What effect does decreased contractility have on stroke volume (SV)?

Decreased contractility refers to the heart's reduced ability to contract and pump blood effectively. When contractility diminishes, the heart muscle does not contract with the same force, leading to a lower volume of blood being ejected with each heartbeat. This directly correlates with stroke volume, which is the amount of blood pumped from the heart with each contraction.

When contractility decreases, the heart cannot push out as much blood, which naturally results in a decrease in stroke volume. Therefore, the correct understanding here is that decreased contractility leads to a reduction in stroke volume, as the heart's efficiency in pumping is compromised.

Additionally, since stroke volume is a critical component of cardiac output (the total volume of blood the heart pumps in a minute), a decrease in stroke volume would also affect overall cardiac output. Hence, while a decrease in contractility decreases stroke volume, it further impacts cardiac output negatively, aligning with the physiological relationship between these factors.