Cardiology Flashcards
GDMT for HFrEF
Includes 4 medication classes: Angiotensin-converting enzyme inhibitors (ACEi) or angiotensin-receptor blockers (ARB), or angiotensin-receptor neprilysin inhibitors (ARNI), HF-specific beta-blockers, aldosterone antagonists, and sodium-glucose cotransporter 2 inhibitors (SGLT2i).
CRT-D (abbreviation) & CRT-P
Cardiac resynchronization therapy with defibrillation (D) or pacemaker (P)
Procainamide
Anti-arrythmic. Class IA Sodium Channel Blocker.
IV or PO with the onset of action in 10 to 30 minutes. Binds to fast sodium channels inhibiting recovery after repolarization. Prolongs action potential. Decreased myocardial excitability and contractility. Some negative inotropic effects w/ peripheral vasodilation.
Used for ventricular arrhythmias, supraventricular arrhythmias, a fib/flutter, AV nodal re-entrant tachycardia, and WPW.
Metabolized hepatically via acetylation. Half life is 2-5 hours. Oral dosing for supraventricular arrhythmia is at 50 mg/kg/24 hours divided into doses every 6 hours. IV dosing is a loading dose 10 to 17 mg/kg over 20 to 50 mg/min, then 1-4mg/min. Generally used w/HF patient’s as alternative or adjuvant to amiodarone.
Quinidine
Class IA Sodium channel blocker- prolongs repolarization leading to increased action potential duration and effective refractory period.
Quinidine syncope and torsades de pointes are frequently associated with significant QT prolongation precipitated or aggravated by hypokalemia, hypomagnesemia, and bradycardia, and concurrent therapy with digitalis. Other antiarrhythmic drugs that prolong the QT interval (such as procainamide, disopyramide, amiodarone, and sotalol) should be avoided.
Ventricular arrhythmias (off-label dose): Oral: Note: Dosing regimens for suppression of ventricular arrhythmias have not been adequately studied.
Reduce total daily dose if at any time during therapy, the QRS complex widens to 130% of its pretreatment duration, the QTc interval widens to 130% of its pretreatment duration and is >500 msecs, P waves disappear, or the patient develops significant tachycardia, symptomatic bradycardia, or hypotension.
Quinidine sulfate: Initial: 200 mg every 6 hours; may increase dose cautiously up to 600 mg every 6 to 12 hours.
Sodium Channel Blockers
Class I Drug (VW Classification) These drugs prevent sodium from getting through cell membranes. This can slow electrical impulses in the heart muscle. Since pacemaker cells use calcium ions to depolarize, sodium channel blockers have little effect on the SA node and AV node (pacemaker cells).
For this reason, sodium channel blockers are useful in re-entry tachyarrhythmias where blocking the AV node could be detrimental.
It is important to note that there are 3 main classes to sodium channel blockers: Class IA, Class IB, and Class IC. Some sodium channels increase action potential duration and effective refractory period by having a prolonged repolarization phase (class IA), some decrease action potential duration and effective refractory period by having a shortened repolarization phase (class IB), and some have no effect on either action potential duration, effective refractory period, or repolarization phase (class IC).
Antiarrhythmics, based on the Vaughan-Williams (VW) classification system
Class I: Sodium Channel Blockers
Class II: Beta Blockers
Class III: Potassium Channel Blockers
Class IV: Calcium Channel Blockers
Flecainide
Class IC anti-arrhythmic/sodium channel blocker. Mainly used as a preventative drug.
Ventricular arrhythmias (prevention): Oral: Initial: 50 to 100 mg every 12 hours; increase by 50 mg twice daily at 4-day intervals; maximum: 400 mg/day. Some patients inadequately controlled with or intolerant to dosing every 12 hours may require dosing every 8 hours.
Paroxysmal atrial fibrillation/flutter and paroxysmal supraventricular tachycardias (prevention): Oral: Initial: 50 mg every 12 hours; increase by 50 mg twice daily at 4-day intervals; maximum dose: 300 mg/day. The AHA/ACC/HRS atrial fibrillation guidelines recommend a maximum dose of 400 mg/day.
Flecainide has a narrow therapeutic index, and the half-life is prolonged in patients with kidney impairment.
Mexiletine
Class IB anti-arrhythmic/sodium channel blocker
Initial: 150 to 200 mg every 8 to 12 hours (may load with 400 mg if necessary); adjust dose as needed in 50 or 100 mg increments no more frequently than every 2 to 3 days up to 300 mg every 8 to 12 hours; usual dose: 150 to 300 mg every 8 to 12 hours; maximum dose: 1.2 g/day.
Conversion:
Switching from other oral antiarrhythmics (eg, disopyramide, quinidine sulfate): Initiate 200 mg dose of mexiletine 6 to 12 hours after the last dose of the former agent.
Switching from IV lidocaine: Initiate 200 mg dose of mexiletine when lidocaine infusion is stopped.
Switching from oral procainamide: Initiate a 200 mg dose of mexiletine 3 to 6 hours after the last dose of procainamide.
Lidocaine (cardiac)
Class IB anti-arrhythmic/sodium channel blocker
Sudden cardiac arrest due to ventricular fibrillation or pulseless ventricular tachycardia, unresponsive to cardiopulmonary resuscitation, defibrillation, and epinephrine (off-label use):
IV, intraosseous: Initial: 1 to 1.5 mg/kg bolus. If refractory ventricular fibrillation or pulseless ventricular tachycardia, repeat 0.5 to 0.75 mg/kg bolus every 5 to 10 minutes (maximum cumulative dose: 3 mg/kg). Follow with continuous infusion (1 to 4 mg/minute) after return of perfusion
Reappearance of arrhythmia during continuous infusion: Give an additional 0.5 mg/kg bolus then increase infusion.
Endotracheal (loading dose only) (off-label route): 2 to 3.75 mg/kg (2 to 2.5 times the recommended IV dose); dilute in 5 to 10 mL NS or sterile water. Note: Absorption is greater with sterile water and results in less impairment of PaO2
Ventricular tachycardia, hemodynamically stable:
IV: 1 to 1.5 mg/kg; repeat with 0.5 to 0.75 mg/kg every 5 to 10 minutes as necessary (maximum cumulative dose: 3 mg/kg). Follow with continuous infusion of 1 to 4 mg/minute or 20 to 50 mcg/kg/minute.
Note: For prolonged infusion (after 24 hours), reduce the rate of infusion by approximately one-half to compensate for the reduced elimination rate. Administer under constant ECG monitoring.
Phenytoin
Class IB anti-arrhythmic/sodium channel blocker
Used for seizures….
Action potentials of pacemaker cells
We used the following catchphrase to remember the action potentials of pacemaker cells (found primarily in the cardiac conduction system - SA node, AV node, etc.).
“Climb and Plummet”
This helped us remember the following action potential phases of pacemaker cells:
Phase 0: Climb = Calcium In
Phase 3: Plummet = Potassium Out
Phase 4: “Resting” Phase
“Double Quarter Pounder, Lettuce Tomato Pickle Mayo, Fries Please”
Class 1A = “Double Quarter Pounder”
This will help you remember Disopyramide, Quinidine, and Procainamide are class IA sodium channel blockers.
Procainamide commonly shows up on medical tests and licensure exams, especially for the treatment of WPW.
Class IB = “Lettuce Tomato Pickle Mayo”
This will help you remember Lidocaine, Tocainide, Phenytoin, and Mexiletine are class IB sodium channel blockers.
Lidocaine and phenytoin are usually the class IB medications tested as they are more common.
Class IC = “Fries Please”
This will help you remember Flecainide and Propafenone are class IC sodium channel blockers.
Flecainide is the more common one and is what is usually tested.
Class 1A Anti-Arrhythmics
Class 1A = “Double Quarter Pounder”
This will help you remember Disopyramide, Quinidine, and Procainamide are class IA sodium channel blockers.
Procainamide commonly shows up on medical tests and licensure exams, especially for the treatment of WPW.
Class 1B Anti-Arrhythmics
This will help you remember Lidocaine, Tocainide, Phenytoin, and Mexiletine are class IB sodium channel blockers.
Lidocaine and phenytoin are usually the class IB medications tested as they are more common.
Class 1C Anti-Arrhythmics
Flecainide and Propafenone are class IC sodium channel blockers.
Flecainide is the more common one and is what is usually tested.
