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Pharmacology [CVS] 14- Cardiac Arrhythmia Treatments [Class 1: Quinidine, Procainamide, Flecainide]

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In the previous lecture we discussed an introduction to cardiac arrhythmia we talked about cardiac myocytes action potential and arrhythmias mechanisms and types so in this lecture we’ll start talking about cardiac arrhythmias drugs the key in the treatment of cardiac arrhythmias is to control the heart rhythm and this is done by increasing the duration of

The action potential slowing conduction velocity and increasing the refractory period or decreasing the sympathetic effect on the heart so they are divided to four major classes according to their mechanism of action class 1 3 and 4 increase the duration of cardiac cells action potential such as sodium channel blockers potassium channel blockers and calcium

Channel blockers and class 2 suppresses the sympathetic effect on the heart and it includes beta blockers many drugs have actions relating to more than one class or may have active metabolites with a different class of action let’s first talk about class one they block voltage-gated sodium channels they decrease automaticity and reduce conduction velocity they

Are used for atrial and ventricular arrhythmias they are subdivided into three subclasses according to their effect on the duration of the ventricular action potential class 1a 1bn1c quinidine is the prototype drug of class 1a other agents in this class include procainamide and disopyramide quinidine binds to open and inactivated sodium channels and prevents

Sodium influx thus slowing the rapid upstroke during phase zero it also inhibits potassium channels and blocks calcium channels because of these actions it slows conduction velocity and increases refractory period quinidine also has mild alpha adrenergic blocking and anticholinergic actions procainamide and isopyramide have actions similar to those are quinidine

However there is less anticholinergic activity associated with procainamide and more with disopyramide so they may produce anticholinergic adverse effects such as dry mouth urinary retention blurred vision and constipation neither procainamide nor disopyramide has alpha blocking activity quinidine is used in the treatment of a wide variety of arrhythmias including

Atrial av junctional and ventricular tachyarrhythmias procainamide is available only in an intravenous formulation and may be used in the treatment of acute atrial and ventricular arrhythmias disopyrimide is used in the treatment of ventricular arrhythmias as an alternative to procainamide or quinidine and may also be used for maintenance of sinus rhythm and

Atrial fibrillation or flutter the second class class 1b these drugs rapidly associate and dissociate from sodium channels so their actions are manifested when the cardiac cell is depolarized or firing rapidly this class include lidocaine and mexilatine they are useful in treating ventricular arrhythmias and the third class class 1c it includes kleckenite and

Propofenone flacanite suppresses phase zero upstroke in perkins and myocardial fibers this causes marked slowing of conduction in all cardiac tissue with a minor effect on the duration of the action potential and refractoriness it also blocks potassium channels leading to increased action potential duration propofenone also slows conduction in all cardiac tissues

But does not block potassium channels flaconide is useful in the maintenance of sinus rhythm in atrial flutter or fibrillation in patients without structural heart disease such as left ventricular hypertrophy heart failure atherosclerotic heart disease as it has a negative inotropic effect and can aggravate chronic heart failure and it is also used in treating

Refractory ventricular arrhythmias use of proporthanone is restricted mostly to atrial arrhythmias rhythm control of atrial fibrillation or flutter and paroxysmal supraventricular tachycardia prophylaxis in patients with av reentrant tachycardias that’s all for this lecture in the next lecture we’ll continue talking about the other three classes subscribe and wait for the next lecture

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Pharmacology [CVS] 14- Cardiac Arrhythmia Treatments [Class 1: Quinidine, Procainamide, Flecainide] By Medical Videos [ ANIMATED ]