850-Arrhythmias (section 2)

Question 1

Supraventricular Tachyarrhythmia (SVT):

Answer 1

1. Sinus arrhythmia
2. Atrial arrhythmia
3. Nodal arrhythmia (junctional)

Question 2

Arrhythmia Types - Tachycardia (FAST)

Answer 2

Fast Arrhythmias:

1. Sinus Tachycardia (SA node)
2. Atrial Tachycardia
3. Atrial fibrillation/flutter
4. AV- nodal re-entry tachycardia
5. Wolff- Parkinson White Syndrome (WPW)
6. Ventricular Tachycardia
7. Ventricular Fibrillation

Question 3

Arrhythmia Types - Bradycardia (Slow)

Answer 3

Slow Arrhythmias:

1. Sinus Bradycardia (SA node)
2. AV-nodal block
   - 1st, 2nd, 3rd degree block
3. Asystole (absence of ventricular contractions)

Question 4

Heart Rates in beats per minute:

Fibrillation (Atrial or Ventricular)

Answer 4

500

Question 5

Heart Rates in beats per minute:

Atrial flutter

Answer 5

350

Question 6

Heart Rates in beats per minute:

Ventricular or Supraventricular Arrhythmia (or known as SVT or AV nodal re-entry tachyarrhythmia, WPW)

Answer 6

150 to 250

Question 7

Heart Rates in beats per minute:

Normal Range

Answer 7

60 to 100

Question 8

Heart Rates in beats per minute:

Mild-Moderate Bradycardia

Answer 8

40

Question 9

Heart Rates in beats per minute:

Severe bradycardia

Answer 9

20

Question 10

Etiology of Arrhythmias (Setting the Environment)– 2 Main Classifications

Answer 10

1. Metabolic abnormalities:
   - Ectopic conduction/Early afterdepolarizations
   - Ischemic tissue
   - Genetic abnormalities (QT-prolongation)
   - Electrolyte Abnormalities
   - Drug Toxicity
2. Structural abnormalities:
   - Scarring/fibrotic areas of no conduction
   - Hypertrophy and cardiomyopathy
   - Accessory pathways/block/congenital malformations

Question 11

Arrhythmia Formation – 2 Main Mechanisms:

Answer 11

Two Major Mechanisms:

1. Disorder of impulse generations
   - Abnormal automaticity
   - Triggered activity, early or delayed afterdepolarizations (EAD or DAD)
2. Abnormal impulse conduction
   - Block
   - Reentry

Question 12

Disorder of Impulse Generation – Abnormal Automaticity

Answer 12

> > Slope of Phase 4«

1. Increase slope, increase automaticity (heart rate)
2. Sympathetic activity increases slope of phase 4 and thus HR
3. Cholinergic activity decreases slope of phase 4 and thus HR
4. Some antiarrhythmic drugs can change slope of phase 4 and change heart rate

Question 13

Disorder of Impulse Generation - AfterDepolarizations

Answer 13

• EAD: altered openings of CA++ or Na++ channels. Also K+ channels
• DAD: elevated cystolic Ca++ concentrations

Question 14

For Those That Are Interested More Specifics:

Afterdepolarizations:

Answer 14

Afterdepolarizations:

1. “Early” - Occur during late phase (2) or recovery (3) phase
2. “Delayed” - Occur during resting potential (Phase 4)
3. Relate to:
   - Increased L-type Calcium channel activation (ICa)
   - Increased sodium channel reactivation or
   - Sudden decreased rectifying K+ current (IKr)
4. Can be brought on by K+ channel blockers (Type III antiarrhythmics) or
5. Long QT Syndrome (genetic) or
6. Elevated cytosolic Ca++ levels (digoxin)

Question 15

Abnormal Impulse Conduction - Block

Answer 15

• Area of tissue that does not conduct electrical impulse (action potential)
• Most important areas – SA node, AV node, or His-purkinje system (i.e., bundle branch)

Question 16

Abnormal Impulse Conduction – Reentry

Answer 16

Abnormalities in impulse conduction:

• Impulses from higher pacemaker centers are normally conducted down pathways that bifurcate to activate the entire ventricular surface.
• A phenomenon called reentry can occur if a unidirectional block caused by myocardial injury or a prolonged refractory period results in abnormal conduction pathway.
• Reentry is the most common cause of arrhythmias, and it can occur at my level of cardiac conduction system

Question 17

AV-Node Reentry Arrhythmia

Answer 17

• AV-node has embedded a slow and fast pathway

- Often, a premature beat can also set up a AV-nodal reentry arrhythmia. Common arrhythmia