Chapter 27: Drug Therapy for Dysrhythmias Exam 2

What is the normal electrical pathway of the heart?

SA node → AV node → Bundle of His → Bundle Branches → Purkinje Fibers

What is the SA node?

The pacemaker of the heart that normally starts the electrical impulse.

What is the role of the AV node?

Acts like a "bouncer" that checks impulses before allowing them through.

What is automaticity?

The ability to generate an electrical impulse.

What is excitability?

The ease in which cardiac cells respond to electrical events.

What is conductivity?

The ability of cardiac tissue to transmit electrical impulses.

What is inotropy?

negative: decreases contractility
positive: increases contractility

What is chronotropy?

negative; decreases HR
positive: increases HR

Dromotropy effects electrical conduction through AV node

negative: decreases electrical conduction
positive: increases electrical conduction

What are common atrial dysrhythmias?

Atrial flutter and atrial fibrillation (AFib).

What are common ventricular dysrhythmias?

Ventricular tachycardia (VTach) and ventricular fibrillation (VFib).

Which dysrhythmias are considered lethal?

Ventricular tachycardia and ventricular fibrillation.

What is sinus bradycardia?

Heart rate that is too slow.

What is sinus tachycardia?

Heart rate that is too fast.

What is cardioversion? (Nonpharmacologic Therapy)

Shocking a patient back into a normal rhythm.

What is radiofrequency catheter ablation? (Nonpharmacologic Therapy)

Burning the abnormal electrical pathway to force the heart to use the normal pathway.

Why are pacemakers used? (Nonpharmacologic Therapy)

To increase a slow heart rate.

What is an AICD? (Nonpharmacologic Therapy)

Automated Implantable Cardioverter Defibrillator that automatically shocks lethal dysrhythmias.

What are the main actions of antidysrhythmic drugs?

• Reduce automaticity

• Slow impulse conduction

• Prolong refractory period

What is the refractory period?

The resting period of the heart.

Why are antidysrhythmic drugs used?

• Convert AFib/AFlutter to normal sinus rhythm

• Maintain normal sinus rhythm

• Suppress dangerous ventricular rhythms

• Treat potentially fatal dysrhythmias

How do Class I antidysrhythmics work?

Block cardiac sodium channels and slow conduction.

Examples of Class IA sodium channel blockers?

• Quinidine

• Procainamide

• Lidocaine

Black box warning for Quinidine and Procainamide?

Should only be used for fatal dysrhythmias because they can cause severe dysrhythmias themselves.

What dysrhythmias is Lidocaine used for?

Ventricular dysrhythmias only. NEVER atrial

How do beta blockers treat dysrhythmias?

Decrease conduction through the SA and AV nodes, decrease automaticity, and slow heart rate.

How do beta blockers affect the heart?

• Decrease heart rate

• Decrease contractility

• Decrease conduction

Examples of beta blockers used for dysrhythmias?

• Metoprolol

• Propranolol

Black box warning for beta blockers?

Do not stop abruptly in patients with CAD because it may cause chest pain or MI.

Major adverse effects of beta blockers?

• Bradycardia

• Hypotension

• Bronchoconstriction (nonselective) → Propranolol

• Masked hypoglycemia

Why should beta blockers be avoided in asthma?

Nonselective beta blockers can cause bronchoconstriction.

How do Class III antidysrhythmics work?

Block potassium channels, slow heart rate, prolong conduction, and cause some vasodilation.

What is the best drug class for atrial fibrillation?

Class III Potassium Channel Blockers.

What ventricular dysrhythmias are treated with Class III ( Potassium Channel Blockers) drugs?

VTach and VFib.

What is Amiodarone?

A Class III potassium channel blocker

What is Amiodarone used for?

• Atrial fibrillation

• Ventricular tachycardia

• Ventricular fibrillation

How can Amiodarone be given?

IV or oral.

IV Amiodarone is used for what?

Acute dysrhythmias.

Oral Amiodarone is used for what?

Maintenance therapy.

Black box warning for Amiodarone?

Pulmonary toxicity.

What pulmonary symptoms may indicate Amiodarone toxicity?

• Dyspnea

• Cough

• Crackles

• Low oxygen saturation

• Increased respiratory rate

What serious liver effect can Amiodarone cause?

Hepatotoxicity

Signs of hepatotoxicity?

• Jaundice

• Abdominal pain

Why can Amiodarone cause thyroid dysfunction?

It is an iodine-rich drug.

Other major adverse effects of Amiodarone?

• Bradycardia

• Blurry vision

• Photosensitivity

• Blue skin discoloration

• Drug interactions

Why do Amiodarone and anticoagulants commonly interact?

Many patients with AFib take anticoagulants.

What can happen when IV Amiodarone is given as a loading dose?

Hypotension

When should Amiodarone be avoided or used cautiously?

• Heart block

• Severe bradycardia

• Hypokalemia

• Iodine allergy

• Thyroid disease

• Liver disease

• Pulmonary disease

What class is Dofetilide?

Class III Potassium Channel Blocker.

Black box warning for Dofetilide?

QT prolongation

What is QT prolongation?

Ventricles take too long to relax, increasing risk of lethal dysrhythmias.

Why must patients be hospitalized when starting Dofetilide?

Need kidney monitoring and repeated 12-lead ECGs.

What must be monitored before and after Dofetilide doses?

QT interval on ECG.

Contraindications for Dofetilide?

• Heart block

• Renal dysfunction

• Prolonged QT interval

Which calcium channel blockers are used for dysrhythmias?

• Diltiazem

• Verapamil

What type of calcium channel blockers are Diltiazem and Verapamil

Non-dihydropyridines.

How do Class IV calcium channel blockers work?

Reduce automaticity, slow AV node conduction, and slow heart rate.

How do calcium channel blockers treat dysrhythmias?

They slow the heart rate.

What dysrhythmias are calcium channel blockers best for?

• Atrial fibrillation

• Supraventricular tachycardia (SVT)

What heart rate is considered SVT?

Greater than 150 bpm.

Major adverse effects of Diltiazem and Verapamil?

• Bradycardia

• Hypotension

• Peripheral edema

Contraindications for Diltiazem and Verapamil?

• Heart block

• Bradycardia

• Hypotension

What should patients avoid while taking Diltiazem or Verapamil?

Grapefruit or grapefruit juice.

What medications require extra monitoring with Diltiazem or Verapamil?

• Beta blockers

• Digoxin