What Causes Low Blood Pressure Levels Upon Standing?

These are my concerns that I would like your help with: 1. My BP varies between 220 and 90 but it is usually 140-165. I have a BP drop of 40-50 points when I stand. This problem has been recurrent for 21 months. The cardiologist told me I have dysautonomia and should have more tests. What additional tests do you think might be helpful? What is the cause of dysautonomia, if that is indeed what I have? 2. My husband died of a sudden heart failure on April 1, 2015 and my first stroke was on May 1, 2015 (stress-induced?). I have had recurrent strokes/TIAs since then. I had MRI-documented strokes in April 2015, July 2015, October 2015 in the left basal ganglia, left centrum semiovale, right cerebellum, and left posterior limb internal capsule. I have stenosis of the right A1 segment, the proximal left A1 segment, the left P2/P3 segment, the bilateral M1 segments, and the distal basilar artery. I have had 20+ TIAs occurring every 2 weeks to 3 months since the first stroke. What is the cause of my multiple strokes, TIAs and stenoses? Each time I think it is the last, and then it happens again. 3. I have had frequent vasovagal attacks after each of my previous strokes/TIAs and each time they did eventually stop (until the next time). For your review, below are all my most recent test results: LABORATORY STUDIES: Sodium 143, potassium 3.7, chloride 111, CO2 of 25.3, BUN 13, creatinine 0.78, glucose 105, A1c 6.0, and magnesium 2.22. TSH 2.438. Troponin is negative. Total cholesterol 246, LDL 156, HDL 66. Triglycerides 121. WBC 6.9, hemoglobin 13.7, and hematocrit 40.2. STRESS TEST Max HR: 134 BPM 86% of Pred: 155 BPM Max BP: 181/083 mmHG Max Work Load: 8.1 METS Exercise ThalliumN Stress done for 5:29 min. Peak HR-133. Sestamibi 33 mci injected during exercise, her legs felt too weak to walk to bed, her mind felt foggy. Myocardial Perfusion Scan Nuc Med Left ventricular size is within normal limits. There is moderate soft tissue and bowel attenuation artifact. The stress tomographic images demonstrate a normal pattern of perfusion. The resting tomographic images demonstrate a similar pattern. There is no evidence for reversible ischemia. Wall motion is normal. The ejection fraction is calculated at 79%. MRA Angio Head There is evidence of intracranial atherosclerotic disease with areas of mild to moderate stenosis, most pronounced in the proximal A1 segment of the right anterior cerebral artery where there appears to be severe stenosis. There is also moderate stenosis within the distal basilar artery, where there is an estimated 50% stenosis. MRI Brain Mild-moderate chronic microvascular disease. Chronic lacunar infarcts involving the left basal ganglia, left centrum semiovale, right cerebellum, and left posterior limb internal capsule. CTA OF THE BRAIN: Severe focal stenosis of the right A1 segment, mild stenosis of the proximal left A1 segment, mild narrowing of the left P2/P3 segment, mild to moderate multifocal narrowings the bilateral M1 segments, and severe focal narrowing of the distal basilar artery is similar to prior. No proximal large vessel occlusion is seen. The bilateral intracranial ICA and right PCA are patent. CTA OF THE NECK: Tortuosity of the proximal internal carotid arteries with abrupt turns identified. No evidence of a hemodynamically-significant stenosis or vessel dissection of the bilateral common carotid, bilateral internal carotid, or bilateral vertebral arteries. Degenerative changes of the spine. CT HEAD Patchy hypoattenuation of the cerebral white matter is most consistent with mild chronic microvascular ischemic changes. Chronic left basal ganglia lacunar infarct. Atherosclerotic calcifications of the cavernous segments of the internal carotid arteries are seen. The ventricles are stable size.