Digoxin (Lanoxin) is a cardiac glycoside that is among the oldest medications used for heart failure.
What are its two primary actions?
A.
Positive chronotropy and negative inotropy.
B.
Negative inotropy and negative chronotropy.
C.
Positive inotropy and negative chronotropy.
D.
Positive inotropy and positive chronotropy.
The correct answer and Explanation is :
The correct answer is C. Positive inotropy and negative chronotropy.
Explanation:
Digoxin, also known by its brand name Lanoxin, is a cardiac glycoside used primarily in the management of heart failure and atrial fibrillation. Its therapeutic effects are attributed to two main actions: positive inotropy and negative chronotropy.
- Positive Inotropy: This refers to the increased force of cardiac muscle contraction. Digoxin enhances the heart’s ability to pump blood more effectively by increasing the intracellular calcium concentration in cardiac muscle cells. This improvement in myocardial contractility helps the heart to eject more blood with each contraction, which is particularly beneficial in heart failure where the heart’s pumping efficiency is compromised.
- Negative Chronotropy: This describes a decrease in heart rate. Digoxin exerts this effect by increasing vagal tone (parasympathetic nervous system activity) and decreasing the conduction velocity through the atrioventricular (AV) node. This results in a slower heart rate and reduced atrial fibrillation-related symptoms. The slower heart rate allows more time for ventricular filling, which can be advantageous in managing heart failure.
In summary, Digoxin helps the heart work more efficiently by increasing the strength of contractions (positive inotropy) and by slowing down the heart rate (negative chronotropy). These effects combine to improve cardiac output and symptoms related to heart failure, as well as to manage certain arrhythmias like atrial fibrillation.