You take your top off and then lie on your left side with your arm above your head, so you end up looking like one of Ingres' Odalisque paintings - although the effect is rather spoilt by the pair of practical trousers.
The nurse uses some gel around the heart area and then a probe is run over the skin, to get different views of the heart. The only uncomfortable bit was when she pressed into the solar plexus to get a view from that angle, and that was mostly because it came as a surprise. Occasionally the nurse turned on the sound, I guess to get an idea of any abnormal noises. It all sounded a bit strange to me, either like a weaving machine from a cloth mill, or someone running through mud in wellingtons.
There was nothing obviously wrong, but she'll pass the results onto the specialist for a closer look.