What does it mean when a regular tilt table test is normal but you crash on one with isuprel? Bp and hr tanked, saw spots, shivering cold, and nauseous

Vasovagal syncope. The test results suggest that the body's automatic nervous system overcompensates for the stimulus of the isuprel, a drug that speeds up the heart. The overcompensation slows the heart too much and lowers the blood pressure and there is syncope (fainting) or almost fainting. This called neurocardiogenic syncope or vasovagal syncope. There are several drug treatments.