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Unit 4 Pharm - Arrythmia
Agents for treatment of arrythmias
26
Pharmacology
Professional
12/14/2011

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Term
Bradyarrythmias
Definition

Impulse initiation: Sinus arrest, sinus bradycardia, sinoatrial exit block.

Impulse conduction: Heart block (Types I, II, III)

Term
Tachyarrythmias
Definition

1) Increased automaticity (impulses come from somewhere other than sinus node). EXAMPLES: Atrial Tachycardia - abnormal pulses coming from the atria. Junctional tachycardia - abnormal AV pulses.

Ventricular tachycardia - abnormal pulses coming from ventricle.

2) Triggered activities in phase 3 or 4 (repolarization). EXAMPLES: Early afterdepolarization (EAD) - interrupts phase 3. Delayed afterdepolarization (DAD) - interrupts phase 4 of AP.

3) Impulse conduction through tissues with different conductivities causing reentry circuit.

Term
Increased automaticity
Definition

Atrial Tachycardia - abnormal pulses coming from the atria.

Junctional tachycardia - abnormal AV pulses.

Ventricular tachycardia - abnormal pulses coming from ventricle.

Term
Triggered
Definition
Term
Wolff Parkinson White
Definition

Cells with conduction properties remain around tricuspid and mitral annuli during development. Conduction to ventricular tissue is faster than AV node.

Look for Delta Wave on EKG.

Term
Atrial Flutter
Definition

Reentry circuit around mitral, tricuspid annulus.

Fast, but regular ventricular response.

Atrial rate is ~300 bpm.

Sawtooth pattern.

Term
Atrial fibrillation
Definition
RR (ventricular) interval is irregularly irregular with no organized p impulse.
Term
Mechanism of arrythmia.
Definition

NEED: 1) substrate - scar tissue, slow/fast pathway.

2) trigger - electrolyte imbalance, acid/base imbalance.

Term
Bradyarrythmia
Definition
TREATMENT: Treat underlying cause (drugs, high vagal tone) if possible. If not, use pacemaker.
Term
Vaughan Williams Classification System
Definition

Primarily Sodium Channel Blockers:

1a) Quinidine, procainamide, disopyramide.

1b) Lidocaine, mexiletine, tocainide.

1c) Flecainide, propafenone.

 

2) Beta blockers

 

3) K channel blockers

Amiodarone, bretylium, sotalol, ibutilide, dofetilide.

 

4) CCBs

Verapamil, diltiazem.

 

NOT CLASSIFIED: Digoxin, Adenosine.

Term
Adenosine
Definition

MECH: Acts on adenosine receptors in atrium, SA node and AV node. Activates outward K flux and inhibition of calcium current causing hyperpolarization which slows automaticity and AV conduction.

USE: Acute termination of supraventricular tachycardia (SVT).

1/2 life only 10 seconds!! Vaugh Williams 0.

 

Term
Procainamide
Definition

MECH: Na channel blocker, prolongs QRS, slowing conduction.

AE: Hypotension, lupus (with long-term treatment), inpatient only.

Metabolized to N-acetlyprocainamide which has class 3 properties (K channel blockade). Vaugh Williams 1a.

Term
Quinidine
Definition

MECH: Blocks Na, K channels and alpha adrenergics.

USE: Atrial fibrillation. Also Brugada's syndrome (Na ion channel mutation) and short QT syndrome (K channel mutation).

AE: Naus., diarrhea, Quinidine syncope (polymorphic v-tach secondary to prolongued QT interval)--monitor patients carefully. Vaugh Williams class 1a.

Term
Disopyramide
Definition

MECH: Direct vagal blocker.

USE: Baseline bradycardia, Ventricular tachycardia.

AE: Urinary retention, blurred vision, exacerbated glaucoma (anticholinergic). Vaugh Williams class 1a.

Term
Lidocaine
Definition

MECH: Na channel blocker. Works preferentially on  ischemic ventricular myocardium.

USE: Ventricular Tachycardia.

AE: neurological: tremor, slurred speach, convulsions and seizure. Metabolized in liver (therefore, IV only)--reduce dose in CHF and liver disease patients. ONLY I.V. Vaugh Williams class 1b.

Term
Mixiletine
Definition

MECH: Oral Lidocaine. Same mech.

USE: Ventricular tachycardia in ischemic tissue. Also for use in patients on drugs that prolong QT interval.

AE: GI upset. Vaugh WIlliams class 1b.

Term
Flecainide
Definition

MECH: Potent Na channel blocker which prolongs atrial refractory time and QRS interval.

USE: Premature Ventricular Contraction (PVC), A-Fib.

CONTRA: DO NOT use in patients with CAD, cardiomyopathies or LV dysfunction.

Vaugh Williams class 1c. 5-hydroxy Propafenone is an active metabolite.

Term
Propafenone
Definition

MECH: Potent Na channel blocker which prolongs atrial refractory time and QRS interval.

USE: Premature Ventricular Contraction (PVC), A-Fib.

CONTRA: DO NOT use in patients with CAD, cardiomyopathies or LV dysfunction.

Vaugh Williams class 1c.

Term
Beta blockers (Class II)
Definition

MECH: Increase refractory time in AV node.

AE: Bronchospasm, bradycardia.

Term
Amioderone
Definition

MECH: Blocks, K, Na, Ca and Beta receptor.

USE: Ventricular arrythmia, A-Fib.

AE: Thyroid imbalance (contains iodine), hypotension due to vasodilation. Liver, lung toxicity as well.

All 4 class actions but considered class III.

Term
Dronedarone
Definition

MECH: Like Amioderone but more tolerable due to its lack of iodine.

USE: A Fib (NOT effective in LV dysfunction).

Class III.

Term
Sotalol
Definition

MECH: K channel blocker which prolongs Ventricular action potential (APD), prolongs Effective refractory period (ERP). Also a beta blocker.

USE: Ventricular and atrial arrythmias.

Renally adjust dosage. Class III.

Term
Dofetilide
Definition

MECH: Pure blockage of IKr channel (phase 3).

USE: A-Fib (in hospital only). Can be used for patients with A-fib and ischemic cardiomyopathy and CAD.

Potential for developing Toursades so watch QT closely.

Term
Ibutilide
Definition

MECH: IKr blocker, also activates inward Na current.

USE: Atrial flutter, Atrial Fibrillation (ONLY I.V.).

AE: 4% develop Torsades--watch carefully for 4 hrs.

Term
Verapamil
Definition

MECH: L-type Ca channel blocker. Slows impulse in SA and AV node by increasing conduction time and increasing refractory time.

USE: SVT

AE: Negative inotrope (watch in HF), sinus arrest, AV block.

Term
Diltiazem
Definition

MECH: L-type Ca channel blocker. Slows impulse in SA and AV node by increasing conduction time and increasing refractory time.

USE: SVT

AE: Negative inotrope (watch in HF), sinus arrest, AV block.

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