Clinical treatment of Arrhythmias

Question 1

Describe initiation of the cardiac cycle “P wave”

Answer 1

Initiation of the cardiac cycle normally begins with initiation of the impulse at the sinoatrial (SA) node.
A resulting wave of depolarization passes through the right and left atria, which produces the P wave on the surface ECG and stimulates atrial contraction.

Question 2

Describe the physiology of what happens after the P wave

Answer 2

Following activation of the atria, the impulse proceeds to the atrioventricular (AV) node, which is the only normal conduction pathway between the atria and the ventricles.
The AV node slows impulse conduction which allows time for contraction of the atria and the pumping of blood from the atria to the ventricles prior to ventricular contraction.
Conduction time through the AV node accounts for most of the duration of the PR interval.

Question 3

Which part of the PQRST beats is the impulse passing through the bundle of His?

Answer 3

Just below the AV node, the impulse passes through the bundle of His. A small portion of the last part of the PR interval is represented by the conduction time through the bundle of His.

Question 4

Which part of the PQRST beats is the impulse passing through the bundle branches?

Answer 4

After the impulse passes through the bundle of His, it proceeds through the left and right bundle branches. A small portion of the last part of the PR interval is represented by the conduction time through the bundle branches.

Question 5

What occurs during the QRS complex?

Answer 5

Atrial repolarization and relaxation

Question 6

The T wave on the ECG represents the _____________

Answer 6

repolarization and relaxation of the ventricles.

Question 7

Arrhythmias fall into two categories… _____ and ____

Answer 7

Either your rhythm is too slow or too fast.

Bradyarrhythmias and Tachyarrhythmias

Question 8

Where in the conduction system can problems develop?

Answer 8

Sinus node
AV node
Below the AV node

Question 9

Conditions that are examples of – sinus node dysfunction

Answer 9

• sinus bradycardia
• sinus arrest/pause
• tachy-brady syndrome
• chronotropic incompetence- inability to
  mount age-appropriate HR with exercise

Question 10

Where in the conduction system can problems of bradyarrhythmias develop?

Answer 10

1) SA node
2) AV node
- first degree AV block
- Mobitz I 2nd degree AV block (Wenkebach)
3) below the AV node (infranodal/His Purkinje system)
- Mobitz II 2nd degree AV block
- complete heart block

Question 11

First-Degree AV Block

• AV conduction?
• PR interval?

Answer 11

AV conduction is delayed, and the PR interval is prolonged (> 200 ms or .2 seconds)

First-degree AV block can be thought of as a delay in AV conduction, but each atrial signal is conducted to the ventricles (1:1 ratio)!! Between P wave and QRS interval

Question 12

Third degree heart block AKA

Answer 12

Complete Heart block

*complete dissoc. betwen waves thorough V node into the ventricles

Question 13

Long term treatment of arrhythmias

Answer 13

Permanent pacemaker

Question 14

Tachyarrhythmias fall into 2 categories:

Answer 14

1. Above Ventricle
   - Supraventricular Tachycardias (SVT)
2. Ventricle
   - Ventricular Tachycardia
   - Ventricular Fibrillation

Question 15

SVT can be classified under two categories:

What do they consist of?

Answer 15

1. Regular
   - 1 P : 1 QRS
2. Irregular
   - AF
   - MAT
   - AFL

Question 16

Atrial Fibrillation (AF)

Answer 16

A type of Irregular SVT where there are no discrete P waves

Question 17

Multifocal Atrial Tachycardia

Answer 17

MAT: a type of irregular SVT where there are 3 or more P waves

Question 18

Atrial flutter (AFL)

Answer 18

AFL: a type of irregular SVT where one would see variable conduction and flutter waves

Question 19

Types of Regular SVT

Answer 19

1. sinus tachycardia,
2. AV nodal reentrant tachycardia,
3. atrioventricular reentrant
4. tachycardia,
5. atrial flutter (can also be irreg)
6. atrial tachycardia,
7. junctional tachycardia

*management for these hinges on their diagnosis!

Question 20

How are Irregular SVT treated?

Answer 20

control their rates (assess symptoms),

Then use antiarrhythmics, or cardiovert them (hemodynamic collapse)

Question 21

How are regular SVT treated?

Answer 21

first step is both a diagnostic and treatment option, which is to use adenosine, a drug that blocks the AV node very transiently.

Question 22

Treatment of Atrial fibrillation

Answer 22

5 C’s

Cause: Reverse

Control Rate

antiCoagulation

Control Rhythm

? Cure: Ablation

Question 23

What is the most common atrial arrhythmia?

Answer 23

A fib

- also the most complicated

Question 24

Causes of A fib (AF)

Answer 24

Hypertension 14%
IHD
Mitral valve Disease
Alcohol
Cardiomyopathies
Hyperthyroidism
Lone AF      14%

Question 25

2 ways to control rhythm

Answer 25

1. pharmacological
   - Class IC agents
   - Class III agents
   - anticoags (bc of risk for thrombo)
2. electrical
   - DC shock

Question 26

Ways to control rate

Answer 26

Betablockers 
Digoxin
Verapamil
Diltiazem
 Amiodarone - can be used as a rate-controlling agent, especially in setting of decompensated heart failure.

Question 27

What happens if pts fail medications for rhythm control?

Answer 27

Use catheter ablation - target triggers of atrial fib.

• 95% cure rate for Atrial flutter and low risk

Question 28

If you are uncertain when making a diagnosis on an arrhythmia, what should you err on?

Answer 28

err on treating the arrhythmia as a ventricular arrhythmia

• If pt has coronary artery disease, 90% of the time the WCT is VT

Question 29

When should you use implantable defibrillators?

Answer 29

if pt has structural heart disease
if pt is high risk for sudden cardiac death (SCD)
- ONLY available treatment for SCD