Lecture 6 (Intraventricular Conduction Defects) Flashcards Preview

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Flashcards in Lecture 6 (Intraventricular Conduction Defects) Deck (40)
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1

Right atrial enlargement cause

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

2

Left atrial enlargement cause

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

3

leads to asses atrial enlargement

II and V1

4

RAE finding on EKG

increased amplitude of the first part of the p wave

5

LAE finding on EKG

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

6

Ventricular Hypertrophy Causes

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

7

Ventricular Hypertrophy general EKG findings

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)

8

RVH EKG findings

-most common characteristic in limb leads is RAD
-in precordial leads R waves are more positiv which lie closer to lead V1

9

LVH EKG findings

-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)

10

Bundle Branches

Bundle of His divides into right and left bundle branches
-left bundle branch divides into SEPTAL, ANTERIOR, and POSTERIOR fascicles

11

Normal QRS complex

narrow

12

Bundle Branch Block definition

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

13

Bundle Branch Block EKG findings

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

14

RR' configuration in chest leads

-2 peaks or rabbit ears
-the delayed ventricle is represented by R'

15

Possible sites of BBB

-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

16

RBBB Criteria

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'

17

RBBB seen in

CAD, Pulmonary embolism

18

Frontal plane QRS axis in RBBB

should be in normal range (0-+90)

19

ST-T waves in RBBB

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

20

LBBB

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

21

BBB plus LVH or RVH

-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

22

Hemiblock definition

when one of the fascicles of the LBB is blocked

23

3 LBB fascicles

anterior, posterior, septal
-septal not involved in hemiblocks

24

Key to detecting a hemiblock

-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

25

Left Anterior Hemiblock definition

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

26

Left Anterior Hemiblock EKG findings

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

27

Left Posterior Hemiblock definition

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

28

Left Posterior Hemiblock EKG findings

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

29

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

-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

30

Bifascicular Block definition

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