Final answer:
In the parasternal long-axis view, the echocardiographer should tilt the probe posteriorly to determine the presence of a perimembranous ventricular septal defect.
Step-by-step explanation:
To determine the presence of a perimembranous ventricular septal defect in the parasternal long-axis view, the echocardiographer should tilt the probe posteriorly.
The parasternal long-axis view is obtained by placing the ultrasound probe on the left or right side of the chest, near the sternum, and angling it towards the heart. Tilted posteriorly, the probe provides a clear visualization of the ventricular septum, allowing the echocardiographer to identify any defects.