10 Questions
Which of the following subclass IA antiarrhythmic preparations is rarely used for supraventricular arrhythmias?
Quinidine
What is the primary indication for IV procainamide in subclass IA?
Hemodynamically stable ventricular tachycardia
What is the mechanism of action of beta-adrenoblocker preparations?
Blockade of myocardial β–adrenergic receptors
Which of the following subclass IB antiarrhythmic preparations is used for chronic treatment of ventricular arrhythmias?
Mexiletine
What is the primary indication for flecainide in subclass IC?
Prophylaxis in paroxysmal atrial fibrillation
What is the effect of beta-adrenoblocker preparations on the SA node?
Slow the rate of the SA node
Which of the following subclass IA antiarrhythmic preparations is used for acute conversion of atrial fibrillation?
Procainamide
What is the effect of beta-adrenoblocker preparations on AV conduction?
Decrease AV conduction
What is the primary indication for lidocaine in subclass IB?
Ventricular arrhythmias
What is the effect of beta-adrenoblocker preparations on automaticity?
Suppress automaticity
Study Notes
Antianginal Effects of Calcium Channel Blockers
- Coronary artery dilatation and relief of coronary spasm (variant angina)
- Decrease myocardial O2 demand due to:
- Arteriolar dilatation, decreasing vascular resistance and afterload
- Decrease in heart rate (HR)
- Decrease in contractility
- Decrease in AV conductivity
Preparations Used to Abolish Angina Pectoris Attacks
- Organic nitrates:
- Nitroglycerin
- Isosorbide dinitrate
- Isosorbide mononitrate
- Trinitrolong
- Nitrong
- Ca channel blocking drugs:
- Nifedipine
- Diltiazem
- Verapamil
- Mibefradil
- K channel activators:
- Minoxidil
- Pinacidil
- Nicorandil
- Diazoxide
- Various drugs:
- Amiodarone
Groups and Preparations Used in Acute Myocardial Infarction
- Opioid drugs:
- Fentanyl
- Morphine
- Trimeperidine
- Anxiolytics:
- Tranquilizers (diazepam)
- Neuroleptics
- Neurolepanalgesia (fentanyl, droperidol or talamonal)
- Prevention of arrhythmias:
- Antiarrhythmics (lidocaine)
- Improvement of circulation:
- Hexamethonium
- Furasemide
- Triperium iodide
- Dopamine
- Norepinephrine
- Phenylephrine
- Prevention of thromboses:
- Anticoagulators (heparin)
- Antiaggregants (fibrinolysine, aspirin)
- Acido-base equilibrium:
- Na bicarbonate
- Dextran 40, 70
- Cardiac failure:
- Cardiotonics (dopamine, glycosides)
- Decrease necrotic area:
- Nitroglycerine
- Amelioration of myocardial metabolism:
- Cardioprotectors (omopatrylate, trimethasidine)
- Antioxidants (coenzyme Q10)
Adenosine
- Based on the influence on the efferent cardiac innervations
- Remedies that stimulate the adrenergic influence:
- β adrenomimetics (izoprenaline)
- Sympathomimetics (ephedrine)
- Remedies with cholinergic influence:
- Anticholinesterases (Edrophonium)
- α adrenomimetics (phenylephrine)
- Remedies that decrease cholinergic action:
- Atropine
Antiarrhythmic Preparations
- Class II – Beta-adrenoblockers:
- Propranolol
- Metoprolol
- Nadolol
- Atenolol
- Acebutolol
- Pindolol
- Sotalol
- Timolol
- Esmolol
- Class III – K+ channel blockers:
- Amiodarone
- Ibutilide
- Bretylium
- Dofetilide
- Sotalol
- Class IV - Ca2+ channel blockers:
- Verapamil
- Diltiazem
- Galapamil
- Nifidifin
- Alinidin
Indications for Antiarrhythmic Preparations
- Subclass IA:
- Supraventricular (atrial) and ventricular arrhythmias
- Quinidine is rarely used for supraventricular arrhythmias
- Oral quinidine/procainamide are used with class III drugs in refractory ventricular tachycardia patients with implantable defibrillator
- IV procainamide used for hemodynamically stable ventricular tachycardia
- IV procainamide is used for acute conversion of atrial fibrillation including Wolff-Parkinson-White Syndrome (WPWS)
- Subclass IB:
- Lidocaine is the drug of choice in emergency treatment of ventricular arrhythmias
- Mexiletine is used for chronic treatment of ventricular arrhythmias associated with previous myocardial infarction
- They are used in the treatment of ventricular arrhythmias arising during myocardial ischemia or due to digoxin toxicity
- They have little effect on atrial or AV junction arrhythmias (because they don’t act on conduction velocity)
- Subclass IC:
- Refractory ventricular arrhythmias
- Flecainide is a particularly potent suppressant of premature ventricular contractions (beats)
- Supraventricular arrhythmias
- Flecainide: Prophylaxis in paroxysmal AF
Mechanism of Action and Antiarrhythmic Effect of Beta-Adrenoblocker Preparations
- Blockade of myocardial β–adrenergic receptors
- Direct membrane-stabilizing effects related to Na+ channel blockade
- Slows SA node and ectopic pacemaking
- Increase refractory period
- Negative inotropic and chronotropic action
- Prolong (decrease) AV conduction (delay)
- Diminish phase 4 depolarization, suppressing automaticity (of ectopic focus)
This quiz assesses the anti-anginal effects of calcium channel blockers, including coronary artery dilation, decreased myocardial O2 demand, and decreased O2 consumption.
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