Open AccessDecreasing cerebral oxygen consumption during upright tilt in vasovagal syncope
Author(s) -
Medow Marvin S.,
Kothari Mira L.,
Goetz Amanda M.,
O'DonnellSmith Mary Breige,
Terilli Courtney,
Stewart Julian M.
Publication year - 2017
Publication title -
physiological reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.918
H-Index - 39
ISSN - 2051-817X
DOI - 10.14814/phy2.13286
Subject(s) - vasovagal syncope , medicine , transcranial doppler , tilt (camera) , cardiology , cerebral blood flow , anesthesia , syncope (phonology) , mechanical engineering , engineering
We measured changes in transcranial Doppler ultrasound ( TCD ) and near infrared spectroscopy ( NIRS ) during 70° upright tilt in patients with recurrent vasovagal syncope ( VVS , N = 20), postural tachycardia syndrome ( POTS , N = 20), and healthy controls ( N = 12) aged 15–27 years old. VVS was included if they fainted during testing within 5–15 min of upright tilt. We combined TCD and NIRS to obtain estimates of percent change in the cerebral metabolic rate of oxygen consumption ( CMRO 2 ), cerebral blood flow velocity ( CBF v), and oxygen extraction fraction ( OEF ). Over the course of 10 min of upright tilt, CBF v decreased from a baseline of 70 ± 5 to 63 ± 5 cm/sec in controls and 74 ± 3 to 64 ± 3 cm/sec in POTS while decreasing from 74 ± 4 to 44 ± 3 cm/sec in VVS . CMRO 2 was unchanged in POTS and controls during tilt while OEF increased by 19 ± 3% and 15 ± 3%, respectively. CMRO 2 decreased by 31 ± 3% in VVS during tilt while OEF only increased by 7 ± 3%. Oxyhemoglobin decreased by 1.1 ± 1.3 μ mol/kg brain tissue in controls, by 1.1 ± 1.3 μ mol/kg in POTS , and 11.1 ± 1.3 μ mol/kg in VVS . CBF v and CMRO 2 fell steadily in VVS during upright tilt. The deficit in CMRO 2 in VVS results from inadequate OEF in the face of greatly reduced CBF .