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ECG > Underlying Rhythms > Flashcards

Underlying Rhythms Flashcards

1
Q

Describe Sinus Rhythm?

A

P-waves: Present and Upright
Rate: 60-100bpm
Rhythm: Regular

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2
Q

Describe Sinus Tachycardia?

A

P-waves: Present and Upright

Rhythm: Regular

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3
Q

Describe Sinus Bradycardia?

A

P-waves: Present & Upright
Rate: <60bpm
Rhythm: Regular

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4
Q

Describe Sinus Arrhythmia?

A

P-waves: Present and Upright
Rate: 60-100bpm
Rhythm: Irregular

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5
Q

Describe Sinus Pause?

A

Failure of Atria to depolarize
Impulse is formed but blocked in Atria
Usually for 1-2 beats (Sinus node does not reset)

Pause in rhythm no longer than 2 beats

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6
Q

Describe Sinus Arrest?

A

Failure in Automaticity of SA node
Generally greater than 2 cycle lengths
Failure of SA node to create impulse
SA node rhythm needs to reset

Pause in rhythm longer than 2 beats and SA node reset

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7
Q

Describe Junctional Rhythm?

A

P-waves: Absent (or inverted)
Rate: 40-60bpm
Rhythm: Regular

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8
Q

Describe Accelerated Junctional Rhythm?

A

P-waves: Absent (or inverted)
Rate: 60-99bpm
Rhythm: Regular

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9
Q

Describe Junctional Tachycardia?

A

P-waves: Absent (or inverted)
Rate: 100-130bpm
Rhythm: Regular

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10
Q

Describe Supraventricular Tachycardia?

A

A run of three or more supraventricular ectopics
P-waves: Absent
Rate: 140-250bpm
Rhythm: Regular

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11
Q

Describe Atrial Flutter?

A

P-waves: Absent - replaced by saw tooth flutter waves
Rate: Atrial - 250-400bpm
Ventricular - 60-100bpm
Rhythm: Regular

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12
Q

Describe Atrial Fibrillation?

A

Rapid Chaotic Atrial Depolarisation
P-waves: Absent - replaced by erratic fibrillatory waves
Rate: Atrial = >400bpm (excessively fast)
Ventricular = 60-100bpm
Rhythm: Irregular

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13
Q

Describe Wandering Atrial Pacemaker?

A

P-waves: Present - changing morphologies
Rate: 60-100bpm
Rhythm: Regular

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14
Q

Describe Idioventricular Rhythm?

A

Also known as “Ventricular Escape Rhythm”
P-waves: may be absent (if present, there is AV dissociation)
Rate: <40bpm
Rhythm: Regular
QRS: Wide and Bizarre (>0.12secs)

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15
Q

Describe Ventricular Arrhythmias?

A

Based on Pacemakers of Heart
SA node (Sinus Rhythm - 60-180bpm)
AV node (Junctional Rhythm - 40-60bpm)
Below AV node (Idioventricular Rhythm - <40bpm)

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16
Q

Describe Ventricular Ectopics?

A

A premature beat arising from an escape pacemaker in the ventricles (specifically in the bundle branches, Purkinje network or ventricular myocardium)

The QRS is wide, bizarre and early, generally followed by a full compensatory pause before the next sinus beat (SA node is not reset)

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17
Q

What is Unifocal Ventricular Ectopic?

A

Ventricular Ectopic arise from the same focus within the ventricles
Same morphology

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18
Q

What is Multifocal Ventricular Ectopic?

A

Ventricular Ectopics arise from different foci within the ventricles
Different Morphologies

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19
Q

What is Interpolated Ventricular Ectopic?

A

Occurs between sinus beats without a compensatory pause (no pause seen)
It does not affect underlying rhythm
It is sandwiched between sinus beats

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20
Q

What is Bigeminy Ventricular Ectopic?

A

Pattern occurs where every 2nd beat is ventricular ectopic (need to determine whether unifocal/multifocal)

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21
Q

What is Trigeminy Ventricular Ectopic?

A

Pattern occurs where every 3rd beat is ventricular ectopic (need to determine whether unifocal/multifocal)

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22
Q

What is a coupled Ventricular Ectopic?

A

Two Ventricular Ectopics in a row

need to determine whether unifocal/multifocal

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23
Q

What is a triplet Ventricular Ectopic?

A

Three ventricular ectopics in a row

need to determine whether unifocal/multifocal

24
Q

Explain Ventricular Tachycardia?

A

Originates in an ectopic pacemaker in the ventricles

It is a run of three or more ventricular ectopics

25
Q

Explain Features Suggestive of Ventricular Tachycardia?

A

AV dissociation
Presence of Fusion/Capture Beats

When there is a positive complex in V1:

  • Monophasic/Biphasic complex in V1
  • An RS pattern in V6 with deeper S-wave

When the QRS pattern is more negative in V1

  • A wide R wave in V1/V2
  • A slurred/notched s-wave downstroke in V1/V2
26
Q

Explain R on T Phenomenon?

A

When a ventricular ectopic occurs during the relative refractory period of ventricular repolarization (peak of T-wave)
R on T occurs on the peak of the T-wave of the preceding beat. (looks like an early ectopic beat on T-wave)

27
Q

Explain “Torsades de Pointes”?

A

“Twisting around a Point” - twisting around the isoelectric line
It is a form of polymorphic ventricular tachycardia and characterized by changing amplitude of QRS complexes

28
Q

What is Ventricular Fibrillation?

A

Ventricles do not beat but twitch rapidly asynchronously and ineffectively - no discernable QRS complex
Cardiac output ceases which cause patient to lose consciousness

29
Q

What is Ventricular Asystole/Standstill?

A 
Absence of ventricular electrical activity
P-waves: May be present
Rate: generally 60-100bpm (atrial)
Rhythm: Regular/Irregular
QRS: Absent
30
Q

What is an Ectopic Beat?

A

A beat that appears early before the next normal beat is due
They can arise from a site in the:
- Atria or AV junction (Supraventricular Ectopic)
- Ventricles (Ventricular Ectopic)

They can occur as; Isolated, Repetitive, Runs, Bigeminy or Trigeminy

31
Q

Explain Supraventricular Ectopic Beats?

A

Premature beats that arise from a site in the atria or the AV junction before the next normal beat is due

  • Atrial depolarization will occur via an abnormal pathway, which causes a change in the p-wave
  • Ventricular depolarization occurs normally (AV node-Bundle of His-BB-etc.) producing a normal QRS complex

They can occur as; Isolated, Repetitive, Runs, Bigeminy or Trigeminy

32
Q

What is a Supraventricular Ectopic arising from a site in the atrial region called?

A

Premature Atrial Contraction (PAC)

33
Q

What is a Supraventricular Ectopic arising from a focus in the AV junction called?

A

Premature Junctional Contraction (PJC)

34
Q

Describe how you can tell if the ECG has a junctional rhythm?

A

It has an inverted P-wave

35
Q

Explain the concept Compensatory Pause?

A

It is the RR interval following a premature contraction
There are two types of pauses: Full or Incomplete

Full Compensatory Pause (Ventricular Ectopic) - SA node does not depolarize (does not reset the timing of the SA node) by a premature contraction. The beat occurs early and the next beat occurs where it should have been - back in line with the next beat

Incomplete Compensatory Pause (Supraventricular Ectopic) - SA node is depolarized (which resets the timing of the SA node). The beat occurs early and the next beat occurs early too (earlier than it used to be) because the SA node has completely reset and now has a new timing path

36
Q

What is Supraventricular Tachycardia?

A

A run of 3 or more supraventricular ectopics

P-wave: Absent (may be present in previous T-wave)
Rate: 140-250bpm
Rhythm: Regular

37
Q

Explain the Re-entry mechanism?

A

Process by which a fast rhythm is self-propagated. A closed circuit of electrical impulses is created. This circuit is usually started and stopped by an outside stimulus (Ectopic Beat)

38
Q

What are the 3 essential properties that must exist for re-entry to occur?

A
  • 2 conducting Pathways with a proximal and distal connection
  • One pathway - fast conduction velocity while the other - slow conduction velocity
  • Fast pathway has a longer refractory period while the slow pathway has a shorter refractory period
39
Q

What is a Ventricular Tachycardia Fusion Beat?

A
  • A supraventricular beat and a ventricular impulse coincide to produce a hybrid beat: 2 foci of pacemaker cells firing simultaneously (SA node & source of ventricular ectopics)
  • Produces an immediate width and morphology QRS complex to the supraventricular and ventricular complexes
40
Q

What is a Ventricular Tachycardia Capture Beat?

A

The SA node transiently captures the ventricles (normal QRS width)

41
Q

What does the presence of a Fusion or Capture beat imply?

A

Provides evidence that the tachycardia is most likely ventricular in origin and not supraventricular tachycardia with aberrant ventricular conduction

42
Q

What does Electromechanical Dissociation (EMD) or Pulseless Electrical Activity (PEA) mean?

A

Refers to any heart rhythm observed on an ECG that should be producing a pulse but isn’t.

Failure of electromechanical coupling (normally electrical activation of muscle cells precedes mechanical contraction of the heart)

In PEA there is electrical activity, but the heart either, does not contract or there are other reasons why there is insufficient cardiac output to generate a pulse

43
Q

What is an Atrioventricular Block?

A

An impulse that fails to be conducted (or is delayed) from the atria to the ventricles
The types of AV blocks are divided into 3 categories:
- First, Second and Third Degree Blocks

The higher the level of block = higher level of concern
To assess this, we measure the PR interval

44
Q

What is the First Degree AV Block?

A

The PR interval is constant but >0.2 secs
Every P-wave is followed by an R-wave (long interval)

Indicates a partial block

45
Q

What is a Second Degree Mobitz Type 1 Block (Wenckebach)?

A

The PR interval progressively lengthens until conduction falls and a QRS complex is dropped

46
Q

What is a Second Degree Mobitz Type 2 Block?

A

The PR interval remains constant but eventually drops a QRS complex

Rhythm: produces a conduction ratio of 4:3 or 3:2 (atrial to ventricular complexes)
QRS: Wide due to bundle branch block

Indicates a block at either the Bundle of His, or bilateral bundle branches, or tri-fascicular.

47
Q

What is the Second Degree (2:1) Block and High Degree Block?

A

An Arrhythmia which is caused by an absence of conduction of impulses through the AV node and/or bundle branches

Ventricular Rate < Atrial Rate
Becuase of a bundle branch block the QRS complexes may be normal/abnormal

Second Degree AV (2:1) Block
- has to have 2 P-waves to 1 QRS throughout the entire ECG strip

High-Degree AV Block
- has to have >3 P-waves to 1 QRS throughout the entire ECG strip

48
Q

What is a Third Degree AV Block?

A

The PR interval progressively lengthens but a QRS complex is NEVER dropped

Impulses from the SA node are never conducted through the AV node. The atrial and ventricular rhythms are regular however, there is no connection between the two.

Atria are paced by the SA node - impulse is blocked at AV node - pacemaker site below AV node activates the ventricles (escape pacemaker)

49
Q

What are the two types of Third Degree (Complete) AV block?

A

Transient and Permanent

Transient - usually associated with junctional escape rhythm (QRS complexes are narrow - 45-60bpm). Caused by blocking of impulse through AV node

Permanent - usually associated with ventricular escape rhythm (QRS complexes are broad - 30-40bpm). Caused by blocking of impulses through both bundle branches

50
Q

Describe a Bundle Branch Block?

A

Bundle branch block is a condition in which there’s a delay or obstruction along the pathway that electrical impulses travel to make your heart beat. The delay or blockage may occur on the pathway that sends electrical impulses to the left or the right side of the bottom chambers (ventricles) of your heart.

51
Q

Describe the difference between the Right Bundle Branch and the Left Bundle Branch?

A

RBB - One main branch of the right side of the interventricular septum to the right ventricle

LBB - Has main stem which divides into 2 parts (anterior - long and thin; posterior - short and thick) on the left side of the interventricular septum to the left ventricle

52
Q

Explain how to determine a Right Bundle Branch Block (RBBB)?

A

A block to the right bundle branch which impulse are prevented from entering right ventricle

QRS: measure width (V1/V2) >0.12 secs wide
QRS Axis: Normal or Deviated to Right

V1-V2: rSR’ complex with a broad R-wave (M or rabbit ears); T-wave inversion may be present
V5-V6: QRS complex with deep and slurred S wave

53
Q

Explain how to determine a Left Bundle Branch Block (LBBB)?

A

A block to the left bundle branch which impulses are prevented from entering left ventricle

QRS: measure width (V1/V2) >0.12 secs wide
QRS Axis: Normal or Deviated to Left

V1-V2: deep, wide S-waves producing typical rS or QS complex
V5-V6: tall, wide RS complex, may be notched at peak; T-wave inversion may be present

54
Q

Describe a Left Anterior Fascicular Block (Hemiblock)?

A

Impulses are prevented from entering the anterior and lateral walls of the left ventricle.
Impulses travel down left posterior fascicle and into interventricular septum and posterior wall of left ventricle, then into anterior and lateral walls of left ventricle

Depolarization occurs:

  1. Septum - left to right
  2. Right Ventricle - right to left
  3. Left Ventricle - right to left (posterior wall first, followed by anterior and lateral walls)
55
Q

Describe a Left Posterior Fascicular Block (Hemiblock)?

A

Impulses prevented from entering the interventricular septum and posterior wall of the left ventricle.
Impulses travel down the left anterior fascicle into anterior and lateral walls of left ventricle and then into the posterior wall of the left ventricle.

Depolarization occurs:

  1. Septum - right to left
  2. Right Ventricle - left to right
  3. Left Ventricle - left to right (anterior and lateral walls first, followed by the posterior wall)

ECG (4 decks)

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