Cardio II Flashcards
What is the consequence of arrhythmias in terms of mechanical performance?
Ventricular stroke volume may be directly affected, leading to a decrease in cardiac output
What is the consequence of arrhythmias in terms of proarrhythmic/arrhythmogenic?
If not corrected, may lead to more severe forms of arrhythmias
What is the consequence of arrhythmias in terms of thrombogenesis?
Chronic arrhythmias may lead to the generation of thrombin in heart chambers
What are the four ways of decreasing spontaneous activity?
- Decreased phase 4 slope
- Increased threshold
- Increased maximum diastolic potential
- Increased AP duration
What are the two ways of increasing refractoriness?
Na channel blocker or AP prolonging
What is the MOA of Na channel blockers to increase refractoriness?
Shifts the voltage dependence of recovery
What is the MOA of AP prolonging drugs?
Blocks K channels, to slow the rate of K efflux
What is the general MOA of class I agents?
Block fast Na channels in the conductive tissues of the heart
What is the effect of class I drugs on the maximum depolarization rate?
Decreases
What is the effect of class I drugs on the automaticity and conduction?
Reduce automaticity
Delay conduction
What is the effect of class I drugs on ERP?
prolonged, leading to increased ERP/APD
What are the two major diseases that class I drugs are used in?
MI induce arrhythmias
Ventricular dysrhythmias
What type of drug is quinidine?
Class Ia
What type of drug is procainamide?
Class Ia
What type of drug is disopyramide?
Class Ia
What are the three class Ia drugs?
Quinidine
Procainamide
Disopyramide
What type of drug is lidocaine?
Class Ib
What type of drug is mexiletine?
Class Ib
What type of drug is propafenone?
Class Ic
What type of drug is flecainide?
Class Ic
What is the MOA of class Ia drugs? How does this affect the depolarization curve? (3)
Blocks both Na and K channels, and blocks Ca channels at high doses
Na block = prolonged phase 0
K blocked = delayed phase 3 repolarization
Ca blocked = depressed phase 2 and nodal phase 0
What is the primary MOA of quinidine?
Blocks rapid Na channel, lowering Vmax of phase 0
Causes slowed conduction
What are the three dose- dependent effects of quinidine?
- Blocks K channels (Increased APD)
- Blocks alpha receptors (lower BP)
- Blocks M receptors (higher HR)
What are the applications of quinidine?
only used in refractory cases of AF/ atrial flutter
What are the adverse effects of Quinidine? (4)
n/v/d
Cinchonism
Hypotension
Proarrhythmic
What is cinchonism, and what drug may cause it?
Tinnitus, hearing loss, blurred vision
Quinidine
How can Quinidine decrease Bp?
blocking alpha receptors
How can Quinidine cause torsades de pointes?
Block K channels can lead to an increased QT via prolonged plateau
What is the MOA of Procainamide? (2)
Blocks rapid inward Na channel to slow conduction
Blocks K channels to prolong APD and refractoriness
What are the clinical application of Procainamide? (4)
Suppress life threatening ventricular arrhythmias
Reentrant SVT
A-fib
A-flutter d/t WPW
What is the effect of Procainamide on M and alpha receptors? Consequence of this?
None, thus no hypotension or tachycardia
What is wolf-parkinson white syndrome (WPW)?
two pathways of ventricular conduction (slow and fast)
What are the adverse cardiac effects of Procainamide?
Arrhythmia aggrevation
Torsades de pointes
What are the adverse extracardiac effects of Procainamide?
SLE like syndrome
N/v
What are the drugs that should never be given to a pt with a h/o torsades de pointes?
Procainamide
Quinidine
What is the MOA of Lidocaine?
Blocks open and inactivated Na channels, causing a shortened repolarization, reduced Vmax, and lowered phase 4
What is the effect of Lidocaine on the cardiac AP?
Shortened
What are the two effects of lidocaine in abnormal conduction systems?
Slows ventricular rate
potentiates infranodal block
What is the clinical application of lidocaine?
treat ventricular arrhythmias (second choice after amiodarone)
Is lidocaine effective for prophylaxis of arrhythmias after an MI? How about in atrial tissue
No and no
Why must lidocaine be given IV, with multiple loading doses?
Has an extensive first pass effect
What are the adverse reactions of lidocaine?
tinnitus/Szs in rapid bolus
What is the MOA of class Ic drugs?
Strong binding to Na channels, causing strong effects on phase 0 depolarization
What is the effects of class Ic drugs on Qt interval? QRS complex? PR?
QT unchanged
Longer QRS
Longer PR
What type of drug is propafenone? MOA?
Class Ic
Strongly inhibits Na channels
What is the adverse effect of propafenone?
beta adrenergic inhibition =
Propafenone looks similar structurally to what drug? What is the consequence of this?
Propranolol
Lowers HR and ventricular output
Why should you avoid giving pts with heart failure propafenone?
beta blocking effects will decrease CO
What type of drug is Flecainide? MOA?
Class Ic
Blocks Na and prolonger 0, widens QRS, and markedly slows intraventricular conduction
What are the clinical application for Flecainide?
Refractory life-threatening ectopic ventricular arrhythmias
Why isn’t Flecainide used as a first line treatment against ventricular arrhythmias?
Propensity for fatal proarrhythmic effects
What type of drugs are class II drugs? MOA?
beta blockers
Slow SA node automaticity
Lower AV node conduction
Decrease ventricular contractility
When are class 2 drugs used?
Supraventricular arrhythmias due to excessive sympathetic activity
What is the only type of antiarrhythmic drugs found to be clearly effective in preventing sudden cardiac death in pts with prior MI?
Class ii (beta blockers)
What is the MOA of class III drugs?
Work on everything, except adenosine (Ca, Na, K, alpha, beta, ACh)
What is the main effect of class III drugs?
Prolong phase 3 repolarization (prolonged QT)
What is the clinical use of class III drugs?
Arrhythmias
What are the 5 class 3 drugs?
Dronedarone Amiodarone Sotalol Ibutilide Dofetilide
What class of drug is Amiodarone?
3
What is the effect and consequence of Amiodarone on K channels?
Blocks, prolongs refractoriness and APD
What is the effect and consequence of Amiodarone on Na channels?
Blocks Na channels that are in the inactivated state
What is the effect and consequence of Amiodarone on Ca channels?
Blocks to slow SA node phase 4
Does amiodarone have a competitive or noncompetitive block on alpha, beta, and M receptor?
Noncompetitive
What are the clinical applications of Amiodarone? (3)
Convert AF
AV node tachycardia
Acute termination of VT or VF
What are the main adverse effects of amiodarone?
DEA (metabolic product) has very high antiarrhythmic potency
rapid redistribution out of heart may lead to early recurrence of arrhythmias
Why is the fact that amiodarone is lipid soluble problematic?
Difficult to determine the [plasma]
What are the side effects of using Amiodarone Iv?
Decreases cardiac contractility and PVR, causing hypotension
What is the most serious side effect of amiodarone?
Lethal interstitial pneumonitis
What are the effect of amiodarone on hyperthyroidism or hypothyroidism?
can cause either via destruction
Inhibit Iodine conversion