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_MS2 Cardio > 8/4- Electrocardiography at the Bedside 1 > Flashcards

8/4- Electrocardiography at the Bedside 1 Flashcards

1
Q

What is the PR interval?

A

Segment from P wave from BEGINNING of the QRS complex (not R wave itself)

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2
Q

1 mm on the EKG corresponds to what?

A

1 mm = 40 ms (0.04 s) = small box

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3
Q

5 mm on the EKG corresponds to what?

A

5 mm = 200 ms (0.20 s) = large box

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4
Q

Normal P-R interval = length?

A

Normal P-R interval = 3-5 small boxes = 120-200 ms

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5
Q

Normal QRS interval = length?

A

Normal QRS interval = 2-3 small boxes = 80-120 ms

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6
Q

Normal QTc interval = length?

A

Normal QTc interval = 9-11 small boxes = 360-440 ms (400 +/- 40)

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7
Q

What does QTc refer to?

A

Corrected QT interval (corrected for heart rate)

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8
Q

Systematic Evaluation of 12 lead ECG (11)?

A
  1. Rhythm
  2. Rate
  3. QRS axis
  4. P wave morphology
  5. P-R interval
  6. QRS interval
  7. QT interval
  8. Chamber enlargement: LVH, RVH
  9. Pathologic Q waves
  10. ST and T wave changes
  11. Precordial R wave progression
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9
Q

What is the range of normal sinus rhythm?

A

60-100 per minute

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10
Q

What is the R-R interval?

A

Interval between 2 consecutive QRS complexes

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11
Q

What type of rhythm is shown here? Characteristics?

A

Atrial fibrillation (until proven otherwise)

  • No P wave
  • Rhythm is irregular
  • Present QRS complexes
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12
Q

Heart rate assessment?

A

Divide 300 by the R-R interval expressed in number of “large boxes”

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13
Q

If the R-R interval is 400 ms or 2 “large boxes”, what is the heart rate?

A

HR = 300/2 = 150 bpm

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14
Q

P wave is usually positive in what leads?

A

P wave is usually positive in all ECG leads except aVR and V1

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15
Q

P wave results from what?

A

Early RA and late LA depolarization

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16
Q

Abnormal P waves are indicative of what?

A
  1. LA enlargement: bifid P wave “P-mitrale” due to delayed left atrial depolarization
  2. RA enlargement: tall P wave > 2.5mm
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17
Q

Best lead to assess P wave is what?

A

Lead II or III/aVF

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18
Q

What is this? What causes it?

A

Bifid or notched P wave in lead II

  • Takes longer to fully depolarize the L atrium (delayed portion of P wave is due to longer LA depolarization)
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19
Q

What is this? What does it indicate?

A

Tall P wave > 2.5 mm in lead II

  • Right atrial enlargment
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20
Q

What constitutes a prolonged PR interval? What causes it?

A

PR > 0.20s

  • Block in the AV node delays AV conductions
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21
Q

What are some of the causes of PR elongation? (broadly, 3)

A

Acquired “reversible” causes

  • Drugs
  • Acute ischemia or infarction

“Irreversible” causes

  • Degenerative or calcific disease of the conduction system (“irreversible”) called Lev’s or Lenegre’s disease
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22
Q

What drugs specifically may cause PR elongation?

A
  • Beta blockers
  • Ca channel blockers
  • Digoxin
  • Amiodarone
  • Clonidine
23
Q

What is Wolf-Parkinson Syndrome?

A

ECG Triad:

1. Short P-R interval (< 120 ms)

2. Delta wave: an abnormal extra + wave immediately before the QRS complex; slurred initial QRS upstroke

3. Wide QRS complex > 120 ms

Restated:

Syndrome associated with accessory bypass tract (bypassing AV node) which shortens the PR interval

  • Also characterized by wide QRS complex (QRS > 0.12) and delta waves (pic s)
24
Q

What happens to the QRS complex in BBB (bundle branch block)?

A

QRS complex will have early R wave and one late R’ wave, also called an RSR’ complex

  • Will also be widened

((- An initial negative inflection of the QRS complex is the Q wave

  • The first positive inflection of the QRS complex is the R wave
  • The first negative inflection of the QRS complex is the S wave))
25
Q

What is the key difference between R and L BBB?

A

Location of RSR’

RBBB: RSR’ in V1 or V2

LBBB: RSR’ in V5 or V6

26
Q

What does a widened QRS complex with RSR’ show?

A

Bundle branch block (or dilation of the corresponding chamber)

(normal QRS = 80-120 ms = 2-3 small boxes)

27
Q

What heart chamber is located closest to chest wall?

A

Right ventricle

28
Q

What is this?

A

RSR’ in chest lead V1

29
Q

What is this?

A

RSR’ in chest lead V2

30
Q

What do these together indicate?

A

RSR’ in chest leads V1 and V2 (placed over RV chamber) indicating RBBB

31
Q

What is this?

A

RSR’ in chest lead V5

32
Q

What is this?

A

RSR’ in chest lead V6

33
Q

What do these together indicate?

A

RSR’ in chest leads V5 or V6 (placed over LV apex) indicating LBBB

34
Q

What causes bundle branch block?

A
  • Ischemia or infarction of the bundle branch
  • Eccentric hypertrophy of the ventricles
35
Q

QT changes with what?

A

Heart rate

36
Q

What is QTc? Normal value?

A

QT corrected for heart rate

  • Varies from 360-440 ms
37
Q

How do ewe calculate QTc?

A

Divide QT by square root of R-R interval

38
Q

What causes prolonged QT interval (acquired)?

A

Drugs

  • Anti-arrhythmics (class IA, IC, III)
  • Anti-psychotic phenothizines
  • Tricyclic antidepressants
  • Antifungals

Electrolyte abnormalities: low K, Mg, or Ca (low K is the most common)

39
Q

What causes prolonged QT interval (congenital)?

A
  • Jervell and Romano Ward
40
Q

What is this?

A

Torsades de Pointes

  • (polymorphic ventricular tachycardia)
  • Classic complication of Long QT syndrome
41
Q

What does RAE (right atrial enlargement) cause?

A

Prominent early portion of P > 2.5

42
Q

What does LAE (left atrial enlargement) cause?

A

Delayed late portion of P with a bifid P in II

43
Q

What will be seen with RBBB? Which leads?

A

RSR in V1/V2

44
Q

What will be seen with LBBB? Which leads?

A

RSR’ in V5/V6

45
Q

What is normal QTc?

A

360-440

46
Q

What can long QT lead to?

A

TDP VT (Torsades de Pointes)

47
Q

What is WPW?

A

Syndrome associated with accessory bypass tract (bypassing AV node) which shortens the PR interval

  • Also characterized by wide QRS complex (QRS > 0.12) and delta waves
48
Q

What may cause long PR?

A
  • Drugs (digoxin, BB, CCB)
  • Ischemia or infarction
  • Degeneration or calcification of AVN or His bundle
49
Q

What may cause long QT?

A
  • Drugs
  • Electrolytes (low K, low Ca, low Mg)
50
Q

Depolarization of the R atrium occurs in which part of the P wave?

A. Early

B. Late

C. Neither

A

Depolarization of the R atrium occurs in which part of the P wave?

A. Early

B. Late

C. Neither

51
Q

Why is the R atrium depolarized earlier tan the L atrium?

A. Sinus node is int he L atrium

B. Sinus node is in the R atrium

C. AV node is closest to the R atrium

D. AV node is closest to the L atrium

A

Why is the R atrium depolarized earlier tan the L atrium?

A. Sinus node is int he L atrium

B. Sinus node is in the R atrium

C. AV node is closest to the R atrium

D. AV node is closest to the L atrium

52
Q

All of the following drugs prolong the P-R interval except?

A. Beta blockers

B. Amiodarone

C. Ca channel blockers

D. Digoxin

E. Nitroglycerin

A

All of the following drugs prolong the P-R interval except?

A. Beta blockers

B. Amiodarone

C. Ca channel blockers

D. Digoxin

E. Nitroglycerin

Nitrates in general have no effect on AV conduction

53
Q

Bundle branch block is characterized by all of the following except:

A. QRS interval > 120 ms

B. QRS interval smaller than 120 ms

C. RSR’ QRS in some chest leads

D. Delay in ventricular depolarization

A

Bundle branch block is characterized by all of the following except:

A. QRS interval > 120 ms

B. QRS interval smaller than 120 ms

C. RSR’ QRS in some chest leads

D. Delay in ventricular depolarization

54
Q

WPW is characterized by all of the following except:

A. QRS interval > 120 ms

B. QRS interval smaller than 120 ms

C. Delta wave

D. Slurred initial upstroke of QRS

E. Accessory tract bypassing the AV node

A

WPW is characterized by all of the following except:

A. QRS interval > 120 ms

B. QRS interval smaller than 120 ms

C. Delta wave

D. Slurred initial upstroke of QRS

E. Accessory tract bypassing the AV node

_MS2 Cardio (35 decks)

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