AEMCA Practice Exam

What physiological effect does digoxin have on cardiac function?

1. Decreases heart rate

2. Increases myocardial contraction force

3. Inhibits calcium channels

4. Reduces blood pressure

The correct answer is: Increases myocardial contraction force

Digoxin primarily increases the force of myocardial contraction, which is referred to as positive inotropic effect. This is particularly significant in the treatment of conditions like heart failure, where the heart's ability to pump blood effectively is compromised. By enhancing the contraction strength of the heart muscle, digoxin improves cardiac output and can alleviate symptoms associated with heart failure. The mechanism behind this effect involves increasing the availability of calcium ions in the heart muscle cells. Digoxin inhibits the sodium-potassium ATPase pump, leading to an increase in intracellular sodium levels, which indirectly enhances calcium influx during cardiac action potentials. This increased calcium availability results in stronger contractions of the heart. While digoxin can also have effects on heart rate, particularly through its action on the vagus nerve to slow conduction through the AV node, its primary utility and physiological impact on cardiac function lies in its ability to increase myocardial contractility.