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Cardiovascular II Final Exam > AV blocks (Johnston) > Flashcards

AV blocks (Johnston) Flashcards

1
Q

AV block

A

-A block in the cardiac conduction system that causes disruption of atrial-to-ventricular electrical conduction

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2
Q

PR interval is

A

-from the ONSET of the P wave to end of P wave (just prior to upstroke of QRS complex)

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3
Q

Normal PR interval is

A

0.12-0.20 seconds

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4
Q

Characteristics of First degree AV block

A
  • P wave precedes QRS complex!!! but PR interval, although uniform is >0.2 sec
  • PR interval is fixed but prolonged (>0.2 sec)
  • Minor A-V conduction defect with delay at or below A-V node
  • PARTIAL block only

*(each small square is 0.04 seconds; each big square is 0.2 seconds so 1st degree AV block if PR >5 small boxes)

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5
Q

Etiology of 1st degree AV block

A
  • Atherosclerosis, HTN, Diabetes
  • Degeneration of conduction system/FIBROSIS congenital heart disease (CHD)
  • CAD–ischemia
  • Drugs
  • Endocrine
  • Infiltrative
  • Valvular calcification (mitral, aortic)
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6
Q

Drugs associated with 1st degree AV block

A
  • B-blocker
  • CCB
  • Digitalis
  • Antiarrhythmias (class I & III)
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7
Q

Endocrine disorders associated with 1st degree AV block

A
  • Hypothyroid
  • Hyperthyroid
  • Adrenal insufficiency
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8
Q

Inflammatory conditions associated with 1st degree AV block

A
  • RF
  • SLE
  • MCTD
  • Myocarditis
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9
Q

Infiltrative conditions associated with 1st degree AV block

A
  • Amyloidosis
  • Sarcoidosis
  • Hemochromatosis
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10
Q

Intermittent claudication means

A

-symptomatic discomfort/pain usually due to an atherosclerotic occlusive disease of vessels in lower extremityu

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11
Q

Low amplitude of QRS complex less than 5mm (low voltage QRS) indicates

A
  • Lung disease!
  • Obstructive lung disease-COPD, asthma, Pulmonary HTN
  • Hyperinflation of lungs, increased A-P diameter
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12
Q

Hypokalemia in EKG is seen as

A

-Prominent U waves, flattening of T wave

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13
Q

Hyperkalemia in EKG is seen as

A

-Peaked T waves, widened QRS complex, absence of P wave (with higher potassium levels)

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14
Q

Epigastric burning, belching diaphoresis can frequently be seen in

A
  • inferior or diaphragmatic surface of heart attacks
  • affects inferior wall of heart
  • characterized by heightened vagal tone–nausea, vomiting
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15
Q

Lightheadedness can be caused by

A

-Bradycardia

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16
Q

Symptomatic vs asymptomatic bradycardia treatment

A
  • Asymptomatic–leave alone

- Symtomatic = ATROPINE!!

17
Q

ST-T changes suggesting early ventricular depolarization symptoms

A

-usually asymptomatic!

18
Q

Inferior wall MI associated with what symptoms

A
  • HIEGHTENED VAGAL TONE–epigastric burning, GI manifestations
  • Bradycardia–highetened vagal tone slows down the heart
  • Diaphoresis
  • Levine’s sign–patient puts hand over sternum due to chest pain
19
Q

2 types of Second Degree AV block

A
  • Mobitz I (Wenckebach)

- Mobitz II

20
Q

Mobitz I (Weckebach) is characterized by

A
  • Progressive PR-interval prolongation Prior to Dropped QRS
  • “Grouped beats”
  • Progressing lengthening results from earlier arrival in relative refractory period of A-V conduction
  • Implies impairment of A-V conduction (A-V node)
  • Transient
  • Level of block is at level of AV node
  • Narrow QRS complex
21
Q

Etiology of Mobitz I

A
  • All things that cause 1st degree AV block
  • Digitalis toxicity
  • Ischemic events–INFERIOR MI!!!
  • Myocarditis
22
Q

Sequence of events seen in Mobitz I 2nd degree AV block

A
  • Progressive lengthening of PR interval with intermittent dropped beats:
    1) Good rapid cond. across AV node, normal PR interval
    2) Conduction less good, PR longer
    3) Conduction even worse; even longer PR interval
    4) Conduction fails so QRS is dropped
    5) AV node recovers so PR is normal again
23
Q

Acute inferior MI is associated with ST elevation in what leads??

A

-II, III and AVF

24
Q

Etiology of 2nd degree AV Block Mobitz Type II

A
  • Ischemic Heart disease
  • Maybe seen with acute ANTERIOR MI because block is DISTAL (below) TO AV NODE
  • Degeneration of conduction system
25
Q

Characteristics of 2nd degree Av Block Mobitz Type II

A
  • PR interval uniform
  • Dropped beat (QRS) bc P wave fails to conduct
  • Occurs at the level of: Bundle of His, Both Bundle branches, Fascicular branches (aka BELOW/DISTAL to AV node)
  • Progressive/Irreversible
  • WORSE prognosis than Mobitz Type I
26
Q

Name the disorder based on the following EKG findings:

  • AV block at the level of bundle of His or at bilateral bundle branches or trifascicular
  • PR intervals do NOT lengthen
  • Sudden dropped QRS without prior changes/lengthening
A

-Mobitz Type II Second Degree AV block (Non-Wenckebach)

27
Q

“High” vs “Low” AV block: site of block

A
  • High= Crest of AV node

- Low: Bundle of His, Bilateral bundle branch or trifascicular

28
Q

“High” vs “Low” AV block: Type of escape rhythm

A
  • High: Junctional escape rhythm, Narrow QRS, Adequate rate (40-55)
  • Low: Ventricular escape rhythm, Wide QRS, Inadequate rate (20-40); danger of systole or ventricular tachycardia
29
Q

“High” vs “Low” AV block: underlying pathology

A

High (assoc with mobitz I): Right CAD, diaphragmatic infarction, edema around AV node
Low (assoc with Mobitz II): LAD CAD, large anteroseptal infarction or chronic degeneration of conduction system

30
Q

“High” vs “Low” AV block: rhythm before complete block

A
  • High: preceded by Mobitz I (Wenckebach) 2nd degree AV block
  • Low: Preceded by Mobitz II 2nd degree AV block
31
Q

What do you see in a Left Bundle Branch block?

A

-Leads I, II, V5 and V6 look similar

32
Q

Third Degree Heart Block (complete heart block) characteristics

A
  • P waves NEVER related to QRS complexes
  • Two independent rhythms: (AV Dissociation)–no P waves conduct to ventricle
  • Can occur above OR blow AV node:
  • Above: Junctional rhythm (narrow QRS rate 40-55)
  • Below: Ventricular pacemaker, wide QRS (rate 20-40)
33
Q

Etiology of 3rd degree Heart Block

A
  • Ischemic
  • Infiltrative diseases
  • Cardiac surgery: by-pass, valve replacement, myocarditis, degenerative
34
Q

In a complete 3rd degree AV block, when the conduction of supra ventricular depolarizations to the ventricles is completely blocked, what happens?

A
  • An automaticity focus escapes to pace the ventricles at its inherent rate
  • Junctional focus: normal (narrow) QRS, ventricular rate 40-60
  • Ventricular focus: PVC like QRS, ventricular rate 20-40
35
Q

How do you treat a 3rd degree AV block

A

-Pacemaker!

36
Q

On every ECG, check

A
  • PR interval: increased consistently in 1st degree AV block, Progressively increases with Wenckebach, Totally variable in 3rd degree block, decreased in WPW and LGL syndromes
  • P without QRS response: Wenckebach and Mobitz II AV blocks; 3rd degree blocks=independent

Cardiovascular II Final Exam (13 decks)

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