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Cardiovascular Exam II > AV Blocks, BBBs, Hemiblocks, & Hypertrophy > Flashcards

AV Blocks, BBBs, Hemiblocks, & Hypertrophy Flashcards

1
Q

A first degree heart block slows the _____ conduction, prolonging the _______ on ECG to more than ______ sec

A

AV node; PR interval 0.2 (more than one large square)

Note that PR remains consistently lengthened cycle to cycle

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2
Q

Second degree AV blocks allow some P waves to conduct to the ventricles (producing QRS response), while some are blocked —- leaving lone P waves without an associated QRS. What are the 2 types of second degree AV blocks?

A

Wenckebach (type I) = block occurs in AV node; produce series of cycles with progressive blocking of AV node conduction until final P wave is totally blocked, eliminating QRS response (progressive prolonging of PR interval). Each repeating Wenckebach series has a consistent P:QRS ratio like 3:2, 4:3, 5:4, etc. (one less QRS than P waves in the series)

Mobitz (type II) = block occurs below AV node (Purkinje fibers, His bundle, or bundle branches). Produce a series of cycles consisting of one normal cycle preceded by a series of paced P waves that fail to conduct through AV node (no QRS response). Each repeating Mobitz series has a consistent P:QRS ratio like 3:1, 4:1, 5:1, etc.

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3
Q

What is a 2:1 AV block?

A

Mobitz second degree AV block in which there is 2:1 ratio of 2 P waves to 1 QRS response

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4
Q

Both Wenckebach and Mobitz have missing QRSs so how can we differentiate between 2:1 Wenckebach and 2:1 Mobitz?

A

If the PR interval is lengthened, but the QRS is normal = most likely Wenckebach

If the PR interval is normal but the QRS is widened =most likely Mobitz

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5
Q

ECG findings with 3rd degree (complete) AV block

A

Atria are independently paced by SA node, while (depending on location of block) ventricles are independently paced

[P waves occur independently of the slower paced QRS complexes]

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6
Q

If a complete AV block occurs above the AV junction (i.e., in the upper AV node), then a junctional focus esccapes to pace the ventricles. On EKG, QRS’s appear ______ with a ventricular rate of ______/min

A

Normal (narrow); 40-60

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7
Q

When a complete AV block occurs below the AV junction, a ventricular focus escapes overdrive suppression to pace the ventricles at its slow inherent rate of only _____/min with _______ QRS’s; so slow that cerebral blood flow is compromised and _____ may ensue

A

20-40; widened; syncope

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8
Q

Intrinsic vs. extrinsic etiologies of SA node dysfunction

A

Intrinsic = degenerative, ischemic, inflammatory, infiltrative (e.g., amyloid), or rare mutations in Na+ channel or pacemaker current genes

Extrinsic = drugs like beta blockers, Ca channel blockers, digoxin; autonomic dysfunction, hypothyroidism

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9
Q

Symptoms of SA node dysfunction

A

Sx are d/t bradycardia (fatigue, weakness, lightheadedness, syncope) and/or episodes of associated tachycardia (e.g., rapid palpitations, angina) in pts with sick sinus syndrome

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10
Q

First degree AV blocks may be normal or secondary to increased _____ tone or drugs (e.g., beta blockers, diltiazem, verapamil, or digoxin)

A

Vagal (parasympathetic)

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11
Q

Causes of Wenckebach second degree AV block

A

Seen with drug intoxication (digitalis, beta blockers), increased vagal tone, inferior MI

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12
Q

Does Wenckebach require tx?

A

Only if symptomatic — can use atropine or temporary pacemaker

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13
Q

T/F: permanent pacemaker is indicated in Mobitz II second degree AV block

A

True

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14
Q

Autonomic causes of AV block

A

Carotid sinus hypersensitivity

Vasovagal

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15
Q

Metabolic/endocrine causes of AV block

A

Hyperkalemia
Hypermagnesemia
Hypothyroid
Adrenal insufficiency

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16
Q

Drug-related causes of AV block

A 
Beta blockers
Adenosine
Ca chanel blockers
Antiarrhythmics (classs I and III)
Digitalis
Lithium
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17
Q

Infectious causes of AV block

A 
Endocarditis
TB
Lyme dz
Chagas
Syphilis
Diphtheria
Toxoplasmosis
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18
Q

Heritable/congenital causes of AV block

A

Congenital heart dz
Maternal SLE
Kearns-sayre syndrome
Myotonic dystrophy

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19
Q

Inflammatory causes of AV block

A

SLE
MCTD
RA
Sceroderma

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20
Q

Infiltrative causes of AV block

A

Amyloidosis
Sarcoid
Hemochromatosis

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21
Q

Neoplastic/traumatic causes of AV block

A 
Lymphoma
Mesothelioma
Melanoma
Radiation
Catheter ablation
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22
Q

Comorbid conditions associated with 1st degree AV block

A

Atherosclerosis
HTN
Diabetes

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23
Q

What type of AV block is associated with inferior MI vs. anterior MI?

A

Inferior MI = Wenckebach

Anterior MI = Mobitz (II)

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24
Q

Underlying pathology in Wenckebach vs. Mobitz II AV blocks

A

Wenckebach: RCA disease, diaphragmatic infarct, edema around AV node

Mobitz II: LAD coronary artery disease, large anteroseptal infarct, chronic degeneration of conduction system

25
Q

How do you treat 3rd degree AV block

A

Pacemaker

26
Q

Characteristic EKG finding of a bundle branch block

A

Wide QRS with 2 peaks (representing non-simultaneous depolarization of the right and left ventricles)

ST segment — T waves slope off in opposite direction to QRS [if T waves are concordant it suggests ischemia or MI]

27
Q

With bundle branch block, the QRS is widened to ____ seconds or more

A

0.12 (or 3 small squares)

28
Q

If there is a bundle branch block, look at leads ___ and ____, and leads ____ and ____ for the R1R’

A

V1, V2 (right chest leads); V5, V6 (left chest leads)

29
Q

If there is an R,R’ in chest leads V1 or V2, there is probably a _____ bundle branch block

A

Right

30
Q

A quick trick to figure out what type of BBB there is is to look at V1. If V1 is positive, it is considered ____ BBB; if it is negative, it is ____ BBB

A

Right; left

31
Q

In normal ventricular conduction, what is the origin of a small q wave in V5 and V6?

A

Right ventricular conduction

[v5/v6 is apex of heart; a small Q wave there means that some forces are travelling to RV to depolarize]

32
Q

Which side of the septum is activated first in RBBB?

A

Left

33
Q

In RBBB, why is there an S wave in V6?

A

V6 is the apex of the heart, S wave is small depolarization of left ventricle

34
Q

Causes of prominent R wave in V1-V2

A 
Normal
Pectus or straight back
RV diastolic volume overload
WPW syndrome
RVH
Duchenne dystrophy
35
Q

LBBB is more apt to occur with what 4 conditions?

A

HTN, ischemia, aortic stenosis, cardiomyopathy

36
Q

LBBB with ____ axis deviation may be associated with more myocardial dysfunction, more dz in conduction system, and possibly higher mortality, while LBBB with ____ axis deviation is associated with congestive cardiomyopathy.

A

Left; right

37
Q

What are hemiblocks?

A

The left bundle branch subdivides into anterior and posterior divisions; a hemiblock is a block of either of these divisions

38
Q

The ______ usually renders blood supply to the SA node, AV node, bundle of His, and a variable twig to the posterior division of the left bundle branch; note that the _____ also sends a variable twig to the posterior division of the left bundle branch

A

RCA; LCA

39
Q

A total occlusion of the anterior descending branch of the LCA may cause a subsequent _____ with _____ hemiblock, often associated with ____ axis deviation

A

RBBB; anterior; left

40
Q

T/F: with anterior hemiblock, the QRS is widened only to .10 to .12 seconds, but association with other blocks of the bundle branch system will widen the QRS more

A

True

41
Q

Anterior hemiblock is a block of the anterior division of the LBB. Finding a _____ in lead I and a wide and/or deep S wave in lead _____ helps to confirm the dx of anterior hemiblock

A

Q wave; III

[Q1S3]

42
Q

With right bundle branch block, the mean QRS vector is within the normal range or shows minimal ____ axis deviation

However, when a pt develops a RBBB with _____ axis deviation, this is probably caused by anterior hemiblock, particularly if there is an acute anterior infarct

A

Right; left

43
Q

Why are pure, isolated posterior hemiblocks rare?

A

Posterior division is short, thick, and often has dual blood supply

44
Q

An inferior infarct may impair the blood supply to the ______ division of the left bundle branch

A

Posterior

45
Q

Posterior hemiblocks cause ____ axis deviation due to late, unopposed depolarization forces toward that side.

When posterior hemiblock is suspected, look for deep or unusually wide ____ wave in lead I and ____ wave in lead III to help confirm diagnosis

A

Right

S; Q

[S1Q3]

46
Q

A bundle branch block with a hemiblock is called a ______ block

A

Fascicular

47
Q

What is a bifascicular block?

A

Generally refers to RBBB with block of either anterior or posterior division of the left bundle branch

48
Q

A continuous normal EKG pattern with intermittent wide QRS pattern usually indicates intermittent ______

A continuous normal EKG pattern with intermittent change in QRS axis (e.g., upright QRS’s that transiently change to downward QRS’s) usually indicates intermittent _____

A

BBB; hemiblock

49
Q

Lead ____ is directly over the atria, so the ___ wave in that lead is our best source of info about atrial enlargement

A

V1; P

50
Q

The chest electrode that records V1 is considered _____ (+ or -)

A

positive

51
Q

How do you tell if it is the right vs. the left atrium that is enlarged based on EKG?

A

If initial component of diphasic P wave in V1 is larger, then it is right atrial enlargement [also, if height of P wave in any limb lead exceeds 2.5 mm, even if not diphasic, it is likely right atrial enlargement]

If terminal portion of diphasic P wave in V1 is large and wide, there is left atrial enlargement

52
Q

The QRS represents ventricular depolarization, so the QRS should be able to represent presence of ventricular hypertophy. In lead V1, the QRS is primarily ______ (positive or negative), and therefore the ___ wave is usually very short

A

negative; R

53
Q

The QRS represents ventricular depolarization, so the QRS should be able to represent presence of ventricular hypertophy. In lead V1, the QRS is primarily negative, and therefore the R wave is usually very short. What changes occur with right ventricular hypertrophy?

A

QRS appears more positive with large R wave in V1

Also note that the R wave of V1 will get progressively smaller fom V2 to V3 to V4, etc.

[the S wave in lead V1 will be smaller than the R wave in RVH]

54
Q

With RVH, there is often associated ____ axis deviation

A

right

55
Q

What EKG changes occur with LVH?

A

QRS complexes have exaggerated amplitude (in height and depth), especially in the chest leads (V1-6)

S wave appears even deeper in V1 and there is a large R in V5

There is also left axis deviation

56
Q

What T wave changes might be present with LVH?

A

Often T wave inversion and asymmetry

Usually best to check on V5 or V6 (since these are over left ventricle); asymmetry because inverted T wave has gradual downslope and very steep return to baseline

57
Q

Ventricular strain is usually associated with ventricular hypertrophy, which displays on ECG as depression of the ____ segment

A

ST

58
Q

EKG changes with RVH

A

R waves prominent in V1, V2, with R:S ratio > 1

Deep S waves in V5,V6

Others: RAD + 90degrees+, incomplete RBBB, ST-T strain pattern in II, III, aVF, P pulmonale, S1 S2 S3 pattern (kids)

Cardiovascular Exam II (11 decks)

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