In this section of, we’ll be looking at two types of emergency medications – antidysrhythmics and beta blockers – and whether they’re inotropic, chronotropic, or dromotropic.
Amiodarone is a popular antidysrhythmic medication that has negative chronotropic effects and dromotropic effects. How does this happen?
Antidysrhythmics as a Negative Chronotropic
Antidysrhythmics are considered as a negative chronotropic because they can effectively bring down the heart rate. By targeting the SA node, antidysrhythmic drugs influence the contraction and conduction of electrical impulses. Since amiodarone is a negative chronotropic drug, its purpose is to decrease the electrical impulses coming from the AV node as well.
So, when a client is experiencing a detrimental rhythm, like ventricular fibrillation, the priority is to get them out of that state by providing chemical cardioversion in the form of Amiodarone or antidysrhythmics. After giving Amiodarone, the client will be given subsequent shocks using a defibrillator to restore the heart’s normal rhythm.
The main goal of antidysrhythmics is to decrease the heart rate because when a client has an irregular rhythm, the heart is going so fast.
Antidysrhythmics as a Negative Dromotropic
Since antidysrhythmics are focused on getting the electrical impulses down, they are also considered as negative dromotropic.
On the other hand, antidysrhythmics don’t have inotropic properties.
Beta blockers are non-specific medications that block the beta from the system. Beta blockers are those drugs that end in “-lol.” Some popular generic names are Atenolol and Metoprolol. As for some brand names, Lopressor is a widely known brand, as well as Coreg.
Beta blockers block beta receptors of the heart and lungs. To remember which beta blocker is given to the heart and lungs, you just have to keep in mind that beta 1 refers to the heart because there’s only one heart; while beta 2 is given to the lungs because there are two lungs.
A typical side effect that nurses have to watch-out-for when giving beta blockers to clients is that, aside from being anti-hypertensive drugs, they are also anti-rate drugs. This means that beta blockers are non-specific that even if the intention to give the drug is to block the increased heart rate, the agonists used for breathing are also blocked. Therefore, the client is expected to have decreased respiration.
Beta Blocker as a Negative Chronotropic
Since beta blockers decrease the heart rate, it is considered as a negative chronotropic drug because of the primary goal of decreasing the heart rate.
Beta Blocker as a Negative Dromotropic
On the other hand, beta blockers are also considered as a negative dromotropic because they block electrical conductivity inside the heart, telling it to slow down and stabilizing the electrical impulses; thus steadying the rhythm. This is similar to telling the SA and AV nodes to calm down.
The Different Mechanism of Action
Antidysrhythmics and beta blockers are different regarding the mechanism of action in bringing down the excitability of the electrical impulses which results in bringing down the heart rate.
Antidysrhythmics affect the SA and AV node directly; while beta blockers affect the beta receptors.
So, that’s basically the huge difference between the two drugs, but their goal is similar.
In our next lecture, we’ll be tackling calcium channel blockers and cardiac glycosides (Digoxin). Check it out on our SimpleNursing website and YouTube channel.