Lecture 6 (Intraventricular Conduction Defects)

Question 1

Right atrial enlargement cause

Answer 1

chronic pulmonary diseases may cause it in the response to the need for greater filling pressures in the right ventricles

Question 2

Left atrial enlargement cause

Answer 2

mitral regurgitation due to blood being forced backwards into the left atria

Question 3

leads to asses atrial enlargement

Answer 3

II and V1

Question 4

RAE finding on EKG

Answer 4

increased amplitude of the first part of the p wave

Question 5

LAE finding on EKG

Answer 5

increased NEGATIVE amplitude in the terminal portion of the p wave in V1 Increased duration or width of the P wave

Question 6

Ventricular Hypertrophy Causes

Answer 6

caused by chronic poOrly treated HTN-bc there is more muscle to depolarize there is more electrical activity occuring in the hypertrophied muscle
-reflected by changes in amplitude of portions of the QRS complex

Question 7

Ventricular Hypertrophy general EKG findings

Answer 7

V1 electrode normally positive-wave of depolarization moving through LV mmoving away from electrode
-mainly produces negative QRS complexes (short R with larger S waves)

Question 8

RVH EKG findings

Answer 8

• most common characteristic in limb leads is RAD

- in precordial leads R waves are more positiv which lie closer to lead V1

Question 9

LVH EKG findings

Answer 9

• increased R wave amplitude in precordial leads over LV (V5-V6)
• S waves are smaller in leads over LV (V5-V6) but larger in leads over RV (leads V1-0V2)

Question 10

Bundle Branches

Answer 10

Bundle of His divides into right and left bundle branches

-left bundle branch divides into SEPTAL, ANTERIOR, and POSTERIOR fascicles

Question 11

Normal QRS complex

Answer 11

narrow

Question 12

Bundle Branch Block definition

Answer 12

• results in one or both bundle branches failing to conduct impulses
• produces delay in depolarization of the ventricle it supplies

Question 13

Bundle Branch Block EKG findings

Answer 13

QRS MUST BE >/=0.12s
FOR BBB-RR’ configuration with normal QRS interval is called an “INCOMPLETE BBB”-widened QRS complex-RR’ configuration in chest leads

Question 14

RR’ configuration in chest leads

Answer 14

• 2 peaks or rabbit ears

- the delayed ventricle is represented by R’

Question 15

Possible sites of BBB

Answer 15

• RBBB (right bundle branch block)
• LBBB (left BBB)
• LAHB/LAFB (left anterior hemiblock or fascicular block)
• LPHB/LPFB(left posterior hemiblock or fascicular block
• any combination of the above

Question 16

RBBB Criteria

Answer 16

Main ones:
-Prolonged QRS (complete has QRS >0.12s)
-M-shaped RR' in lead V1
-Wide S wave in Lead 1 and V6
Others:-LV depolarizes normally but RV is delayed, represented by R'

Question 17

RBBB seen in

Answer 17

CAD, Pulmonary embolism

Question 18

Frontal plane QRS axis in RBBB

Answer 18

should be in normal range (0-+90)

Question 19

ST-T waves in RBBB

Answer 19

normal ST-T waves in RBBB should be oriented opposite to the direction of the terminal QRS forced

Question 20

LBBB

Answer 20

Main criteria:
-Prolonged QRS
-Wide R wave in leads 1 and V6
Other criteria:
-QRS waves have tall R waves with prolonged duration and either nothced or flattened tops of the complexes
-true rabbit ears are less likely than in RBBB
-Leads over RV show reciprocal, broad, deep S waves

Question 21

BBB plus LVH or RVH

Answer 21

• NOT POSSIBLE TO DIAGNOSE LVH OR RVH IN THE SETTING OF LBBB(for LVH) or RBBB(for RVH)
• some texts indicate that RVH is likely if the R’ in V1 is >15mm

Question 22

Hemiblock definition

Answer 22

when one of the fascicles of the LBB is blocked

Question 23

3 LBB fascicles

Answer 23

anterior, posterior, septal

-septal not involved in hemiblocks

Question 24

Key to detecting a hemiblock

Answer 24

• CHANGE IN THE QRS AXIS but the QRS DURATION IS NOT PROLONGED, unless there is concomitant RBBB
• the right bundle does not divide into separate fascicles

Question 25

Left Anterior Hemiblock definition

Answer 25

blocked conduction down the left anterior fascicle | -mean axis is directed up and to the left

Question 26

Left Anterior Hemiblock EKG findings

Answer 26

- LAD (minus 45-minus 90)* - tall R waves in leads 1 - Deep S waves in aVf - Usually normal QRS duration

Question 27

Left Posterior Hemiblock definition

Answer 27

posterior fascicle is blocks | -depolarization moves downward and to the right

Question 28

Left Posterior Hemiblock EKG findings

Answer 28

- RAD (>/=+120 TO +180)* - normal QRS +120) - no evidence of RVH or anterior infarction

Question 29

What do you want to do for left posterior hemiblock before diagnosing?

Answer 29

- exclude other causes of RAD: cor pulmonale, pulm HTN etc - no evidence of RVH or anterior infarction - LPHB may be difficult to dx w/o prior EKGs

Question 30

Bifascicular Block definition

Answer 30

- RBBB plus with LAHB or LPHB (LPHB is uncommon) | - features of RBBB plus frontal plane features of the fascicular block-axis deviation

Question 31

Bifascicular Block EKG findings

Answer 31

- RBBB + LAHB (LAD of -45 to -90) | - RBBB + LPHB (RAD of >+120)

Question 32

Nonspecific IVCD

Answer 32

-when either QRS IS PROLONGED w/o features of RBBB or LBBB this is called nonspecific intraventricular delay (or defect)

Question 33

Nonspecific IVCD EKG findings

Answer 33

- QRS duration >0.11s indication slowed conduction of the ventricles - criteria for specific bundle branch or fascicular blocks not met

Question 34

Causes of nonspecific IVCD

Answer 34

- Ventricular hypertrophy (esp LVH) - MI (so called PERIINFARCTION BLOCKS) - Certain antiarrhythmic drugs (quinidine, flecainide) - Hyperkalemia

Question 35

Preexcitation Syndrome

Answer 35

- accessory conduction pathways sometimes exist between atria and ventricles - Bypass AV node and bundle of His and allow early depolarization of ventricles - RESULTS IN SHORT PR INTERVAL

Question 36

Preexcitation Syndrome examples

Answer 36

- WPW:bundle of kent | - LGL: James fibers

Question 37

Wolff-Parkinson-White Syndrome EKG findings

Answer 37

- PR interval

Question 38

WPW patients at risk for:

Answer 38

PSVT

Question 39

Delta Wave

Answer 39

-seen in WPW-sloping upward of PR segment...cannot calculate PR segment

Question 40

Lown-Ganong -Levine Syndrome

Answer 40

-Intranodal accessory pathway (JAMES FIBERS) bypasses the normal delay in AV node-PR interval