Infant murmur - teen issues

My 16 year old son had a heart murmur identified at birth.  We were told that it closed before his first birthday.  In 8th grade he fainted and then subsequently began to get what was labeled as migraine headaches after strenuous exercise.  This went on for 3 years with only occasional migraines.  This past spring he began to really increase his basketball regime and got more migraines.  An EKG was done but was read as normal.  This fall he really increased his exercise and began to be extremely fatigued. He got a migraine and took a new triptan - Axert. He developed blurred vision, eyes crossing and lightheadedness (sometimes all the time, but always on rising in the morning or standing after sitting).  The docs felt the new symptoms were an intractable migraine variant and told him to take a double dose of Axert.  He got worse.  He had a short cardio appointment where the doctor told him to drink more and he was cleared for all activities. The doc did say the murmur was still there.  He tried out for basketball and at the end of a two hour very strenuous tryout, he had tunnel vision and then vision that whited out and he was extremely lightheaded and wobbly.  I took him to the ER where they ran some tests.  He did a cardio stress test the next day and went far into the 5th level and then got lightheaded and they stopped the test.  At that point the techs could not get a reading on his bp, but finally after 5 mins of rest they got a reading of 240/60.  The cardiologist called me the next day and said that while this did raise some eyebrows it was completely normal.  So we were sent back to neuro who then said we should go back to cardio.  He is orthostatic on rising and has been for this whole 3 month time.  He is too lightheaded to go to school and gets very fatigued with any activity.  It is very hard to rouse him in the morning and he has some cognitive issues with this related to language and speaking.
Could his murmur have "reopened" or something?  No one will answer my questions here.  We have another cardio appt with a new doc, but not for 3 more weeks.
Thanks!