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cardiology > 8) OX Conduction disorders. > Flashcards

8) OX Conduction disorders. Flashcards

1
Q

what are the types of conduction disorders ?

A

sinoatrial exit block

wandering atrial pacemaker

Av block

Bundle branch block

Fascicular block

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2
Q

WHAT IS THE ETIOLOGY OF CONDUCTION DISTRUBNACES ?

A

electrolyte disblanace - hyprkalemia

digitalis intoxication , beta blockers , calcium channel blockers

Lyme disease

IHD

chagas disease

Myocarditis

Pericarditis

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3
Q

what is the classification of atrioventricular block ?

A

Incomplete

1st degree AV block

2 degree av block
mobitz type 1 / wenckeback
mobitz type 2

adavnced AV block

Complete
3 degree av block

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4
Q

what are the causes for AV block and the location the block ?

A
  • there is an increase in vagal tone = usually athletes
  • idiopathic fibrosis of conduction system
  • ischemic heart disease
  • cardiomyopathy - amyloidosis or sarcoidosis
  • infection - lyme disease , bacterial endocarditis
  • hyperkalemia
  • iatrogenic - bb , cab , digitalis , surgery *

location - proximal / distal to bundle of HIS in the atrium or AV node

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5
Q

what is the diagnosis for 1st degree av block ?

A

delay of impulse conduction from atria to ventricle is

prolonged so that the PR interval - more than 0.2 seconds or more than 5 small boxes in ECG

but no RR change

Every P wave is conducted

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6
Q

what is the treatment for first degree AV block ?

A

assessment for underlying disease

no specific treatment necessary but follow up

Pacemaker indications
if the patient exhibits wide qrs complexes - identify level of AV block (within or below bundle of His) using INTRACARDIAC ELECTROGRAM = if conduction time from bundle of his to ventricles more than 100ms = pacemaker placement
usually this is asymptomatic - symptomatic patients

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7
Q

what is the diagnosis of second degree av block type 1

A

conduction from atria to ventricle gradually slows

progressive prolongation of PR-interval (each of which is followed by a QRS-complex)

until one impulse from atria to ventricles completely blocked - one P-wave is not followed by a QRS complex!

the rr interval containing the blocked p wave is shorter than the sum of two PP intervals

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8
Q

treatment of second degree type 1 av block ?

A

asymptomatic usually - no treatment needed , just followup egg

symptomatic - dizziness , syncope , bradycardia

  • hemodynaically stable - monitoring with
    have at bedside atropine and transcutaneous pacer
    symptoms not reversible - permanent pacemaker

hemodynamically unstable
atropine -0.5-1mg iv
isoprenaline 0.5-2mg iv
if felling better- monitor with continuous cardiac telemetry and always have temporary transcutenoues cardiac pacer

after atropine not improved  - IV epinephrine 
or 
Iv dopamine 
or 
start transcutaneous pacing

prepare for transvenous pacemaker or permanent pacemaker

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9
Q

what is the diagnosis of second degree av block type 2

A

PR-interval remains CONSTANT (but an be long or normal)

intermittent (regular ) blocked p waves - and it always shows a REGULAR PATTERN

P-wave is followed by
a QRS- complex and then suddenly one (or more) P- wave is not followed by a QRS

AV block is in ratio 2(how many atrial depolarisation) :1 (how many of that reach the ventricles)
impossible to determine if AV block type 1 or two

a long rhythm strip helps

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10
Q

usually where is the conduction block in second degree av block type 2

A

distal to the AV node (in the bundle of His or even more distally in the Purkinje system)

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11
Q

what are the symptoms of second degree AV block ?

A 
bradycardia 
fatigue 
dyspnea 
chest pain 
syncope
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12
Q

what s the treatment of second degree AV block type2?

A

hemodynaically stable - monitoring with transcutaneous pacer
symptoms not reversible - permanent pacemaker

hemodynamically unstable
atropine “
isoprenaline “
if felling better- monitor with continuous cardiac telemetry and always have temporary transcutenoues cardiac pacer

after atropine not improved  - IV epinephrine 
or 
Iv dopamine 
or 
start transcutaneous pacing

prepare for transvenous pacemaker

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13
Q

what is a complication of second degree AV block mobitz type 2 ?

A

it may progress to third degree AV block and this is an unstable condition

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14
Q

what is a high grade or advanced AV block ?

A

when AV conduction ration is 3:1 or higher

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15
Q

what is 3rd degree atrioventricular block

A

when there is complete failure of conduction between the atria and ventricles

no relationship between the P-waves and the QRS complexes = AV dissociation
p waves and qrs complexes have their own regular rhythm and bear no relationship with each other , the atrial and ventricular activities are independent of each other

Ventricles contract in response to an escape rhythm (by latent pacemaker distal to SA node)

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16
Q

what are the ECG finding on 3rd degree atrioventricular branch block

A

Atria faster than ventricles!
P wave morphologically abnormal
atrial escape rhythm is less than 60 bpm

Some P-waves are in front of QRS, some P- waves inside QRS, some P- waves behind QRS,

sometimes there are 2 P-waves after one another without QRS in between

ventricles can have junctional escape rhythm or ventricular rhythm (
the more distant the impulse generation the slower the ventricle escape mechanism
and the more wider and deformed the qrs complexes

proximal to bundle of his - junctional escape rhythm = 40-60bpm
narrow qrs complex

ventricular rhythm distal to bundle of His
less than 40 bpm
wide and bizarre qrs complexes

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17
Q

what are the symptoms of third degree AV block ?

A

sudden onset of AV block results in asystole lasts until the ventricles escape mechanism takes over - leading to stokes adams attack
or cardiac arrest

loss of consciousness. Prior to an attack, a patient may be pale with hypoperfusion. Abnormal movements may be present, typically consisting of twitching after 15–20 seconds of unconsciousness

less than 40 bpm bradycardia = cerebral hypo perfusion , fatigue , dizziness syncope

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18
Q

what is the treatment of third degree AV block ?

A

hemodynamically stable
monitor with transcutaneous padding
permanent pacemaker

hemodynamically unstable
atropine
isoprenaline

temp transcutaneous or transvenous cardiac pacing
low bp - dopamine
heart failure = dobutamine

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19
Q

what does the bundle branch look like in ECG

A

the 2 ventricles do not depolarize simultaneously, but their depolarization overlaps and thus we do not get two separated QRS
but we get one very looong QRS complex

normal QRS: less or equal 0.10 sec
incomplete BBB QRS: 0.10-0.12 sec
• complete BBB QRS: greater than 0.12 sec

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20
Q

what are the different types of bundle branch block ?

A

Left
complete LBBB
INCOMPLETE LBBB

right
“”

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21
Q

where in the left ventricle wall is bundle branch block most likely to occur ?

A

in the septum
anterior wall
or at the apex of the heart

or left anterior fascicle or posterioir fascicle

22
Q

what is the aetiology of left bundle branch block ?

A

hypertrophy , dilation , fibrosis of the left ventricular myocardium

ischemic heart disease

cardiomyopathy

advanced valvular heart disease - such as aortic stenosis

hyperkalemia

lenegre disease - degenerative disease of the conducting system

digitalis

23
Q

diagnosis of incomplete left bundle branch block ?

A

QRS duration is between 0.10-0.12 s and all the typical LBBB morphology

24
Q

diagnosis of complete lbbb

A

the criteria

1) the heart rhythm must be supraventricular in origin
2) QRS is more than or equal to 120ms

3) , q wave should be absent in LEAD 1 , V5 , V6 (lateral leads)
but in the lead aVL, a narrow q wave may be present in the absence of myocardial pathology.

4) deep and broad s wave in V1 -v2 (s wave represents the completion of the ventricular depolarisation in the base of the intraventricular septum)
5) lead 1 ,v5 , v6 and AVL shows slurred R wave / notched / or broad monophasic

6) R peak time ( from the beginning of QRS complex to the peak R wave is more than 60ms in V5 and V6
but normal in V1 , V2 ,V3

lead v1 - may just have a normal rS complex (small r deep s wave)

left axis deviation may be present (lead 1 has most positive deflection , with lead 2and 3 and AVF are negative)

ALWAYS NOTE THAT with LBBB ST and T wave segments are usually opposite in direction the the QRS complex
positive t waves with positive QRS complex (positive concordance) normal
HOWEVER
negative t waves with NEGATIVE qrs complex typically abnormal and may represent myocardial injury / ischemia / infraction

25
Q

what is the treatment of left bundle branch block

A

in young if there are no underlying problems that is associated with left bundle branch block then no treatment is necessary

in older people with coronary heart disease - greater risk of death
an AGGRESIVE evaluation is necessary if they have new onset bundle branch block
if symptomatic and having conduction problem
- may need permanent pacemaker

heart failure with left bundle branch lock :
cardiac resynchronisation therapy - helps the ventricles contract at the same time

26
Q

what are the causes for RBBB?

A

repair of ventricle septal defect

right ventriculotomy

right ventricle hypertrophy

increase risk in those that live in high altitude

EBSTEIN anamoly

brugada syndrome

27
Q

what is the diagnostic criteria for complete right bundle branch block ?

A

criteria

1) heart rhythm must be supraventricular
2) qrs duration more than 120ms (wide) *

3) secondary R wave in V1 or V3
detonated by rsR or rsr or rSR *

4) wide and slurred s waves in the lateral leads 1 , avl v5- V6

5) normal r wave peak time in V5 and V6
but V1-v2 is more than 50ms

the one with asterisk are needed to make diagnosis

28
Q

what is the criteria for incomplete bundle branch block ?

A

same as complete except the qrs duration is less than 120ms

29
Q

in bradycardia what is the clinical manifestations ?

A

if 3-5 sec = paleness and dizziness

10-15 - loss of consciousness

20-30sec - seizures

30-60 sec - apnea

more than 3 min - brain death

30
Q

what causes SAN node dysfunction ?

A

extrinsic
carotid sinus hyperactivity
vasovagal stimulation
bb , cab , digoxin , anti arrhythmic class 1 and 3

intrinsic
chronic and acute MI
SICK sinus syndrome
inflammatory pericarditis or myocarditis

31
Q

how many types of sino atrial exist blocks are there ?

A

first degree SA block

second degree SA block - type 1 - mobitz (wenckebach block)
type 2 - mobitz 2

third degree sa block

32
Q

what is first degree san block ?

A

lag between SAN node fires and actual depolarisation of atria

33
Q

how can we diagnose an first degree SAN node block ?

A

cannot be detectable by ECG

only detected by an electrophysiology stay

34
Q

is differentiating between the two types of SAN node block necessary ?

A

differentiation between electrocardiographically but not clinical important

35
Q

how do we diagnose second degree SAN block type 1 ?

A

ONLY second degree of SAN nose block that can be recognised on surface ECG

wenkebach - rhythm is irregular
RR or PP interval gets smaller while PR INTERVAL REMAINS CONSTANT
until a qrs segment is blocked or missing

the blocked duration is less than the two preceding pp / rr interval

.The pause duration is less than the two preceding PP intervals.

the pp interval following the pause is greater than the interval just before the pause

36
Q

how do we diagnose SAN node block type 2 ?

A

regular rhythm which is normal or slow , pp intervals are fairly constant

follow by a pause - no p or QRS
pause is a MULTIPLE OF THE PP INTERVAL (2-4) usually twice the pp interval

37
Q

how do we diagnose a third degree SAN node block ?

A

no SAN node conduction
ECG no p waves

junctional rhythm ensues

If no junctional escape rhythm is present, a long pause resulting in asystole

38
Q

what is the emergency treatment of sinoatrial block ?

A

atropine sulfate
or transcutaneous pacing

permanent pacemaker

39
Q

how do we diagnose a wandering atrial pacemaker ?

A

Wandering atrial pacemaker occurs when multiple areas (ectopic foci) within the atrium generate consecutive action potentials that are all conducted to the ventricles

three morphologically different p waves especially on lead 2

rate lower than 100 bpm (normal)
different P-r intervals / different pp intervals
EXCLUSION OF FREQUENT ATRIAl PREMATURE BEATS

40
Q

what are types of fascicular blocks

A

left anterior fascicular bock

left posterior fascicular block

bifascicular block

trifascicular block

41
Q

what does left anterior fascicular block look in egg

A

action potential is only conducted through the left posterior fascicle

major polar depolarisation is left wards and upwards

1) left axis deviation of -45 to -90
lead 1 most positive , with lead 2 and 3 negative
AND Avf

2) large positive voltages in lead 1 and AVL the left sided leads
3) we also see large negative voltage inferiority - in lead 2 , lead 3 , avF negative

qrs normal or slightly prolongerd

4) q(small q wave) R complex in lead 1 and AVL

5) rS complexes in leads 2,3 (especially) ,aVF
the inferior leads

6) delayed r wave peak (endometrial to epicardium) time in aVL
more than 45s

42
Q

LAFB cannot be diagnosed prior to what condition

A

LAFB cannot be diagnosed when a prior inferior wall myocardial infarction (IMI) is evident on the ECG.

IMI can also cause extreme left-axis deviation, but will manifest with Q-waves in the inferior leads II, III, and aVF. By contrast, QRS complexes in the inferior leads should begin with r-waves in LAFB.

43
Q

causes of left anterior fascicular block?

A

AMI

hypertensive heart disease

degenerative disease of conducting system

myocardial fibrosis

44
Q

what is the diagnosis of left posterior fascicular block ?

A

1) right axis deviation - lead 1 positive
lead 2 positive
lead 3 the most positive deflection
AVF positive

2) qrs norma or slightly widened
3) rS complexes in lead 1 and AVL
4) qR complexes in lead 2 , lead 3 and aVF inferior leads
2) no ST segment or t wave changes

must have absence of other c causes of right axis deviation - lateral myocardial infraction , dextrocardia , right ventricular hypertrophy

45
Q

what is the cause of left posterioir fascicular block ?

A

left bundle conduction system made of left anterior and posterioir fascicle

left posterioir is shorter and thicker than left anterior fasciale left posterioir also gets dual blood supply both from the left and right coronary artery

  • MULTIVESSEL CORONARY ARTERY DISEASE MOST COMMON
46
Q

what is bifascicular bundle branch block ?

A

RBBB with either left anterior or left posterioir fascicular block

47
Q

what is the diagnostic criteria for bifascicular bundle branch block ?

A

prolongation of the QRS duration 0.12 s or longer

rSR in V1 - the R being broad and slurred

wide and slurred s wave in lead 1 ,V5 and V6

with left or right axis dilation

48
Q

what are the causes for bifascicular block ?

A

CAD

degenerative disease of the conducting system

aortic stenosis

hypertensive heart disease

49
Q

what is trifascicular block ?

A

the combination of RBBB and LAFB and long PR interval

implies the conduction is delayed in the third fascicle

50
Q

what are the indications for permanent pacemaking ?

A

third degree av block

asysotle for more than or equal to 30seconda or any escape rate of less than 40pbm WHILST AWAY

AFTER CATHETER ABLTAION OF THE av junction / node

second degree AV lock with symptomatic bradycardia

cardiology (32 decks)

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