Cardiac glycosides

Definition

Cardiac glycosides are a class of medications that increase the force of heart muscle contractions and slow down the heart rate. They are primarily used in the treatment of heart failure and certain types of arrhythmias by enhancing cardiac output and improving symptoms. These compounds work by inhibiting the Na+/K+ ATPase pump, leading to increased intracellular calcium levels, which strengthens cardiac contractions.

5 Must Know Facts For Your Next Test

1. Cardiac glycosides improve cardiac output by increasing the strength of heart contractions, making them essential for patients with heart failure.
2. These drugs also have a calming effect on the heart by slowing down the conduction through the atrioventricular (AV) node, helping with certain arrhythmias.
3. Digoxin is one of the most well-known cardiac glycosides, and it has a narrow therapeutic index, meaning careful monitoring is required to avoid toxicity.
4. Common side effects of cardiac glycosides include nausea, vomiting, and visual disturbances, which can indicate overdose or toxicity.
5. Electrolyte imbalances, particularly low potassium levels, can increase the risk of toxicity when taking cardiac glycosides.

Review Questions

• How do cardiac glycosides enhance heart function in patients with heart failure?
  • Cardiac glycosides enhance heart function primarily by increasing the force of contraction of the heart muscle, which improves cardiac output. They achieve this by inhibiting the Na+/K+ ATPase pump, leading to an increase in intracellular sodium and calcium levels. This mechanism helps patients with heart failure by making the heart more efficient at pumping blood, which can relieve symptoms such as fatigue and shortness of breath.
• What are the risks associated with the use of cardiac glycosides, particularly concerning their therapeutic index?
  • Cardiac glycosides like digoxin have a narrow therapeutic index, meaning there is a small margin between effective doses and toxic doses. This increases the risk of toxicity if not properly monitored. Symptoms of digoxin toxicity can include nausea, vomiting, confusion, and visual disturbances. Healthcare providers must regularly monitor blood levels and electrolytes to manage these risks effectively.
• Evaluate the role of electrolyte balance in the effectiveness and safety of cardiac glycoside therapy.
  • Electrolyte balance is crucial in cardiac glycoside therapy as imbalances can significantly affect drug efficacy and safety. Low potassium levels can increase the risk of digoxin toxicity because they enhance its binding to cardiac tissues. Therefore, monitoring electrolyte levels, particularly potassium and magnesium, is essential for patients on cardiac glycosides. Proper management of these electrolytes helps ensure effective treatment while minimizing potential adverse effects.

Related terms

Digoxin: A specific cardiac glycoside derived from the foxglove plant, commonly used to treat heart failure and atrial fibrillation.

Heart Failure: A condition in which the heart is unable to pump adequately to meet the body's needs, leading to symptoms like fatigue, shortness of breath, and fluid retention.

Arrhythmia: An irregular heartbeat that can result in a range of symptoms, from palpitations to severe complications like stroke or heart failure.