Which window is best for evaluating the ball excursion of a Starr-Edwards mitral valve using m-mode technique?

The apical window is the most suitable position for evaluating the ball excursion of a Starr-Edwards mitral valve using M-mode technique. This is due to the anatomy and orientation of the heart as visualized from the apical views, which allows for a clear line of sight to the mitral valve.

When positioned at the apical location, the sonographer can angle the M-mode cursor effectively through the mitral valve, directly capturing the motion of the ball-like prosthetic valve as it opens and closes during the cardiac cycle. This perspective enables precise measurements of valve motion and can help evaluate functional aspects of the valve's performance.

While other windows, like the subcostal or parasternal windows, can provide valuable insights into cardiac structure and function, they may not offer the same optimal angle and alignment necessary for evaluating the specific dynamics of the Starr-Edwards valve, making the apical window the preferred choice for this assessment. The suprasternal window, typically used to examine structures such as the aortic arch, is not ideal for mitral valve evaluation.