How does a negative inotropic agent affect heart function?

A negative inotropic agent is one that decreases the strength of the heart's contractions. By reducing contractility, it consequently leads to a decrease in the force with which the heart pumps blood. Since stroke volume is determined by the amount of blood ejected with each heartbeat, a decrease in contractility directly results in a reduced stroke volume. This means that less blood is being effectively pumped out of the heart with each contraction, which can lead to complications in overall cardiovascular function.

The other choices do not align with the effects of a negative inotropic agent. For instance, an increase in heart rate or contractility would indicate a positive inotropic effect rather than a negative one. Similarly, stating that there is no impact on heart function does not reflect the significant consequences that negative inotropic agents have on cardiac performance and output. Therefore, the correct understanding of the impact of negative inotropic agents is that they indeed lead to a decrease in stroke volume, affecting the efficiency of cardiac output.