Bundle Branch Blocks

Question 1

Right Bundle Branch Block:

• EKG
• Complete RBBB

Answer 1

• Impulse travels left to right.
  Right depol is seen after left.
  Delay of the right ventricle causes the vector to shift in a rightward anterior direction.
• Prolonged QRS (>/= .12)
  Abnormally late portion of QRS is directed toward the right vent and away from the left.
  Lead I typical has broad S wave.
  V1 Contains RSR complex.

Question 2

Left Bundle Branch Block

• EKG
• Significance

Answer 2

• Prolonged QRS complex (>/= .12) and bizzare.
  Leads I, aVL, V5 and V6 typically wide and notched QRS (due to visual of lateral aspect) .
  Leads V1, V2, and V3 contain deep S waves.
  Leads I, aVL, V5 and V6 contain tall R waves.
• Usually indicates significant and wide spread myocardial disease.
  Causes: Drugs, MI, Electrolytes, and Degenerative Disease.
  Masks Ischemic changes associated with MI.
  Negates chance of localizing MI.

Question 3

Differentiating LBBB and RBBB

- 4 Steps

Answer 3

• Determine QRS is consistently greater.
• View QRS in V1
• Find J point
• Draw horizontal line from J point to beginning of QRS. If triangle points up RBBB, points down LBBB.

Question 4

Left Posterior Hemi-block

• QRS
• Principle findings
• Causes

Answer 4

• Typically not prolonged and remain relatively normal.
• Right ward shift in QRS Axis, difficult to diagnose. >/= 120 to consider LPHB.
• Degenerative disease or ischemic heart disease.

Question 5

Chamber Enlargement

• Hypertension
• Causes
• RAE relation to RVH
• LAE relation to LVH

Answer 5

• Enlargement w/o any additional cells (stretching).
• Any disease that causes long-term increased pressure in any chamber of the heart, Can involve any chamber.
• RAE is precursor to RVH, commonly associated with pulmonary disease such as COPD.
• LAE os precursor to LVH, commonly caused by long-term HTN.

Question 6

Chamber Enlargement EKG Representation

• First Half of P wave
• Second Half of P wave
• RAE
• LAE
• Best View of Atrium
• RVH/LVH
• LVH
• Recognition of LVH
• Standard method of Enlargement

Answer 6

• Represents right atrial depol
• Represents left atrial depol
• Appears on 12 lead as tall spiked beginning of P wave, greater than 2 mm or 2 small boxes.
• Appears as biphasic widening of p wave of 2.5 mm of 2 1/2 small boxes.
• Leads II, aVL, V1, and V2
• Both can appear as abnormally deep Swaves or tall wave in precordial leads.
• V1/V2 adds height to deeper S waves and V5/V6 taller R waves. Sum may of >/= 35 indicates LVH.
• Important because patterns mimic ST elevation.
• Endocardiogram, 12-lead only detects about 50%.