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Antiarrhythmic therapy: Automaticity
- All cardiac cells have potential to be a pacemaker. Arrhythmia caused by impulses that are NOT initiated by SA node. This impulses are slower, than SA node.
- Ectopic Foci = abnormal point in the heart.EF caused by ischemia, acidosis, supressant drugs.
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Antiarrhythmic therapy: Refractory period + mechanism of action
- RP= responsiveness of the membrane during recovery from previous activity.
- Antiarrhythmic drugs:
- 1) decrease automaticity
- 2) Increase refractory period
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Antiarrhythmic drugs. QUINIDINE
- comes in different salts:
- Quinidine Sulfate - 83%
- Quinidine Glacanate - 62%
- Pharmacology:
- - decrease automaticity and increase refractory period.
- - Never administer IV: dilate vessels -> hypotension -> shock.
- Injectable vial for IM use only.
- - Increase conduction through AV node -> potential for V-fib.
- We use cardiac glycosides as adjunct therapy in order to prevent V-fib (they slow down AV node conduction).
- - Arrhythmogenic
- - Toxicity (Cinchonism);
- tinnitus, headache, nausea/ vomitting, vertigo
- USAGE
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Atrial tachycardia- - A-fib (Use digoxin as adjunct therapy)
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Antiarrhytmic drugs. Procainamide
- 1) Decrease Automaticity and increase RP
- 2) Slow AV conduction (No need in Digoxin)
- Adverse RXN:
- - Lupus-like syndrome (Dose Related, Reversible)
- - Arrhythmogenic
- Use:
- - Atrial tachycardia
- - Atrial fibrilation
- - Ventricular Arrhythmia (IV use when Lidocain fails or contraindicated)
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Antiarrhythmic drugs. Disopyramide
- - decrease automaticity and increase refractory period
- - No effect on AV conduction (no need in Digoxin)
- - Strong anticholinergic (dry mouth, constipation, GI upset)
- Contraindication:
- Heart failure, b/c they increase CO
- USE:
- - Atrial tachycardia
- - Atrial fibrilation
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Antiarrhythmic drugs. Lidocaine
- - local anasthetic
- - antiarrhythmic (IV use only)
- - high therapeutic index (safe)
- Adverse RXN:
- CNS toxicity: tinnitus, respiratory depression, seizure
- Dosing:
- 1) Loading dose
- 2) IV infusion
- USE:
- Ventricular arrhythmias
- Digoxin toxicity arrhythmias
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Mexelitine, Tocainide, Flecainide
- - oral agents for ventricular arrhythmias
- - pharmacology similar to Lidocaine:
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- Lidocaine:
- - local anasthetic
- - antiarrhythmic (IV use only)
- - high therapeutic index (safe)
Adverse RXN: CNS toxicity: tinnitus, respiratory depression, seizure
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Antiarrhythmic. Propranolol
- B-blocker
- IV use as an antiarrhythmic
- Use:
- Atrial tachicardia
- V tachcardia
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Antiarrhythmic. Amiodarone
45 day half life
use: Ventricular Arrhythmia (IV use)
- Adverse reactions:
- cataract
- pulmonary fibrosis
- hypothyroid
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Antiarrhythmic. Verapamil
- Ca++ blocker
- IV push for antiarrhythmic properties
- second dose can be prepared in 5 min (90% effective)
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Antiarrhythmic. Atropine
- Anticholinergic
- IV push for antiarrhythmic use
- Use:
- Sinus bradicardia (slow heart rate)
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