Lecture 8 - Arrhythmias 2

Question 1

goals of anti arrhythmic therapy

Answer 1

1. Dec or inc conduction velocity
2. alter excitability of cardiac cells by changing the duration of the effective refractory period
3. Suppress abnormal automaticity

Question 2

Vaughan-williams Classification

Answer 2

Class 1- 1A, 1B, 1C
Class 2
Class 3
Class 4

Question 3

Class 1A drugs

Answer 3

Moderate Na+ blockers = fast fibers

Drugs: Quinidine, Procainamide, Disopyramide

Question 4

What do Class 1A drugs do?

Answer 4

Dec conduction velocity
Inc refractory period
Dec automaticity

Prolongs QT

Question 5

What are Class 1A drug used for?

Answer 5

useful for Supraventricular and ventricular dysrhythmias

Question 6

Class 1B drugs

Answer 6

Weak Na+ blockers = fast fibers

Drugs: Lidocaine, Mexilitine, Phenytoin

Question 7

What do Class 1B drugs do?

Answer 7

No effect on conduction velocity
Dec refractory period
Dec automaticity

** More effect on Fast HR, no real effect on slow **

Question 8

Class 1B used for?

Answer 8

Ventricular dysrhythmias only

Question 9

Class 1C drugs?

Answer 9

Strong Na+ blockers = fast fibers

Drugs: Flecainide, Propafenone

Question 10

What do Class 1C drugs do?

Answer 10

Profoundly dec conduction velocity
No sig effect on refractory period
Dec automaticity

Question 11

What are Class 1C drugs used for?

Answer 11

effective in both supraventricular and ventricular dysrhythmias

** don’t use in pts w/ CVD secondary to pro arrhythmia and mortality **

Question 12

Class 2 Drugs

Answer 12

Work at SA/AV nodal tissue

Drugs: Beta-blockers

Question 13

What do Class 2 Drugs do?

Answer 13

Block catecholamines
Dec conduction velocity
Inc refractory period (nodal tissue)
Dec automaticity

Question 14

What are Class 2 drugs used for?

Answer 14

slowing ventricular response to supraventricular tachycardias (A-Fib)

Question 15

Class 3 Drugs

Answer 15

K+ blockers = fast fibers

Drugs: Amiodarone, Dofetilide, Dronedarone, Ibutilide, Sotalol

Question 16

What do Class 3 Drugs do?

Answer 16

don’t effect conduction velocity (except amiodarone/dronedarone)

profound inc in refractory period

no effect of automaticity (except amiodarone/dronedarone/sotalol)

**prolongs QT (rare with amiodarone)

Question 17

What are Class 3 drugs used for?

Answer 17

both supraventricular and ventricular dysrhythmias

Question 18

Class 4 drugs

Answer 18

Blocks Ca Channel

Drugs: Diltiazem, Verapamil

Question 19

What do Class 4 drugs do?

Answer 19

Dec conduction velocity
Inc refractory period (nodal tissue)
Dec automaticity

Question 20

What are Class 4 drugs used for?

Answer 20

slowing ventricular response to supraventricualr tachycardias (A-Fib)

Question 21

Class I mortality info

Answer 21

Avoid in pts for short or long-term use

Ok in pt without CAD or CHF (studies show inc morality)

Question 22

Class 3 mortality info

Answer 22

class of choice for pt with CAD and CHF

Avoid Sotalol and Dronedarone in pt w/ CHF

Amiodarone may have mortality benefit

Question 23

Amiodarone MOA

Answer 23

1. Prolongs repolarization, lengthen refractoriness, slows AV conduction, inhibits automaticity, and has nonspecific B-blocking properties
2. QT prolongation is minimal

Question 24

Amiodarone Uses

Answer 24

1. Ventricular and atrial arrhythmias
2. considered most effective anti arrhythmic available
3. Can be used in pts w/ CVD and decompensated HF

Question 25

Amiodarone Dosing IV (Supraventricular arrhythmias)

Answer 25

150 mg over 10-30 min, followed by 1mg/min X 6hrs, then 0.5mg/min X 18hrs, then 400 mg PO BID-TID until 10 grams total....then maintenance therapy with 200-400 mg/day

Question 26

Amiodarone Dosing Oral (Supraventricular arrhythmias)

Answer 26

1.2-1.8 g/day in divided doses until 10g total, then 200-400 mg/day

Question 27

Amiodarone Toxicity: CVD

Answer 27

Hypotension AV block Bradycardia V-tach ** careful in elderly**

Question 28

Amiodarone Toxicity: Endocrine

Answer 28

Hypo-/Hyperthyroidism (Hypo most common)

Question 29

Amiodarone Toxicity: Dermatological

Answer 29

Photosensitivity Bluish-slate gray discoloration of skin Phlebitis (if using IV)

Question 30

Amiodarone Toxicity: Opthalmologic

Answer 30

Visual disturbances Halo vision Corneal microdeposits Optic neuritis (rare)

Question 31

Amiodarone Toxicity: Pulmonary

Answer 31

Pulmonary pneumonitis Risk factors: >400mg/day, COPD+Asthma, Elderly, Smoking

Question 32

Two types of Pulmonary pneumonitis

Answer 32

``` Hypersensitivity pneumonitis (ARDS) (within weeks) Interstitial pneumonitis ( ~ about a month) ```

Question 33

Amiodarone Toxicity: Neurologic

Answer 33

``` Abnormal gait/ataxia Dizziness Fatigue insomnia poor coordination peripheral neuropathy Tremor ```

Question 34

Amiodarone Toxicity: Hepatic

Answer 34

AST or ALT > 2x ULN, hepatitis or cirrhosis

Question 35

Amiodarone Toxicity: GI

Answer 35

N,V, anorexia Constipation, abdominal pain abnormal salivation and taste

Question 36

Amiodarone Drug Interactions

Answer 36

Inc lvls of... CSA, digoxin, flecainide, statins, warfarin, many more

Question 37

Dofetilide MOA

Answer 37

Blocks K+ channels and profoundly inc refractory period but doesn't alter conduction velocity or automaticity Strong QT-prolonging agent No negative inotropic effects and no significant effects on HR or BP

Question 38

Dofetilide Uses

Answer 38

A-fib/A-flutter (not for ventricular arrhythmias) Can be used in pts w/ CVD and decompensated HF

Question 39

Dofetilide Dosing

Answer 39

500mcg PO BID Dosing dependent on QTc + Renal function QTc must be determined prior to 1st dose 1st time starters must stay in hospital for min of 3 days

Question 40

Dofetilide CI

Answer 40

1. Weak substrate of CYP3A4 | 2. Avoid drugs that strongly inhibit CYP3A4 or prolong QT interval

Question 41

Absolute CI for Dofetilide

Answer 41

1. Long QT Syndromes 2. Baseline QTc > 440 msec 3. CrCl < 20ml/min (known how to calc)

Question 42

which drugs cant you use with Dofetilide

Answer 42

``` Cimetidine Dolutegravir HCTZ itraconazole Ketoconazole megestrol proclorperazine trimethoprim verapamil ```

Question 43

Chest X-Ray & Opthalmologic eval timeframe (amiodarone)

Answer 43

BL, Q12 months

Question 44

Pulmonary function test & ScCR/Electrolytes, Neurologic/GI/Derm eval time (amiodarone)

Answer 44

BL, PRN

Question 45

Thyroid & Liver function Test Eval time (amiodarone)

Answer 45

BL, Q6 months

Question 46

ECG eval time (amiodarone)

Answer 46

BL, q3-6 months