Mini Review ARTICLE
Cerebral oximetry in syncope and syndromes of orthostatic intolerance
- 1Lund University, Sweden
- 2Department of Clinical Sciences, Faculty of Medicine, Lund University, Sweden
- 3Department of Cardiology, Skåne University Hospital, Sweden
- 4Institute of Cardiology, School of Medicine and Health Sciences, G. D'Annunzio University of Chieti-Pescara, Italy
- 5Institute for Advanced Biomedical Technologies, G. d'Annunzio University of Chieti and Pescara, Italy
- 6National Heart and Lung Institute, Faculty of Medicine, Imperial College London, United Kingdom
- 7Department of Internal Medicine, Skåne University Hospital, Sweden
Cerebral autoregulation is crucial for maintaining cerebral blood flow and perfusion. In recent years, the importance of cerebral oxygenation in syncope and orthostatic intolerance (OI) has received increased attention. Cerebral tissue oxygenation can be measured by using near-infrared spectroscopy (NIRS), which determines the ratio of oxygenated haemoglobin to total haemoglobin in cerebral tissue. NIRS is non-invasive technology using near-infrared light, which displays real-time cerebral tissue oxygenation. Normal values of cerebral tissue oxygenation in healthy subjects are 60 to 80%. Head-up tilt test (HUT) offers the opportunity to observe the haemodynamic changes precipitating syncope and is, today, the standard method for the evaluation of syncope and orthostatic intolerance syndromes. In previous studies where NIRS was applied during HUT, a significant decrease in cerebral tissue oxygenation both prior to and during loss-of-consciousness in vasovagal syncope (VVS) has been observed. Interestingly, cerebral tissue oxygenation appears to decrease even before haemodynamic changes can be observed. Apart from VVS, cerebral tissue oxygenation decreases during orthostatic provocation in patients with orthostatic hypotension (OH) and postural orthostatic tachycardia syndrome (POTS), in the latter even in the absence of hypotension. Importantly, decline of cerebral tissue oxygenation in VVS and POTS during HUT may not correlate with haemodynamic changes. In this mini review, we summarize the current knowledge of the application of cerebral oximetry in syncope and orthostatic intolerance syndromes, discuss its likely value as a clinical diagnostic tool and also emphasize its potential in the understanding of the relevant pathophysiology.
Keywords: tilt test, Orthostatic Intolerance, Syncope, cerebral oximetry, NIRS
Received: 29 Aug 2019;
Accepted: 08 Nov 2019.
Copyright: © 2019 Kharraziha, Holm, Bachus, Ricci, Sutton, Fedorowski and Hamrefors. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: MD. Isabella Kharraziha, Lund University, Lund, Sweden, email@example.com