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CP Exam 2 > DSA: Abnormal ECGs > Flashcards

DSA: Abnormal ECGs Flashcards

1
Q

What happens when the SA node fires?

A
  1. AP is distributed throughout the atria
  2. Sent to the AV node via the internodal pathway, where conduction is delayed–> ventricles are depolarized–> AP stops due to the cartilaginous rings.
  3. Repolarization occurs backwards
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2
Q

What is the purpose of the AV nodal delay?

A

Allows the atria to contract and pump all of the blood into the ventricles, before it begins to contract

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3
Q

In the ventricles, what is the first and last to depolarize?

A

1st to depolarize–> septum

Last to depolarize–> posterior aspect of the L heart

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4
Q

Why is the first ventricular myocyte to depolarize the last to repolarize?

A

The durations of the plateu phases of the AP are different.

The first ventricular myocyte has the longest plateau.

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5
Q

What lead gives us a good view of what is going on from L–> R in the heart, but a poor view of events moving up or down?

A

Lead 1

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6
Q

One of the limitations of either the augmented unipolar leads or the standard limb leads is that?

A

They all look at the heart from the same plane (the coronal, to use the anatomist’s term).

In order to view the heart from another plane (the transverse or horizontal plane), we use the six chest leads.

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7
Q

What occurs during the P wave?

A

SA nodal depolarization

Atrial depolarization

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8
Q

What occurs during the PR interval?

A

Depolarization from the SA node THROUGH the AV node via the internodal pathway.

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9
Q

What is the QT interval?

A

Total time the ventricles are contracted

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10
Q

What phase is QRS of ventricular AP?

A

Phase 0

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11
Q

What refractory period occurs during the ST segment?

A

Absolute refractory period.

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12
Q

At the end of the QRS complex, all ventricle myocytes are depolarized in phase ___ of the AP.

A

2

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13
Q

What should we remember about how the T-wave relates to the QRS complex?

A

They often head in the same direction within 1 lead, despite their electrical events being opposite of one another.

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14
Q

QT interval time

A

.35 seconds

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15
Q

R-R interval time

A

Use to find HR

-0.6seconds to 1 second

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16
Q

time in 1 little square

1 box

A

times in 1 little square= 0.04s

1 box= 0.2s

17
Q

The mean electrical axis tells us what?

A

the net direction the depolarization or repolarization is heading.

18
Q

______ degrees - meaning that the net depolarization is heading almost straight down towards the apex of the heart

A

Around 85 degrees

19
Q

Pt has a L ventricular hypertrophy but a normal conduction pathway. What will this do to the ECG?

A

Increase the amplitude (height) of the QRS

20
Q

What does normal sinus rhythm mean?

A

SA node is driving the heart

21
Q

What is sinus tachycardia?

How will this affect the ECG?

A

SA node is driving the heart, but at a faster rate than normal (>100 bp/min).

-PR interval may be shorter than normal

-QRS interval may be shorter than normal

22
Q

Sinus Bradycardia is the result of a what?

What do we see on the ECG?

A

Long phase 4 in the pacemaker cells of the SA node.

Prolonged PR interval and QT interval.

23
Q

In sinus bradycardia, the heart rate may get so slow, that what may happen?

A

Another pacemaker takes over.

24
Q

What is a flutter?

Fibrillation?

A

Flutter- depolarization tavels around the around, but does not stop; producing a high-rate weaker than normal contraction.

If we see chaos (same path is not taken every time), we see fibrillation. Heart cannot pump even though it is still depolarizing.

25
Q

What is this?

A

A fib

  • No P waves
  • QRS and T waves are normal
  • QRS complex are irregularly irregular
26
Q

What prevents a A-fib from becoming a V-fib?

A

Slow conduction time of the AV node

27
Q

What is this?

A

V-fib

Ventricular flutter becomes v-fib.

28
Q

In V-fib, the most dangerous PVC occurs where on ECG?

Why?

A

T wave

  • During the T wave, part of the ventricular myocardium is depolarized (in absolute refractory period) while the other parts are repolarized (not in absolute refractory period).

By the time the depolarization travels around the heart, the muscle that was refractory has now repolarized and is ready to conduct the depolarization - so the depolarization just keeps going around the heart.

29
Q

SA nodal block is defined as a failure of the cardiac action potential to emerge from the SA node. How ?

How will this look on the ECG?

A

-Pacemaker cells of the SA node work, but the AP cannot be spread from the SA node.

-A flat line (whole thing is flat).

Luckily, SA nodal block is intermittent and lasts only a beat or two. IF perm, you need a pacemaker

30
Q

What is this?

A

First degree AV blockà AV nodal depolarization is slower than normal, but that every impulse generated by the SA node does get through to the ventricles.

Only differences:

Rate and rhythm are normal, but the PR interval is prolonged beyond the normal upper limit of 0.21 seconds.

31
Q

What is this?

A

AV node is damaged so it remains refractory and unable to conduct an action potential for a much longer time than normal.

  1. Thus, ventricular depolarization occurs intermittingly, causing losses of QRS waves in the reading. So, not every P wave is followed by a QRS complex.
32
Q

What are the two types of 2nd degree AV nodal block?

A

1. Mobitz I block (Wenckebach)

2. Mobitz II block

33
Q

Mobitz II block?

A

AV node refractory period is so long that AV node cannot conduct on a regular bassis.

AV nodal depolarization fails intermittingly, causing losses of QRS waves in the reading.

AV block is that not every P wave is followed by a QRS complex.

34
Q

Mobitz I block?

A

PR interval gradually increases until the QRS segment is dropped.

Cycle resumes on next beat.

35
Q

QRS complex of the 2nd AV nodal blocks are a result of what?

A

QRS complexes that occur are the result of the depolarization initiated by the SA node.

36
Q

What is this?

A

Third degree AV block- AV node does not conduct depolarization from the atria–> ventricles. SA node will fire and depolarize atria,But the AV node does not conduct the AP at all. Thus, the ventricles are not depolarized. However, our backup pacemakers such as bundle branches or BoH will depolarize them

  • complete dissociation of P and QRS wave
  • atrial rate of 120 b/min and a ventricular rate of 45 b/min)
  • P waves occur virtually on top of QRS complex
37
Q

If bundle of His takes over in third degree AV nodal block, what happens to the QRS complex?

A

look normal

  • rate of 30-40 min–> junctional rhythm

CP Exam 2 (27 decks)

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