
• Which later divides into the left anterior and left posterior fascicles
• The left ventricle is activated first
• Then the impulse passes through the myocardium to the right ventricle and activates it
• The impulse spreads through the myocardium more slowly than through the bundle branches
• Activation of the right ventricle is therefore delayed
• This results in a wide QRS complex ≥ 0.12s (≥ 3 squares)

Heart Vector and RBBB

Ventricular Activation in Right Bundle Branch Block

• Both ventricles are activated only through the left bundle branch, with impulse activation occurring sequentially
• During the activation of different parts of the ventricles, heart vectors are generated
• 1. First, the interventricular septum is activated
• A small initial vector (V_I) is created, directed to the right (1)
• The vector is small because the myocardial mass of the interventricular septum is small
• 2. Next, the left ventricle is activated
• The impulse exits the left bundle branch and activates the massive myocardium of the left ventricle
• A main largest heart vector (V_M) is created, directed to the left (2)
• 3. Then, the right ventricle is activated
• The impulse slowly passes to the right ventricle through the myocardium (not through the blocked right bundle branch)
• A wide QRS complex ≥ 0.12s is created
• A small terminal vector (V_T) is generated, directed to the right
• Vectors and ECG leads should be visualized in 3D space
• If a vector points towards an ECG lead, it creates a positive deflection
• If a vector points away from an ECG lead, it creates a negative deflection

ECG and RBBB

• Wide QRS ≥ 0,12s (≥ 3 squares)
• In V1, the QRS has an "M" shape
• Also in other right-sided leads (V1-V3)
• The second rabbit ear is almost always larger
• Can present with configurations such as: rsr', rsR', rSR'
• In V6, there is a wide S wave > 40ms
• Also in other lateral leads (V5-6, aVL, I)
• QRS has a "W" shape
• In V1-V3, there are ST depressions or negative T waves
• Delayed activation of the right ventricle causes repolarization changes

RBBB (V1)

• Wide QRS ≥ 0.12s
• Negative T wave
• V1 (rsR' configuration)

RBBB (V6)

• Wide QRS ≥ 0.12s
• V6 (wide S wave)

ECG and Incomplete RBBB

• The right bundle branch is impaired but not interrupted ("cut off")
• Conducts impulses more slowly
• The only difference on ECG compared to complete block is the width of the QRS complex
• Complete RBBB
• QRS width ≥ 0.12s
• Incomplete RBBB
• QRS width 0.1 - 0.12s

Functional RBBB and Ashman Phenomenon

• It is a temporary RBBB that appears on the ECG and then disappears
• Functional RBBB occurs when an impulse arrives at the branch too early, during the refractory period
The branch blocks this impulse
• This premature impulse can reach the branch during
• Atrial extrasystole
• Junctional extrasystole
• Atrial fibrillation

• With a lengthening RR interval, the refractory period of the conduction system also lengthens
• Ashman phenomenon is aberrant conduction that occurs when a lengthened RR interval is followed by a shortened RR interval
• Shortened RR interval has a prolonged refractory period
• which has not had time to shorten from the previous lengthened RR interval
  
  
• It is true that the right bundle branch (RBB) has a longer refractory period than the left bundle branch (LBB)
• If an impulse travels through the AV node to the ventricles at a time
• when the right bundle branch is in the refractory period
• it results in functional RBBB
• The functional block most commonly occurs during atrial fibrillation
• When a long RR interval is followed by a short RR with a QRS complex (which has the appearance of RBBB)

Right Bundle Branch Block

• Wide QRS ≥ 0.12s
• In V1 (V2) there is qR
• In V6 (V5, I) there is wide S
• In V1-3 there are negative T waves

Right Bundle Branch Block

• Wide QRS ≥ 0.12s
• In V1 there is rSR'
• In V6 (V5-6, I, aVL) there is wide S
• In V1-3 there are negative T waves

Incomplete Right Bundle Branch Block

• In V1 there is RSr'
• In V5 and I there is wide S
• In V1-3 there are negative T waves
• Narrow QRS < 0.12s
• The patient meets all criteria for RBBB, but the QRS complex is narrow
• Narrow QRS indicates incomplete RBBB