Anti arrhythmic agents chapter 45 Flashcards
Describe the automaticity, excitability , conductivity, contractility of the cardiac muscle s
-Automaticity – cells can spontaneously initiate impulse or action potential – pacemaker cells
-Excitability – ion shift – ability to respond to impulse and generate action potential
-Conductivity – able to transmit impulse
-Contractility – how well cell contracts after receiving a stimulus
** Injured/ scarred cells lose excitability **
What is the normal functioning conductivity
Impulse starts in SA node
Transmitted to AV node
Down bundle of His
Purkinje fibers
What is arrhythmias? and what can cause them
Arrhythmias involve changes of rate and rhythm due to automaticity or conduction abnormalities
Causes:
Electrolyte imbalance – Ca, K, Na, Mg
Hypoxia
Structural damage that alters conduction pathway
Acidosis/waste accumulation – renal failure
Other cardiac drugs – pro-arrhythmic
What is the goal of anti-arrhythmic drugs?
Alter heart’s electrical conduction system
Mechanism of action is to reduce automaticity, slow conduction and prolong refractory period( cant respond to any new stimuli)
Goal is to prevent arrhythmias, relieve symptoms, and prolong life
What are indications of anti-arrhythmic drugs?
atrial fibrillation and atrial flutter
decrease ventricular rate and irregularity
may also be used for HTN control
What are different classes of anti-arrhythmic drugs?
Class I – Sodium channel blockers
**lidocaine (Xylocaine)
Class II – Beta blockers
**metoprolol (Lopressor)
Class III – Potassium channel blockers
**amiodarone (Cordarone)
Class IV – Calcium channel blockers
**diltiazam (Cardizem)
What are different classes of sodium channel blockers?
anti-arrhythmic
Class 1a- procainamide (Pronestyl)
Class 1b- **lidocaine (Xylocaine)
Class 1c- flecainide (Tambocor)
What is the therapeutic action of lidocaine (Xylocaine)?
anti-arrhythmic, Class 1b
-Block the movement of sodium into cells of cardiac conduction system
-Slows conduction, prolongs refractory period, decreases automaticity, stabilizes cell membrane
Class Ib drugs depress phase 0 somewhat and shorten the duration of the action potential.
What are the indications of lidocaine (Xylocaine)?
anti-arrhythmic, Class 1b
used for ventricular arrhythmias
Atrial fibrillation, premature atrial & ventricular contractions (PAC’s & PVC’s), V tach
What are the pharmokinetics of lidocaine (Xylocaine)?
anti-arrhythmic, Class 1b
Given IV due to extensive first pass effect, dose reduce with renal dz and rapid onset
Decreases myocardial irritability
What are the adverse effects of lidocaine (Xylocaine)?
anti-arrhythmic, Class 1b
CNS effects – tremors, seizures,dizziness,fatigue
GI effects – n/v, change in taste
CV effects – pro-arrhythmic effects, hypotension, vasodilation, potential for cardiac arrest
What are contras of lidocaine (Xylocaine)?
anti-arrhythmic, Class 1b
Heart block, hypotension, shock
-allergy
What are drug to drug interactions of lidocaine (Xylocaine)?
anti-arrhythmic, Class 1b
Potentiates oral anti-coagulants( increased risk for bleeding )
What is class ll anti-arrythmic?
Beta blockers
What is metoprolol (Lopressor)?
Beta blocker class ll
What are therapeutic actions of metoprolol (Lopressor)?
Beta blocker class ll
Beta blockers inhibit SNS stimulation
decreases rate and contraction
decreases BP, decreases O2 demand