hi Bonnie;
I get palpitations too. I don't have a good explanation for it. it always seems like the palpitations follow a bad night with my sleep apnea, which also makes my IIH worse. they have shown at Stanford that during the struggle to breathe at night during sleep disordered breathing, the abnormal pressures in the chest can actually cause the heart to collapse on itself (briefly I imagine). so even though my heart checks out normal, I suspect perhaps it's the sleep apnea that causes the palpitations. the hypoventilation raises intracranial pressure and makes IIH worse too. but lately I am wondering if there is something else going on, like pressure on the heart centers in the brainstem.
I'm so sorry about your troubles. I would think your neurologist should be able to do the LP; I'd call his office to ask what they want you to do. if you feel awful you can go to the ER; the ER doc should also be able to do it. but only the interventional radiologists can do it under fluoroscopy, so it's just not as finessed without that.
Deb