I think in mine and Johnny's cases, it was "secondary" pulmonary hypertension, meaning it was caused by the valve not working properly. Once the valve was repaired or replaced, the problem was "resolved" as Johnny said.
I'm just remembering that I read up on this when the cardiologist first said I had PH, and it could either be primary or secondary.
I suppose if it is primary, it probably doesn't just go away.