Conduction Abnormalities

Question 1

broad negative p-wave in V1 means?

Answer 1

left atrial abnormality

Question 2

Requirements for normal QRS and T wave:

Answer 2

• normal RV and LV size
• normal myocardial perfusion (no ischemia)
• normal rapid impulse conduction
• normal activation sequence (no pre-excitation)

Question 3

Abnormal intraventricular conduction - bundle branch blocks:

-appearance on ECG?

Answer 3

• for some reason one of the ventricles gets the impulse later than the other ventricle
• WIDE QRS

Question 4

Wide QRS

• when?
• why?

Answer 4

• BBB to a ventricle
• ventricular tachycardia
• ventricular premature
• paced rhythm (pacer put in R ventricle)

-the electrical signal moves through the MUSCLE since the conducting system is broken

Question 5

LBBB morphology:

Answer 5

• broad QS in V1

- broad, slurred R wave in V6

Question 6

RBBB morphology:

Answer 6

• broad QRS with rSR’ pattern in V1**
• deep, broad S wave in V6
• wide S in Lead 1
• QRS>0.12sec
• T-wave is usually wide and negative (opposite) to QRS direction

Question 7

Unifasicular Block - Left ANTERIOR fasicular block (LAFB) morphology:

Answer 7

• MORE COMMON
• left axis deviation, at least -45 degrees (small Q in Lead 1, avL & small R in Lead 2, 3, avF)
• normal QRS duration
• late intrinsicoid in avL
• inc QRS voltage in limb leads

Question 8

Unifasicular Block - Left POSTERIOR fasicular block (LPFB) morphology:

Answer 8

• RARE
• right axis deviation, more that +120 or more (small R in Lead1, avL & small Q in Leads 2, 3 and avF)
• normal QRS
• late intrinsicoid in avF
• inc QRS voltage in limb leads
• no evidence of RVH

Question 9

Bifascicular blocks

Answer 9

• RBBB + LAFB (more common)
• RBBB + LPFB (less common)
• LBBB

Question 10

Left bundle branch block

-morphology?

Answer 10

• wide (>0.12sec) QRS complex
• V1 has QS or rS complex
• V6 shows late intrinsicoid deflection, no Q, monophasic R wave
• Lead 1 shows monophasic R, no Q

Question 11

trifascicular blocks

-definition?

Answer 11

• block in 3 fascicles - usually RBBB plus 2 divisions of the left bundle
• incomplete block of left bundle

Question 12

Block in all fascicles is complete=

Answer 12

3rd degree AV block

Question 13

Most common trifascicular block?

Answer 13

RBBB+LAFB+first degree AV block

Question 14

bundle branch block vs fascicular block

-effect on QRS?

Answer 14

• BBB prolong (WIDEN) QRS

- fascicular blocks DO NOT widen QRS*

Question 15

LBBB v RBBB

-effect on amplitude?

Answer 15

LBBB increases QRS amplitude
RBBB DOES NOT inc QRS amp

(not really useful - a whole bunch of pathologies can affect amp)

Question 16

Which blocks cause L-axis deviation?

Answer 16

• LBBB often

- LAFB

Question 17

Which blocks cause R-axis deviation?

Answer 17

• LPFB

- RBBB VARIES!!!