Lecture 3/4 (Arrhythmias)

Question 1

Ectopic pacemakers:

Answer 1

• pacemakers cells in the atrium that are not SA nodal.
• lead to premature atrial contraction.

Question 2

What causes sinus tachycardia or sinus bradycardia?

Answer 2

• rate of SA nodal firing is increased or delayed.
  
  1. SNS/PSNS input.
  2. HCN channels (slow depolarization of pacemaker).

Question 3

What arrythmia is this?

Answer 3

• Sinus tachycardia.
  
  • Sinus rhythm (PQRST; only one P per QRS).
  • HR > 100.

Question 4

What arrythmia is this?

Answer 4

• Sinus bradycardia.
  
  • Sinus rhythm (PQRST; only one P per QRS).
  • HR < 60.

Question 5

What kind of rhythm is this?

Answer 5

• normal sinus rhythm
  
  • Sinus rhythm (PQRST; only one P per QRS).
  • HR between 60-100

Question 6

Primary heart block cause and ECG manifestation:

Answer 6

• Cause: delayed conduction through AV node or bundle of His.
• ECG: increased/lengthened PR interval.

Question 7

What arrythmia is this?

Answer 7

• Primary heart block.
• note increased PR interval.

Question 8

Secondary heart block cause and ECG manifestation:

Answer 8

• Cause: increased AV nodal refractory time; Not every atrial impulse is conducted through the AV node, His-Purkinje.
• ECG: more than one P wave per QRS complex.

Question 9

What kind of arrythmia is this?

Answer 9

• Secondary heart block.
• >1 P wave per QRS complex.

Question 10

Tertiary (complete) heart block cause and ECG manifestation:

Answer 10

• Cause: Atrial impulses are not conducted through AV node.
  
  • Atria beat at one rate and rhythm and ventricles beat at another.
  • Ventricular contraction is driven by escape rhythm.
• ECG: P and QRS waves at regular intervals, but not coordinated.

Question 11

What drives ventricular depolarization in tertiary (complete) heart block?

Answer 11

• escape rhythm.
• pacemaker cells in either AV node, bundle of his, or in ventricuar myocardium itself.

Question 12

The three pacemakers of the heart:

Answer 12

1. SA node.
   
   • Normal rate.
2. AV junctional.
   
   • Moderate rate.
3. Ventricular (his, purkinje, myocardium itself).
   
   • Very slow rate - not sustainable.

Question 13

Normal sequence of electrical conduction through myocytes:

Answer 13

1. Impulse travels unidirectionally in direction of excitable myocytes.
   
   • Refractory myocytes behind impulse prevent immediate reexcitation.
2. Impulse can only either:
   
   • continue forward or
   • collide with itself and extinguish.

Question 14

An ectopic pacemaker is:

Answer 14

• any pacemaker that forms in the heart outside of the SA node.

Question 15

Steps in formation of a reentry loop/circus rhythm:

Answer 15

1. Impulse reaches healthy and damaged cells.
2. Damaged cells only allow retrograde conduction, not anterograde.
3. Anterograde conduction through healthy cells.
4. Retrograde conduction through damaged cells.
5. Time for retrograde conduction longer than effective refractory period of previously excited healthy cells.
6. Healthy cells re-excited by retrograde conduction through damaged cells.
7. Reentry loop/circus rhythm formed.

Question 16

How does a reentry loop/ectopic pacemaker lead to the formation of an ectopic pacemaker?

Answer 16

• circus rhythm created by reentry loop exits reentrant loop and depolarizes
  adjacent myocardium and spreads.
• APs and contractions become uncoordinated, fibrillation can result.

Question 17

When does relative refraction of the fast Na+ channels involved in plateau potentials and myocardium depolarization occur on an ECG?

Answer 17

• mid-end T wave.
• cell may be prematurely depolarized by rogue circus rhythm during relative refraction.

Question 18

What causes atrial fibrillation?

Answer 18

• circus rhythm (formed from reentry loop) occurs in the atria and spreads.
• atrial myocardium depolarize and contract randomly.
• fibrillation results.

Question 19

Atrial fibrillation ECG manifestation (2):

Answer 19

• No P waves.
• Irregularly irregular rhythm.

Question 20

What arrhythmia is this?

Answer 20

A-Fib

• no P waves
• Irregularly irregular

Question 21

Why does the ventricular depolarization rate remain relatively low in comparison to atrial depolarization rate in atrial fibrillation?

Answer 21

• AV nodal delay.
• AV node pacemaker cells experience refraction, and so all atrial impulses are not relayed through the AV node to the ventricles.

Question 22

Atrial flutter ECG manifestation (4):

Answer 22

1. Sawtooth appearance.
2. rapid and regular P waves.
3. P waves before QRS.
4. >1 P wave per QRS.

Question 23

Primary difference between A-Fib and atrial flutter:

Answer 23

• Atrial flutter has:
  
  • P waves (>1 per QRS).
  • rapid and regular rhythm (PQRS).
  • slower rate.

Question 24

What arrhythmia is this?

Answer 24

Atrial flutter w/ 2:1 ventricular response

(2 P waves per QRS)

Question 25

What kind of arrhythmia is this?

Answer 25

Atrial flutter w/ variable ventricular response

Question 26

Cause of ventricular fibrillation:

Answer 26

* Ectopic pacemaker forms in ventricle and stimulates ventricular myocytes in relative refraction (downslope of T wave) to depolarize. * Ventricle does not contract simultaneously, it just quivers. * Cardiac ventricular output decreases / does not occur.

Question 27

What type of arrhythmia is this?

Answer 27

1. Normal rhythm 2. Event occurs 3. Ventricular tachycardia 4. Ventricular fibrillation

Question 28

Cause of ventricular tachycardia:

Answer 28

* Scarred/injured myocardium allows reentrant phenomoenon. * Ectopic pacemaker forms in the ventricles fires at a very high rate causing ventricles to enter tachycardia. * 300 BPM

Question 29

Cardiac output is impaired in V-Tach because:

Answer 29

* there is not enough time between ventricular contractions to allow for diastole.

Question 30

There are no P waves in V-tach or any other waves besides QRS because:

Answer 30

* they are masked by the sheer size of ventricular depolarization. * they are still occurring.

Question 31

What arrhythmia is this?

Answer 31

V-Tach * regular and rapid * wide QRS

Question 32

Cause of bundle branch block:

Answer 32

* Delayed/blocked conduction within a right or left bundle branch. * Conductance relayed from the unaffected ventricle to impaired side via interventricular septum myocytes (SLOW). * Widened QRS.

Question 33

What causes the wide QRS complex on bundle branch block ECGs?

Answer 33

* Delayed/blocked conduction within a bundle branch. * Conductance relayed from the unaffected ventricle to impaired side via interventricular septum myocytes, which have slow conduction rates. * Ventricular depolarization is longer, widened QRS complex.

Question 34

Right BBB ECG manifestation:

Answer 34

widened QRS on lead III, V1 and V2.

Question 35

Left BBB ECG manifestation:

Answer 35

widened QRS on lead I, lead II, and V5 and V6.

Question 36

What arrhythmia is this?

Answer 36

BBB widened QRS

Question 37

What arrhythmia is this?

Answer 37

BBB widened QRS

Question 38

Split R waves on an ECG (see image) are indicative of what type of arrhythmia?

Answer 38

BBB

Question 39

What type of arrhythmia is this?

Answer 39

right BBB * **Split R waves** * **Lengthened QRS complex** * **V1 and V2 analyze right ventricle**

Question 40

Premature ventricular contractions (PVCs) are: (include ECG manifestation)

Answer 40

* rogue ventricular contractions that arise from ectopic pacemaker in ventricle. * Widened QRS complex; no P waves associated with QRS complexes.

Question 41

What kind of arrhythmia is this?

Answer 41

premature ventricular contractions * widened QRS * no P wave * random QRS complexes