Year: 2023
Type: dissertation
Study design: Observational Study
Abstract: Background: Autonomic nervous system (ANS) dysfunction may lead to orthostatic intolerance (OI) and syncope.Vasovagal syncope (VVS) is the most common cause of syncope whereas orthostatic hypotension (OH) is the most common cause of OI in elderly persons.Still, much remains unknown about the pathophysiology of VVS and OH.Cardiovascular autonomic testing (CAT) including head-up tilt (HUT) can be used to reveal ANS dysfunction as syncope aetiology and study pathophysiology.Patients: The SYSTEMA study (n=3029) included patients with OI and unexplained syncope investigated by CAT in the syncope unit at Skåne University Hospital Malmö.Aims and methods: Paper I included 161 patients with VVS during drug-free HUT and the impact of cardiovascular neurohormones on susceptibility to VVS was studied.Supine and orthostatic plasma concentrations of epinephrine, norepinephrine and prohormone peptides of vasopressin, endothelin, atrial natriuretic peptide and adrenomedullin were analysed in relation to time from tilt-up to onset of VVS.Paper II included 584 patients with classical and delayed OH and clinical characteristics and neurohormones (as in paper I) were compared in the two forms.Paper III included 1928 syncope patients and the influence of age at first syncope on clinical characteristics and final HUT diagnosis was assessed.Paper IV included 2663 syncope patients and the predictive value of history and clinical characteristics for unexplained syncope after CAT was investigated.Results and conclusions: Paper I: Susceptibility to VVS was inversely related to age, higher supine blood pressure and adrenomedullin concentration, whereas greater orthostatic increase in epinephrine and vasopressin predicted shorter time to syncope.Paper II: Compared with delayed OH, classical OH patients were older, had pacemaker-treated arrhythmia, lower glomerular filtration rate, pathologic Valsalva test and Parkinson's disease.Classical OH was associated with increased vasopressin and epinephrine during orthostasis, but blunted increase in norepinephrine.Classical OH is associated with more severe abnormalities of neurohormonal and autonomic regulation and is a more advanced form of OH.Paper III: The first-ever syncope incidence had a bimodal lifetime pattern with peaks at 15 and 70 years.The majority of patients aged ≥60 years had only recent syncope and a higher probability of OH and carotid sinus syndrome.In contrast, older patients with life-long syncope duration had a higher probability of VVS and complex syncope (>1 possible cause of syncope ).This study highlights the value of a thorough history in the evaluation of elderly syncope patients.Paper IV: A syncope diagnosis was provided by CAT in 79% of patients.Predictors of negative CAT were older age at first syncope, syncope without prodrome and cardiovascular comorbidities.These are known risk factors for cardiac syncope and patients with inconclusive CAT require further evaluation.
Author: Torabi, Parisa
Language: English
Subfield: Cardiology and Cardiovascular Medicine
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W7008306957