I. Antiarrhythmics Flashcards
Causes of Cardaiac arrhythmias
- Arterial Hypoxemia
- Electrolyte or Acid-Base Abnormality (Alkalosis, Acidosis, Hypokalemia, Hypomagnesemia)
- Myocardial Ischemia
- Altered Sympathetic Nervous System Activity
- Severe Bradycardia
- Pharmacological Factors
- Idiopathic or Anatomical Variants (RBBB in military, Prior Open Heart Surgery)
Arrhythmia treatment indications:
- No correction after removal of precipitating cause
- Hemodynamic function is compromised
- Disturbance predisposes to a more serious cardiac arrhythmia (VF or VT)
Non-pharmacological Antiarrhythmic Treatments
- chronic arrhythmia patients treated with catheter ablation (often performed under GA in EP lab, lengthy 6-8 hours)
- Pacemaker
- Cardioversion
What happens if too much of heart conduction pathway gets burned during ablation?
Pt will need to be paced
What drug may be used to cardiovert patient ?
Adenosine
will stop heart and allow it to reset
How many phases of action potential
5
What classification is used to classify drugs based on primary mechanism of antiarrhythmic properties?
Vaughn-Williams (5 classes)
- imperfect
- drugs classified based on the action that was first described, NOT necessarily the most therapeutically signifiant MMOA
Class 1a
- description
- indications
- Blocks Na channels
- Slowed conduction by prolongation of AP duration
- Tx if heart is beating too rapidly or in uncoordinated fashion
- Indications:
- SVT
- VTach
- Symptomatic PVCs
- Prevention of Recurrent Afib
Class 1a drugs
Quinidine
Procainamide (Pronestyl)
Disopyramide (Norpace)
Quinidine Indicatoin
Acute & chronic SVT
Quinidine dose
50-75 mg/hr (IV)
Quinidine clinical considerations/effects
- Displace Digoxin from tissue stores (increase levels)
- VD & myocardial depression when rapid push (can get tachy)
- Blocks Na & K
- Prolong QT. & widened QRS
Procainamide indication
VTach & WPW
Procainamide dose
IVP: 10-15 mg/kg
Infusion: 2-6 mg/min
Procainamide causes a high incidence of ____
Hypotension
Disopyramide Indications
- Atrial & Ventricular dysrhythmias
Which class 1a antiarrhythmic has mild antichoinergic side effects?
Disopyramide (Norpace)
Clinical considerations with Disopyramide (Norpace):
- significant myocardial depression
- can precipitate CHF & hypotension
- mild anticholinergic effects
Class 1b
- blocks Na channels
- decreases duration of action potentials & refractories
- do NOT affect QRS
- Tx Ventricular arrhythmias
Class 1b indications
- Vtac
- Symptomatic PVCs
- Prevention of Vfib
Class 1b drugs
- Lidocaine (Cardiac Xylocaine PF)
- Phenytoin (Dilantin)
Lidocaine indication
PVCs & Vtac
Lidocaine Dose
1-2 mg/kg IVP
1-4 mg/min
100mg common dose to knockout run of PVCs, 3-4+, or Vtac
Lidocain clinical considerations
- Fast on/off
- Can decrease AV node conduction
Phenytoin (Dilantin) Indications
- Ventricular Dysrhythmias or Digitals Toxicity
- Mostly used to treat seizures
Phenytoin (Dilantin) dose
100 mg (1.5 mg/kg) q. 5 min
Phenytoin (Dilantin) clinical considerations
- CNS S/E
- Mostly used to treat seizures: Cyt P450 inducer - metabolizes NMB quickly