Anti-arrhythmics Flashcards
What’s heart rate (u)
HR describes the frequency of depolarization of the ventricles
What’s arrhythmias?
Caused by abnormalities in the formation and/or conduction of these electrical impulses
What’s the normal resting HR (normal sinus rhythm - NSR)? (U)
60-100 beats per minute
Can Arrythmias be silent? (U)
Yes
In most pts that experience sx, what do they experience?
Palpitations (feeling like there’s fluttering or racing)
Dizziness
Lightheadedness
SOB
Chest pain
Fatigue
In severe cases, what sx may one experience?
Syncope
Heart failure
Death
What’s the most common etiology of arrhythmias?
Myocardial ischemia
OR
Infarction secondary to coronary artery dx
List the non-cardiac conditions that may trigger arrhythmias.
Electrolyte imbalances especially those involving potassium, magnesium, sodium and calcium
Elevated sympathetic states such as hyperthyroidism and infection
List the electrolytes that may trigger arrhythmias when they are out of balance
Potassium
Magnesium
Sodium
Calcium
What’s QT prolongation?
Drug- induced slowing of repolarization, which can result in a particularly dangerous ventricular tachyarrhythmia called Torsade de Pointes (TdP)
What’s the resting value?
-90 mV
What happens in phase 0 of action potential?
Depolarization (determines conduction velocity)
Na channels OPEN (entering cell)
What determines conduction velocity?
Depolarization
What’s the value of phase 1 of action potential?
+ 10mV
What happens in phase 1 of action potential?
PEAK
Na channels CLOSE
What happens in phase 2 (plateau)?
PLATEAU
Ca channels OPEN (entering cell)
K channels OPEN (EXITING cell)
What happens in phase 3?
Repolarization
Ca2+ channels CLOSE
K channel stays open (continue exiting cells)
Na may enter cell (late inward Na current)
What happens in phase 4?
Automaticity
Slow increase in potential
When is refractory period of action potential?
Phase 1 to end of phase 3
How’s arrhythmias classified?
Based on their location of origin into:
Supraventricular
OR
Ventricular
What’s Supraventricular arrhythmias?
Arrhythmias originating ABOVE atrioventricular node
What’s ventricular arrhythmias?
Originating BELOW the atrioventricular node
What’s the most common Supraventricular arrhythmias? (U)
Atrial fibrillation (AFib)
What’s AFib?
Results from multiple waves of electrical impulses in the atria, resulting in an irregular and usually RAPID VENTRICULAR RESPONSE
Why does the mgt of AFib involve anticoagulation?
Due to disorganized depolarization of the atria, coordinated atrial contraction is impaired, which increases the risk of thromboembolism and stroke
What type of ventricular tachycardia is a medical emergency?
Ventricular tachycardia without a pulse
What’s a risk factor for Torsade De Pointes (TdP)? (U)
Prolongation of the QT prolongation
What’s Torsade de Pointes (TdP)? What can it result in?
TdP is a particularly lethal ventricular tachyarrhythmia which is most commonly ass. with drugs and can result in SUDDEN CARDIAC DEATH
How is QT interval measured? What’s the measured space define?
From beginning of the QRS complex to the end of the T wave
Reflect ventricular depolarization and repolarization
What pre-existing condition may cause additive QT prolongation?
Any pre-existing cardiac condition
What class of antiarrhythmics also result in additive QT prolongation? (U)
Class Ia (Disopyramide, Quinidine, Procainamide) double quarter pounder
Class III (Amiodarone, Ibutilide, Dofetilide, Dronedarone, Sotalol) AIDDS
Name main antibiotics that may cause additive QT prolongation. (U)
Quinolones (Ciprofloxacin, Levo, Moxi, Nor, Ofloxacin, Gemi, Spar)
Macrolides (Azithromycin, Erythromycin, Clarithromycin, Telithromycin)
Which Azole antifungal is most responsible for causing additive QT prolongation? (U)
Voriconazole
Which anticancer is most responsible for causing additive QT prolongation? (U)
Nilotinib
Which SSRI is most responsible for causing additive QT prolongation? (U)
Citalopram (Celexa)
What’s the max dose of citalopram to prevent additive QT prolongation?
40mg/d
When is 20mg citalopram the max dose to prevent additive QT prolongation?
60+ years Liver impairment HF S/P MI 2C19 poor metabolizer Pt on 2C19 inhibitors Taking QT prolonging drugs
Whats the max dose in for Escitalopram (Lexapro) to prevent additive QT prolongation?
In the elderly?
20mg/d
Don’t exceed 10mg/d
What’s the preferred antidepressant in cardiac pts to prevent QT prolongation?
Sertraline (Zoloft)
What antidepressant should be avoided if pt has cardiac risk?
Citalopram
Which antiemetic agent is most responsible for causing additive QT prolongation? (U)
5-HT3-receptor antagonists (Dolasetron, Ondansetron, Granisetron, Palonosetron)
Which antipsychotic is most responsible for causing additive QT prolongation? (U)
Thioridazine
Which other agent is most responsible for causing additive QT prolongation? (U)
Methadone
What’s the 2 main reasons antiarrhythmic drugs are used?
Class I and III (used to terminate arrhythmias and restore and maintain normal sinus rhythm)
Class II and IV and Digoxin (used to slow ventricular rate during a Supraventricular arrhythmias)
What class of antiarrhythmic drugs is used to terminate arrhythmias and restore and maintain normal sinus rhythm?
Class I and III
Disopyramide, Quinidine, Procainamide,
Lidocaine, Mexiletine, Phenytoin,
Flecainide, Propafenone,
Amiodarone, Ibutilide, Dofetilide, Dronedarone, Sotalol (AIDDS)
What class of antiarrhythmic agent is used to slow ventricular rate during a Supraventricular arrhythmias?
Class II
Beta-blockers e.g. Esmolol, Propranolol)
Class IV
Verapamil, Diltiazem
Digoxin
What must be done prior to starting any medication for NON-LIFE-THREATENING arrhythmia? (U)
Check pts electrolytes
AND
Run a toxicology screen
What’s the Vaughan Williams classification of antiarrhythmics?
Class I a, b, c
Class II
Class III
Class IV