Ejection fraction increases with:
**Core Concept**
Ejection fraction (EF) is a critical measure of cardiac performance, representing the percentage of blood ejected from the left ventricle with each heartbeat. It is an essential parameter in assessing heart function, particularly in patients with heart failure or cardiomyopathy.
**Why the Correct Answer is Right**
The correct answer is related to the concept of contractility, which is the intrinsic ability of the myocardium to generate force and shorten during contraction. An increase in contractility leads to a more forceful contraction of the heart muscle, resulting in a greater ejection fraction. This is achieved through the activation of the contractile apparatus, including the troponin-tropomyosin complex, which interacts with calcium ions to facilitate muscle contraction.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is likely incorrect as it does not directly relate to a known factor that increases ejection fraction. It is possible that it was intended to be a distractor related to another cardiac parameter.
**Option B:** This option is also incorrect as it may refer to a condition or medication that can actually decrease ejection fraction, such as heart failure with reduced ejection fraction (HFrEF) or beta-blockers.
**Clinical Pearl / High-Yield Fact**
A key factor that increases ejection fraction is an increase in contractility, which can be achieved through medications such as dobutamine or milrinone. These medications work by increasing the intracellular concentration of calcium ions, leading to a more forceful contraction of the heart muscle.
**Correct Answer:** C. Increased contractility.