A bedside test that matches a change in heart rate with a drop in blood pressure after a patient stands may help doctors diagnose certain degenerative brain diseases, according to new research published in the Annals of Neurology.
The test could enable earlier diagnosis of a group of degenerative brain diseases called synucleinopathies, which include Parkinson’s disease, Lewy Body dementia, and multiple system atrophy. Arising from the abnormal buildup of a protein known as alpha-synuclein in the brain, these conditions damage the nerves that control blood pressure and heart rate.
The study’s lead author, Lucy Norclife-Kaufmann, said: ‘For the first time, we have been able to systematically show that patients whose blood pressure drops after standing up without an accompanying increase in their heart rate may have a synucleinopathy.’
‘By taking a patient’s blood pressure lying flat, then looking at the change in heart rate after the patient stands up, we can provide healthcare providers with clues as to whether or not the patient has this neurodegenerative disease.’
Falling blood pressure after standing, a condition known as orthostatic hypotension, can cause dizziness, lightheadedness and fainting. When orthostatic hypotension is due to impaired activation of nerves that squeeze the blood vessels, the condition is called ‘neurogenic orthostatic hypotension,’ and is a failure of the nervous system.
The researchers identified 402 patients with orthostatic hypotension who had a normal heart rhythm. Of these, 378 were diagnosed with synucleinopathies. Orthostatic hypotension in the remaining 24 patients was determined to be due to non-neurological causes such as overmedication with blood pressure control drugs, anaemia, or dehydration.
The patients had their blood pressure measured while lying on a tilting table, which mimics standing up and exerts a strain on the blood pressure causing it to fall. The researchers found that patients with neurogenic orthostatic hypotension had twice the fall in blood pressure but only one-third of the increase in heart rate than patients with non-neurogenic orthostatic hypotension.