Chapter 32: Arrhythmias

Question 1

Symptoms of Arrhythmias

Answer 1

• dizziness
• SOB
• fatigue
• lightheadedness
• chest pain

Question 2

Normal HR

Answer 2

60-100bpm

Question 3

Cardiac Conduction Pathway

Answer 3

1. Electrical impulse begins in the SA node
2. Impulse travels from SA node to right and left atria which causes a contraction
3. When the signal reaches the AV node the electrical conduction slows down
4. Impulse continues to the bundle of His and into the ventricles
5. Bundle of His divides into right and left bundle branch of ventricles
6. Signal continues to spread through ventricles via Purkinje fibers which causes ventricles to contract

Question 4

Electrical Signaling: Cardiac Action Potential

Answer 4

Phase 0: heartbeat is initiated when rapid ventricular depolarization occurs in response to an influx of Na, causes ventricular contraction
Phase 1: early rapid repolarization (Na channel closes
Phase 2: a plateau in response to influx of Ca and efflux of K
Phase 3: rapid ventricular repolarization in response to efflux of K, causes relaxation of ventricles
Phase 4: resting membrane potential is established, atrial depolarization occurs (p-wave)

Question 5

Supraventricular Arrhythmias

Answer 5

Originate above the AV node

Question 6

Ventricular Arrhythmias

Answer 6

Originate below the AV node
Premature ventricular contractions (PVCs) “skipped heartbeat” originate in ventricular tissue and are sometimes related to stress, caffeine, nicotine, or exercise
Series of PVCs in a row resulting in HR >100bpm is ventricular tachycardia (VT). Untreated VT can degenerate into ventricular fibrillation which is a medical emergency

Question 7

Afib

Answer 7

Most common type of supraventricular arrhythmia. It occurs when multiple waves of electrical impulses in the atria result in an irregular (and usually rapid) ventricular response .
Blood clot formation risk increases.

Question 8

Drugs that can cause QT prolongation

Answer 8

• Antiarrhythmics (class I and III)
• Abx (macrolides and quinolones)
• Azole antifungals (all except isovuconazole)
• Antidepressants (tricyclics, SSRIs, SNRIs)
• Antiemetics (5ht3 antagonists, droperidol, phenothiazines)
• Antipsychotics (most)
• Other (donepezil, fingolimod, methadone, tacrolimus)

Question 9

Vaugh Williams Classification

Double Quarter Pounder, Lettuce, Mayo, Fries Please! Because Dieting During Stress Is Always Very Difficult

Answer 9

Class 1:
Ia: Disopyramide, Quinidine, procainamide
Ib: Lidocaine, Mexiletine
Ic: Flecainide, Propafenone

Class 2: Beta-blockers

Class 3: Dronedarone, Dofetilide, Sotalol, Ibutilide, Amiodarone

Class 4: Verapamil, Diltiazem

Question 10

Class 1 MOA

Answer 10

Na channel blockers

Proarrhythmics, use caution in underlying cardiac disease

Question 11

Class 2 MOA

Answer 11

Beta-blockers

Use to slow ventricular rate in AFib

Question 12

Class 3 MOA

Answer 12

K channel blockers
Sotalol blocks k channels and is a BB
Amiodarone and defetilide are preferable in pts with AFib and HF

Question 13

Class 4 MOA

Answer 13

Non-DHP CCB

Question 14

Digoxin MOA

Answer 14

NA-K-ATPase blocker

Suppress AV node conduction, decrease HR, and enhancing vagal tone and increase force of contraction (positive inotrope)

Question 15

Adenosine MOA

Answer 15

Activates adenosine receptors to decrease AV node conduction
Used for paroxysmal supraventricular tachyarrhythmia (PSVTs)

Question 16

Amiodarone

Answer 16

Nexterone, Pacerone
Boxed Warnings: pulmonary toxicity, hepatotoxicity
CI: iodine hypersensitivity
Warnings: hyper/hypothyroidism, optic neuropathy, photosensitivity (slate-blue skin), neuropathy

Question 17

Amiodarone Drug Interactions

Answer 17

When starting decrease warfarin by 30 to 50%, digoxin by 50%, DNE 20mg/day of simvastatin or 40mg/day lovastatin (use alt statin)
Do not use with Sofosbuvir
Additive effects with drugs that decrease HR (non-dhp ccb, digoxin, bb, clonidine and demedetomidine)

Question 18

Digoxin

Answer 18

Therapeutic Range 0.8-2ng/ml for Afib
CrCl <50 decrease dose or frequency
Decrease dose by 20-25% for oral to IV
Antidote: digifab

Question 19

Disopyramide

Answer 19

Ia drug
Proarrhythmic
Anticholinergic effects

Question 20

Quinidine

Answer 20

Ia drug
Warnings: proarrhythmic, hemolysis risk (avoid is G6PD deficiency), positive coombs test
SE: DILE, diarrhea, stomach cramping, Cinchonism (overdose): symptoms include tinnitus, hearing loss, blurred vision, headache delirium

Question 21

Procainamide

Answer 21

Ia
Injection
Decrease dose when CrCl <50
Therapeutic Level 4-10mcg/ml
Boxed warning: agranulocytosis, long-term use leads to positive antinuclear antibody, DILE

Question 22

Lidocaine

Answer 22

Ib
Used for refractory VT/cardiac arrest
Injection

Question 23

Flecainide

Answer 23

Ic
Proarrhythmic
CI: HF, MI

Question 24

Propafenone

Answer 24

Ic
Proarrhythmic
CI: HF, MI
SE: taste disturbance (metallic)

Question 25

Dronedarone

Answer 25

III
Boxed warnings: increased risk of death, stroke, and HF in patients with decompensated HF or permanent AFib
CI: CYP3A4 inhibitors and QT prolonging drugs

Question 26

Sotalol

Answer 26

III
Adjust dosing interval based on CrCl to decrease risk of proarrhythmia
QT prolongation is directly related to sotalol concentration

Question 27

Ibutilide

Answer 27

III
Injection
Correct hypokalemia and hypomagnesemia prior to use and throughout tx

Question 28

Dofetilide

Answer 28

III
Boxed Warning: must be initiated in a setting with continuous ECG monitoring, and ability to assess CrCl for a min of 3 days, proarrhythmic.

Question 29

Adenosine

Answer 29

Injection
T1/2 less than 10 sec
Used in paroxysmal supraventricular tachycardia (PSVTs)