Foreshortening
Foreshortening refers to a situation where the ultrasound plane does not cut through the true apex. You can recognize this phenomenon when the apical region looks "rounded". However, if echocardiography is performed correctly, the apical region should have a bullet-shape. Look out for it and realize the limitations of the images at hand.
Recommended articles:
Jet Direction and the Mechanism of Mitral Regurgitation
Introduction to the Apical Window
The Apical Window & the Four Chamber View
Ischemic Cardiomyopathy: Entire Echo Exam