Antiarrhythmic Drugs Flashcards
What are the fast action potential cells in cardiac muscle?
Ventricular contractile cardiomyocytes
Atrial cardiomyocytes
Purkinje Fibers
What are the slow action potential cells in cardiac muscle?
SA node cells, AV node cells
What happens on an EKG when you block the K+ Channels?
QT widening
What happens on an EKG when you block the Na+ channel?
QRS widening and drop contractility
This drug has ganglion blocking properties and may reduce PVR causing hypotension, also has muscarinic activity
Procainamide
Define cinchonism
Tinnitus, hearing loss, confusion, delirum, psychosis involved in Quinidine
In quinidine what organ may be affected other than the heart?
Liver - hepatitis with fever
Someone was given a drug that caused them to have tachycardia, urinary retention, blurred vision, constipation, glaucoma when it was supposed to treat their ventricular arrhythmias?
Disopyramide
Class 1B drugs bind to…
The inactivated sodium channel
Lidocaine is administered…
IV because really fast first pass metabolism
What is the least toxic of all Class I drugs?
Lidocaine
What are the neurological side effects of lidocaine?
Paresthesia, tremor, slurred speech, convulsions
This drug is related to lidocaine. How is it administered and what is it used for?
Mexilitine - orally active, used for Vtach and relieving diabetic neuropathy or nerve injury due to chronic pain
Does Class C affect K+ channels?
Yes blocks certain ones
This class IC drug is used for refractory arrhythmias that are life threatening as well as supraventricular arrythmias
Fleicainide
This class of drugs binds to open, activated Na+ Channels
Class 1C
This Class 1C drug has weak B blocking activity and is used in supraventricular arrythmias
Propafenone, but can make the arrythmia worse too lol
What are the effects of beta blockers on the AV and SA node?
AV node = drops conductance to increase PR interval
SA node = drops HR to increase RR interval
What are the effects on the calcium curve for the beta blockers?
- Increased slope due to effects on If and T-type Ca2+ channels
- Reduced threshold due to effect on L-type Ca2+ channels
This decreases the responsiveness of the Ca2+ channels to depolarization so AP is less -
What are the 4 clinical uses of propranolol?
- Stress and thyroid storm
- Afib and flutter
- Paroxysmal Supraventricular Arrhythmias
- MI arrhythmias to drop mortality
PAMS
Esmolol is administered how?
IV admin with rapid onset and termination of its action
What is esmolol used for? (5)
- Supraventricular arrhythmias
- Arrythmias associated with thyrotoxicosis
- MI or acute MI with arrythmias
- Adjunct drug in general anesthesia to control arrhythmias in periop period
SAMA
What channels do Class III drugs block?
K+ channel and inactivated sodium channels
Does Amiodarone block CCBs?
Yes
This Class III drug treats life threatening ventricular arrhtyhmias
Sotalol
This class III drug treats recurrent Vtach and Afib
Amiodarone
This Class III drug is used to restore sinus rhythm in patients with atrial fibrillation
This Class III drug is used to maintain the sinus rhythm after cardioversion in patients with atrial fibrillation
Both Dofetilide and Ibutilide
Just Dofetilide
This drug specifically blocks the rapid component of the delayed rectifier potassium current
Dofetilide and ibutilide
Explain what Class IV drugs block and what they’re active in?
- Block L-type channels
- Active in cells that exhibit pacemaker potential to decrease the slope of phase 0 and increase L-type Ca2+ threshold potential
What is the effect of Class IV drugs on the SA and AV node?
Slow SA node depolarization to drop HR
Prolong conduction time in AV node
These drugs can be used for paroxysmal supraventricular tachy and ventricular rate control in afib
Verapamil and Diltiazem
This drug can cause constipation
Verapamil
How does procainamide work on the nodes?
SA and AV node depression
How does amiodarone work on the nodes?
Causes bradycardia and slows AV conduction
What channels does adenosine act on?
Enhances K+ current and inhibit Ca2+ and funny current which causes hyperpolarization and suppresses action potentials in pacemaker cells
What is the effect of Adenosine on the nodes?
Inhibits AV conduction and increases AV nodal refractory period
What are the 4 drugs that can treat paroxysmal supraventricular tachycardia?
Adenosine, Verapamil, Diltiazem, Propranolol
DAVP
What are the 5 adverse effects of adenosine?
- SOB
- Bronchoconstriction (A1 and A2B adenosine receptors)
- Chest burning
- AV block
- Hypotension
What is CAST?
Terminated prematurely because flecainide and other class 1C drugs increased mortality by 2.5x
What is pro-arrhythmia?
Drug induced significant arrhythmia or worsening of existing arrhythmia
What should you do before starting antiarrhythmic therapy?
- Eliminate the cause
- Make a firm dx
- Consider underlying cardiac conditions and co-morbidities
- Consider nonpharm treatment of arrhythmias
What are the nonpharm appropaches to treating arrhythmias?
Catheter ablation
Implantable cardioverter-defibrillator
Artificial cardiac pacemaker
Direct current cardioversion
What are the antiarrhythmic drugs that promote torsades de pointes?
Class 1A and Class 3 Drugs leads to excessive slowing of repolarization
What are the antiarrhythmic drugs that cause persistent Vtach?
Class 1A and 1C drugs
An 80 YO patient has fatigue, weakness, decreased exercise tolerance, hypotension, pulmonary congestion, heart failure. What is the most common suspicion?
Afib
How do we achieve rhythm control in afib?
DCC or Chemical cardioversion using:
- Class 1C agents that block fast Na+ channels to drop retrograde conduction through damaged tissue to terminate reentry (only use these with Class 3 if LVEF >40%)
- Class 3 agents that block K+ channels to keep cells in refractory period to prevent reentry (always use these even if LVEF < 40%)
What is a reentry rhythm?
An obstruction must be there that leads to a circuit that exceeds refractory epriod
- One impulse reenters and excites areas of heart more than once
Which is more effective - rhythm or rate control?
Rate because rhythm has more adverse effects associated with maintenance phase
How do you treat with rate control in afib?
Assess LV function
- If No HF and LVEF > 40% then CCB or B blocker to amiodarone
- If HF and LVEF < 40% then B blocker to amiodarone
This helps with multiple waves of excitation hitting AV node it responds to fewer
What is the CHAD score used for?
Out of 9 - to determine if patient needs to be on anticoagulant to prevent stroke in AFIB pts
PSVT is characterized by… and the most common type?
Abrupt onset and termination
Most common: AVNRT
What are the common symptoms in PSVT patients?
Palpitations, dizziness, lightheaded, dyspnea, chest pain
What is the mechanism of PSVT?
Dual pathway with AV node with heterogenous electrophysiological properties allowing for re-entry circuit
Anterograde - slow
Retrograde - fast
What does PSVT look like on EKG?
Narrow QRS, inverted P wave or not seen
What is the protocol for PSVT?
- Try vagal maneuver
- Give adenosine
- If LVEF > 40% then diltiazem or verapamil, then B blocker MAP
- If LVEF < 40% of hx of heart failure then give digoxin then amiodarone then diltiazem
Long QT syndrome aka
Torsades de Pointes
What are the 2 ways you can get Torsade de Pointes?
- Congenital = due to K+ or Na+ mutations
- Acquired long QT = factors that prolong action potential duration like slow HR or electrolyte imbalances OR antiarrhythmic drugs acting on Class 1A and 3, antipsychotics, antibiotics
Chloroquine and Hydroxychloroquine and Azithromycin for COVID leads to
TDP
How do we treat TDP?
- Stop the drug
- Hemodynamically unstable: DCC
- Hemodynamically stable: correct metabolites, Magnesium sulfate by IV whether or not they need it, temporary pacemaker/isoproterenol IV
