THE INFLUENCE OF RESPIRATORY INSTABILITY DURING NEUROCARDIOGENIC PRESYNCOPE ON CEREBRO- AND CARDIOVASCULAR DYNAMICS

Cesare Porta ¹, Gaia Casucci ¹, Stefano Castoldi ¹, Andrea Rinaldi ¹ and Luciano Bernardi ^1*

¹ Universita' di Pavia - IRCCS Ospedale S. Matteo, Italy

^* To whom correspondence should be addressed. E-mail: lbern1ps{at}unipv.it.

Accepted 11 September 2007

Abstract

Objective Analyse the influence of breathing activity on cerebrovascular dynamics during presyncope.

Design Retrospective study

Setting University hospital

Patients Thirty-eight subjects developing neurocardiogenic syncope (syncope group), and 61 age-matched control subjects with negative tilt.

Interventions We measured middle cerebral artery mean blood flow velocity (MCFV), continuous noninvasive blood pressure (BP), end-tidal CO2 (CO2-et) and minute ventilation (VE) before and during 45' 60° tilting.

Main outcome measures Respiratory and cerebrovascular variability, cerebrovascular resistance, absolute (CVR) and corrected for CO2-et at 40 mmHg (CVR-40), and 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).

Results Tilting induced CVR decrease in controls (baseline = 1.20±0.04; late-presyncope = 1.12±0.06 mmHg x s/cm, p<0.05), but not in syncope group (baseline = 1.09±0.04; late-presyncope = 1.09±0.06 mmHg x s/cm, p: ns). However, CVR-40 revealed similar reduction in both groups (controls: from 1.15±0.04 to 0.96±0.04 mmHg x s/cm; syncope group: from 1.01±0.04 to 0.83±0.04 mmHg x s/cm, p: ns). CVR-dyn of the two groups was also similar (p: ns). Respiratory variability increased in syncope group, from early tilt to late-presyncope (p<0.05 or better), preceding hyperventilation and being significantly correlated to an increase in MCFV and BP variability (p<0.01).

Conclusions During presyncope, the development of respiratory instability and hypocapnia impairs MCFV, thus facilitating the onset of syncope despite preserved cerebrovascular regulation.

Keywords: Baroreceptors, Cerebrovascular circulation, Nervous System Autonomic, Syncope, Ventilation

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

Relevant Article

Cardiorespiratory interaction in vasovagal syncope

Resham Baruah, Darrel P Francis, and Richard Sutton
Heart 2008 94: 1372-1373. [Extract] [Full Text] [PDF]

This article has been cited by other articles:

• Thomas, K. N., Cotter, J. D., Galvin, S. D., Williams, M. J. A., Willie, C. K., Ainslie, P. N. (2009). Initial orthostatic hypotension is unrelated to orthostatic tolerance in healthy young subjects. J. Appl. Physiol. 107: 506-517 [Abstract] [Full Text]  
• Nowak, J. A., Ocon, A., Taneja, I., Medow, M. S., Stewart, J. M. (2009). Multiresolution wavelet analysis of time-dependent physiological responses in syncopal youths. Am. J. Physiol. Heart Circ. Physiol. 296: H171-H179 [Abstract] [Full Text]  
• Baruah, R., Francis, D. P, Sutton, R. (2008). Cardiorespiratory interaction in vasovagal syncope. Heart 94: 1372-1373 [Full Text]