An echocardiogram this morning turned up a P.F.O. (common in about 20% of the population, but implicated in some people's chronic migraines) as well as a faulty valve (it 'collapses in on itself').
Apparently it is quite controvertial at the moment as to whether one should correct the P.F.O. for mere migraines, or wait for something more life-threatening to occur, such as stroke. All very interesting to ponder. It will be interesting to hear what my neurologist suggests.

Anyone else encountering this combination of P.F.O.s and migraines?
~b.w.