Registered Cardiovascular Invasive Specialist (RCIS) Practice Test

What physiological effect does an inotrope have on the heart?

1. It decreases heart rate

2. It increases stroke volume

3. It reduces cardiac output

4. It increases peripheral resistance

The correct answer is: It increases stroke volume

An inotrope is a substance that modifies the force or speed of contraction of muscles, particularly cardiac muscles. When we talk about inotropic agents in the context of the heart, they primarily enhance the contractility of the heart muscle. By increasing contractility, inotropes strengthen the heart's contractions, leading to a more effective pumping action during systole. As a result, this increased contractility contributes to a rise in stroke volume, which is the amount of blood ejected by the heart in one contraction. A higher stroke volume means that more blood is pushed into the circulatory system with each heartbeat, ultimately improving overall cardiac output if the heart rate remains stable. In contrast, options discussing decreased heart rate, reduced cardiac output, or increased peripheral resistance misrepresent the action of inotropes. An inotrope does not typically lead to a lower heart rate or diminished cardiac output; rather, it supports the heart’s ability to pump more effectively. Additionally, while peripheral resistance can influence blood flow, it is independent of the direct effects of inotropic drugs on myocardial contractility. Thus, the correct answer highlights the primary role of inotropes in enhancing stroke volume through increased contractility of the heart muscle.