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Group 2: Beta Blockers – Antiarrhythmic Drugs

by Pravin Shukle, MD
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    00:01 Let's move on to the class 2 drugs. So, these are beta blockers.

    00:04 Now, all beta blockers have a very complex interaction with the membrane.

    00:09 First of all, all beta blockers do have anti-ischemic effects.

    00:13 They reduce the myocardial oxygen demand by reducing heart rate for example.

    00:18 Some beta blockers also have membrane stabilizing effects at the phase 0 point of the action potential.

    00:26 All of the beta blockers will also affect the slow current. So, there is going to be an action on repolarization as well.

    00:34 And there is one beta blocker, it's sotalol, that has action potential prolongation, because in a way, it's acting like a class III antiarrhythmic.

    00:45 Although sotalol is a beta blocker, I'm going to discuss it in the class III discussion.

    00:52 So, in terms of these beta blockers, let's talk about the prototypical antiarrhythmic beta blocker, esmolol.

    00:59 Now, esmolol is particularly useful because it can be given intravenously and it's quite fast acting and relatively short acting.

    01:07 It reduces the cyclic AMP levels. It reduces the sodium current and it reduces the calcium current.

    01:14 The actions are specific to the atrioventricular node.

    01:18 In terms of the ECG changes with these medications, you often will see a prolongation of the PR interval, which represents the conduction through the AV node being delayed.

    01:30 We call that dromotropy. So, esmolol and other beta blockers are negative dromotropic agents.

    01:37 The word "dromos" refers to the Greek god or the patron god of racing.

    01:43 So, dromos means race or fast. So, if you have negative dromotropy, you have a slower speed of conduction.


    About the Lecture

    The lecture Group 2: Beta Blockers – Antiarrhythmic Drugs by Pravin Shukle, MD is from the course Cardiovascular Pharmacology.


    Included Quiz Questions

    1. Some beta blockers have membrane stabilizing effects at the phase 0 portion of the action potential, and will act like Class 1 anti-arrhythmic agents.
    2. All beta blockers will increase myocardial oxygen demand.
    3. All beta blockers will increase the slow current in the action potential.
    4. Sotalol is a unique beta blocker that will shorten the action potential.
    1. ...has actions that are specific to the AV node.
    2. ...increases the sodium current of the cardiac myocyte.
    3. ...incresases the calcium current of the cardiac myocyte.
    4. ...shortens the PR interval.

    Author of lecture Group 2: Beta Blockers – Antiarrhythmic Drugs

     Pravin Shukle, MD

    Pravin Shukle, MD


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