{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,23]],"date-time":"2026-01-23T08:47:03Z","timestamp":1769158023878,"version":"3.49.0"},"reference-count":30,"publisher":"BMJ","issue":"11","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Heart"],"published-print":{"date-parts":[[2008,11]]},"abstract":"<jats:sec>\n                  <jats:title>Objective:<\/jats:title>\n                  <jats:p>To analyse the influence of breathing activity on cerebrovascular dynamics during presyncope.<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>Design:<\/jats:title>\n                  <jats:p>Retrospective study.<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>Setting:<\/jats:title>\n                  <jats:p>University hospital.<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>Patients:<\/jats:title>\n                  <jats:p>38 subjects developing neurocardiogenic syncope (syncope group), and 61 age-matched control subjects with negative tilt.<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>Interventions:<\/jats:title>\n                  <jats:p>Middle cerebral artery mean blood flow velocity (MCFV), continuous non-invasive blood pressure (BP), end-tidal CO<jats:sub>2<\/jats:sub> (CO<jats:sub>2<\/jats:sub>-et) and minute ventilation were measured before and during 45\u2032 60\u00b0 tilting.<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>Main outcome measures:<\/jats:title>\n                  <jats:p>Respiratory and cerebrovascular variability, cerebrovascular resistance (CVR)\u2014absolute and corrected for CO<jats:sub>2<\/jats:sub>-et at 40 mm Hg (CVR-40)\u2014and dynamic cerebrovascular regulation (CVR-dyn: transfer function phase analysis between MCFV and BP), obtained during supine rest (baseline), first 5 minutes of tilt (early tilt), early- and late presyncope (first and second half, respectively, of 4 minutes preceding syncope in syncope group, and equivalent time in controls).<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>Results:<\/jats:title>\n                  <jats:p>Tilting induced a mean (SE) CVR decrease in controls (baseline 1.20 (0.04); late presyncope 1.12 (0.06) mm Hg \u00d7 s\/cm, p&lt;0.05) but not in the syncope group (baseline 1.09 (0.04); late presyncope 1.09 (0.06) mm Hg \u00d7 s\/cm, p\u200a=\u200aNS). However, CVR-40 showed similar reduction in both groups (controls: from 1.15 (0.04) to 0.96 (0.04) mm Hg \u00d7 s\/cm; syncope group: from 1.01 (0.04) to 0.83 (0.04) mm Hg \u00d7 s\/cm, p\u200a=\u200aNS). CVR-dyn of the two groups was also similar (p\u200a=\u200aNS). Respiratory variability increased in the syncope group, from early tilt to late presyncope (p&lt;0.05 or better), preceding hyperventilation and being significantly correlated with an increase in MCFV and BP variability (p&lt;0.01).<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>Conclusions:<\/jats:title>\n                  <jats:p>During presyncope, the development of respiratory instability and hypocapnia impairs MCFV, thus facilitating the onset of syncope despite preserved cerebrovascular regulation.<\/jats:p>\n               <\/jats:sec>","DOI":"10.1136\/hrt.2006.114223","type":"journal-article","created":{"date-parts":[[2007,10,18]],"date-time":"2007-10-18T20:53:55Z","timestamp":1192740835000},"page":"1433-1439","source":"Crossref","is-referenced-by-count":19,"title":["Influence of respiratory instability during neurocardiogenic presyncope on cerebrovascular and cardiovascular dynamics"],"prefix":"10.1136","volume":"94","author":[{"given":"C","family":"Porta","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"G","family":"Casucci","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"S","family":"Castoldi","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"A","family":"Rinaldi","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"L","family":"Bernardi","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"239","published-online":{"date-parts":[[2007,10,18]]},"reference":[{"key":"2025092012254292000_94.11.1433.1","doi-asserted-by":"crossref","first-page":"1157","DOI":"10.1161\/01.CIR.84.3.1157","article-title":"Cerebral vasoconstriction during head-upright tilt-induced vasovagal syncope: a paradoxic and unexpected response.","volume":"84","author":"Grubb","year":"1991","journal-title":"Circulation"},{"key":"2025092012254292000_94.11.1433.2","doi-asserted-by":"crossref","first-page":"1794","DOI":"10.1161\/01.STR.26.10.1794","article-title":"Simultaneous cerebrovascular and cardiovascular responses during presyncope.","volume":"26","author":"Bondar","year":"1995","journal-title":"Stroke"},{"key":"2025092012254292000_94.11.1433.3","doi-asserted-by":"crossref","first-page":"1564","DOI":"10.1161\/01.STR.28.8.1564","article-title":"Cerebrovascular and cardiovascular measurements during neurally mediated syncope induced by head-up tilt.","volume":"28","author":"Schondorf","year":"1997","journal-title":"Stroke"},{"key":"2025092012254292000_94.11.1433.4","doi-asserted-by":"crossref","first-page":"2493","DOI":"10.1152\/jappl.2001.91.6.2493","article-title":"Dynamic cerebral autoregulation is preserved in neurally mediated syncope.","volume":"91","author":"Schondorf","year":"2001","journal-title":"J Appl Physiol"},{"key":"2025092012254292000_94.11.1433.5","doi-asserted-by":"publisher","DOI":"10.1161\/hc6172.099397"},{"key":"2025092012254292000_94.11.1433.6","doi-asserted-by":"crossref","first-page":"351","DOI":"10.1042\/cs1010351","article-title":"Carbon dioxide, critical closing pressure and cerebral haemodynamics prior to vasovagal syncope in humans.","volume":"101","author":"Carey","year":"2001","journal-title":"Clin Sci (Lond)"},{"key":"2025092012254292000_94.11.1433.7","doi-asserted-by":"publisher","DOI":"10.1161\/01.CIR.0000031798.07790.FE"},{"key":"2025092012254292000_94.11.1433.8","doi-asserted-by":"crossref","first-page":"1195","DOI":"10.1161\/01.STR.28.6.1195","article-title":"Effect of PCO2 changes induced by head-upright tilt on transcranial Doppler recordings.","volume":"28","author":"Cencetti","year":"1997","journal-title":"Stroke"},{"key":"2025092012254292000_94.11.1433.9","doi-asserted-by":"publisher","DOI":"10.1088\/0967-3334\/20\/3\/304"},{"key":"2025092012254292000_94.11.1433.10","doi-asserted-by":"crossref","first-page":"1113","DOI":"10.1152\/jappl.1998.85.3.1113","article-title":"Deterioration of cerebral autoregulation during orthostatic stress: insights from the frequency domain.","volume":"85","author":"Zhang","year":"1998","journal-title":"J Appl Physiol"},{"key":"2025092012254292000_94.11.1433.11","unstructured":"Ewing DJ . 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