While studying for the NCLEX and practicing as a nurse, you will surely come across a medication class called cardiac glycosides.

What are Cardiac Glycosides?

Cardiac glycosides are a class of medications that are derived from plants, used to treat various cardiovascular conditions, including heart failure and certain arrhythmias.

The primary mechanism of action of cardiac glycosides is to increase the force of contraction of the heart muscle. This is accomplished by inhibiting the action of the sodium-potassium ATPase pump, which leads to an increase in the concentration of intracellular sodium. This increase in sodium concentration causes an increase in intracellular calcium, which in turn leads to increased contractility of the heart muscle.

One of the most commonly used cardiac glycosides is digoxin. It is typically prescribed for the treatment of heart failure and certain types of arrhythmias, such as atrial fibrillation. Digoxin can help improve heart function and reduce symptoms such as shortness of breath and fatigue.

The 3 different types of cardiac glycosides include:

1. Inotropes

2. Chronotropes

3. Dromotropes

Inotropes are medications that affect the strength of the heart's contractions. They increase the force of contraction of the heart muscle aka increases the amount of blood pumped out of the heart with each beat. Inotropes can be used to treat conditions such as heart failure and shock, where the heart's ability to pump blood is compromised. Common inotropes include dopamine, dobutamine, and milrinone.

Inotropes may be used in the following situations:

Chronotropes are medications that affect the heart rate. They increase or decrease the heart rate by affecting the electrical impulses that regulate heart rhythm. Chronotropes can be used to manage conditions such as bradycardia (slow heart rate) or tachycardia (fast heart rate). Common chronotropes include atropine, epinephrine, and beta-blockers.

1. Bradycardia: Chronotropes can be used to increase the heart rate in patients with bradycardia, which is a slow heart rate that can cause symptoms such as dizziness, fatigue, and fainting.
2. Tachycardia: Chronotropes can be used to decrease the heart rate in patients with tachycardia, which is a fast heart rate that can cause symptoms such as palpitations, shortness of breath, and chest pain.
3. Heart failure: Chronotropes may be used in combination with inotropes to manage heart failure, which is a condition in which the heart's ability to pump blood is compromised.
4. Anesthesia: Chronotropes may be used during anesthesia to manage heart rate and blood pressure.

In clinical practice, inotropes and chronotropes are often used together to manage cardiac function. For example, in a patient with heart failure and a slow heart rate, a healthcare provider may use both a positive inotrope (such as dobutamine) to increase the heart's contractility and a positive chronotrope (such as epinephrine) to increase the heart rate.

It's important to note that inotropes and chronotropes are potent medications that should be used with caution and under the close supervision of a healthcare provider. They can have significant side effects, and their use requires careful monitoring and adjustment to avoid potential harm to the patient.

Dromotropic drugs are a class of medications that affect the conduction of electrical impulses in the heart. Specifically, they alter the rate at which electrical impulses travel through the AV node, which is a critical part of the electrical conduction system of the heart.

These drugs are often used to treat various cardiovascular conditions, including arrhythmias (irregular heart rhythms) and heart failure. They work by either increasing or decreasing the speed at which electrical impulses travel through the AV node, depending on the specific drug and the desired effect.

For example, drugs that increase the speed of electrical impulses through the AV node are called positive dromotropic drugs. These drugs can be used to treat conditions such as heart block, which is a condition where the electrical signals that control the heartbeat are interrupted.

On the other hand, drugs that decrease the speed of electrical impulses through the AV node are called negative dromotropic drugs. These drugs can be used to treat conditions such as atrial fibrillation, which is an irregular heartbeat that can increase the risk of stroke.

Dromotropic drugs are typically used to treat a variety of cardiovascular conditions, including:

1. Arrhythmias: These are irregular heart rhythms, which can include atrial fibrillation, atrial flutter, and ventricular tachycardia. Positive dromotropic drugs such as isoproterenol and dopamine can be used to increase the speed of electrical impulses through the AV node, which can help treat certain types of arrhythmias.

2. Heart failure: In heart failure, the heart is unable to pump blood effectively. Negative dromotropic drugs such as beta-blockers can be used to slow down the rate at which electrical impulses travel through the AV node, which can reduce the workload on the heart and improve its ability to pump blood.

3. Heart block: This is a condition where the electrical signals that control the heartbeat are interrupted. Positive dromotropic drugs such as atropine and isoproterenol can be used to increase the speed of electrical impulses through the AV node and improve heart function in people with heart block.

4. Supraventricular tachycardia (SVT): This is a condition where the heart beats too quickly due to an abnormal electrical pathway in the heart. Negative dromotropic drugs such as verapamil and diltiazem can be used to slow down the speed of electrical impulses through the AV node and help control the heart rate.

 

Overall, dromotropic drugs are an important class of medications for treating a range of cardiovascular conditions by affecting the electrical conduction system of the heart. The specific type of dromotropic drug used depends on the specific condition being treated and the desired effect.