Final answer:
Transducer frequency is the parameter least likely to affect serial left ventricular dimension measurements on M-Mode echocardiography.
Step-by-step explanation:
The parameter least likely to affect serial left ventricular dimension measurements on M-Mode echocardiography is d) Transducer frequency. Factors such as respiration, patient positioning, and transducer position can have significant effects on the measurements by altering the position of the heart in the chest or the angle of the ultrasound beam with respect to the heart structures. The transducer frequency mainly influences the resolution and penetration of the ultrasound, but it does not typically affect the actual dimensions measured in M-Mode echocardiography as long as appropriate settings are used for the heart.