ECG: Bundle Branch Blocks/Hemiblocks (Johnston)

Question 1

Define intrinsic deflection (ID)

Answer 1

Time lapse from beginning of the QRS to the peak of the R wave

Question 2

During ventricular depolarization the septum is activated in which direction?

Answer 2

From L –> R

Question 3

Which feature of the QRS complex is characteristic of bundle branch blocks?

Answer 3

Wide QRS (>0.12 sec) = >3 small squares

Question 4

List 6 causes of rsR’ variants in V1-V2

Answer 4

• Normal
• Pectus or straight back
• RV diastolic volume overload
• WPW syndrome
• RVH
• Duchenne dystrophy

Question 5

What are 4 underlying etiologies where LBBB is more likely to occur?

Answer 5

• HTN
• Ischemia
• Aortic stenosis
• Cardiomyopathy

Question 6

LBBB with RAD is usually due to what?

Answer 6

Congestive Cardiomyopathy

Question 7

In LBBB which 2 leads share similar features with V6?

Answer 7

Lead I and AVL (point in similar direction)

Question 8

If T wave polarity is in the same direction of the QRS complex, it is called what type of T wave change?

Usually due to what?

Answer 8

• Primary T wave change
• Due to ischemia

Question 9

What type of block is this?

Answer 9

Left Anterior Hemiblock

Question 10

What type of axis deviation is associated with a left anterior hemiblock and a left posterior hemiblock?

Answer 10

• LAH is associated with LAD
• LPH is associated with RAD

Question 11

What is the morphology of the Q and R waves associated with a left anterior hemiblock and in which leads?

Answer 11

• Small Q in leads I and aVL
• Small R in leads II, III, and aVF

Question 12

What is the morphology of the Q and R waves associated with a left posterior hemiblock and in which leads?

Answer 12

• Small R in leads I and aVL
• Small Q in leads II, III, and aVF

Question 13

What is the typical etiology of left anterior hemiblocks?

Answer 13

• Disease in conduction system
• Often associated w/ MI (LAD - occlusion)

Question 14

Interpret this EKG

Answer 14

Left Anteior Hemiblock

Question 15

Interpret this EKG

Answer 15

Left Anterior Hemiblock

Question 16

Interpret this EKG

Answer 16

Bifascicular block: RBBB + Left Anterior Hemiblock

Question 17

Interpret this EKG

Answer 17

Left Posteior Hemiblock

Question 18

The consideration for left posterior hemiblock requires that there be no evidence of what?

Answer 18

Right ventricular hypertrophy

Question 19

Interpret this ECG (i.e., axis and rhythm)

Answer 19

RAD w/ left posterior hemiblock and RBBB