<prompt> Answer this question truthfullyHow can cardiac contractility be estimated and what is the parameter used for this estimation?  <response>: <reason> Cardiac contractility, which refers to the ability of the heart to contract and pump blood effectively, can be estimated using a variety of methods. One commonly used parameter for this estimation is the left ventricular ejection fraction LVEF. The LVEF is a measure of the percentage of blood that is ejected from the left ventricle with each heartbeat. A normal LVEF is typically between 50 and 70. A lower LVEF can indicate reduced cardiac contractility, which may be a sign of heart failure or other cardiac conditions. Other methods for estimating cardiac contractility include measuring the stroke volume, cardiac output, and various hemodynamic parameters. 