What precaution should be taken when a patient with a pacemaker undergoes an MRI?

When a patient with a pacemaker is scheduled for an MRI, it is essential to take comprehensive precautions to ensure patient safety. Monitoring vital signs closely is important because MRI procedures can affect the function of the pacemaker and potentially cause arrhythmias or other cardiac issues. Disabling the pacemaker is a precaution that may be necessary to prevent it from being affected by the magnetic fields used in an MRI, which could lead to malfunction of the device or patient discomfort. Considering alternatives to MRI, such as CT scans or ultrasound, is prudent in cases where the risks associated with having a pacemaker present during an MRI outweigh the benefits of the imaging.

These measures together represent a holistic approach to patient safety when dealing with individuals who have implantable devices like pacemakers, making 'All of the above' the most comprehensive and appropriate answer. By considering the full scope of required precautions, medical personnel can create a safer environment for patients undergoing MRI procedures.