Decrease in cardiac output and muscle sympathetic activity during vasovagal syncope.

The importance of cardiac output (CO) to blood pressure level during vasovagal syncope is unknown. We measured thermodilution CO, mean blood pressure (MBP), and leg muscle mean sympathetic nerve activity (MSNA) each minute during 60 degrees head-up tilt in 26 patients with recurrent syncope. Eight patients tolerated tilt (TT) for 45 min (mean age 60 +/- 5 yr) and 15 patients developed syncope during tilt (TS) (mean age 58 +/- 4 yr, mean tilt time 15.4 +/- 2 min). In TT patients, CO decreased during the first minute of tilt (from 3.2 +/- 0.2 to 2.5 +/- 0.3 l x min(-1) x m(-2), P = 0.001) and thereafter remained stable between 2.5 +/- 0.3 (P = 0.001) and 2.4 +/- 0.2 l x min(-1) x m(-2) (P = 0.004) at 5 and 45 min, respectively. In TS patients, CO decreased during the first minute (from 3.3 +/- 0.2 to 2.7 +/- 0.1 l x min(-1) x m(-2), P = 0.02) and was stable until 7 min before syncope, falling to 2.0 +/- 0.2 at syncope (P = 0.001). Regression slopes for CO versus time during tilt were -0.01 min(-1) in TT versus -0.1 l x min(-1) x m(-2) x min(-1) in TS (P = 0.001). However, MBP was more closely correlated to total peripheral resistance (R = 0.56, P = 0.001) and MSNA (R = 0.58, P = 0.001) than CO (R = 0.32, P = 0.001). In vasovagal reactions, a progressive decline in CO may contribute to hypotension some minutes before syncope occurs.

[1]  J Van Goudoever,et al.  Continuous stroke volume monitoring by modelling flow from non-invasive measurement of arterial pressure in humans under orthostatic stress. , 1999, Clinical science.

[2]  J. Dhainaut,et al.  Continuous cardiac output and mixed venous oxygen saturation monitoring. , 1998, Journal of critical care.

[3]  H Ikram,et al.  Autonomic control of vasovagal syncope. , 1998, The American journal of physiology.

[4]  D L Eckberg,et al.  Vagal and sympathetic mechanisms in patients with orthostatic vasovagal syncope. , 1997, Circulation.

[5]  P. Marik,et al.  A comparison of hemodynamic parameters derived from transthoracic electrical bioimpedance with those parameters obtained by thermodilution and ventricular angiography. , 1997, Critical care medicine.

[6]  R Furlan,et al.  Sympathetic and baroreceptor reflex function in neurally mediated syncope evoked by tilt. , 1997, The Journal of clinical investigation.

[7]  M. Joyner,et al.  Sympathetic withdrawal and forearm vasodilation during vasovagal syncope in humans. , 1997, Journal of applied physiology.

[8]  D. Kosinski,et al.  Tilt Table Testing: Concepts and Limitations , 1997, Pacing and clinical electrophysiology : PACE.

[9]  D. Benditt,et al.  Neurally Mediated Syncopal Syndromes: Pathophysiological Concepts and Clinical Evaluation , 1997, Pacing and clinical electrophysiology : PACE.

[10]  V. Novak,et al.  Is the heart "empty' at syncope? , 1996, Journal of the autonomic nervous system.

[11]  J. Tyberg,et al.  Abnormal reflex venous function in patients with neuromediated syncope. , 1996, Journal of the American College of Cardiology.

[12]  M. Frenneaux,et al.  Failure of reflex venoconstriction during exercise in patients with vasovagal syncope. , 1996, Circulation.

[13]  S. Su,et al.  Excessive myocardial contraction in vasovagal syncope demonstrated by echocardiography during head‐up tilt test , 1996, Clinical cardiology.

[14]  F. Jaeger,et al.  Changes in left ventricular volume during head-up tilt in patients with vasovagal syncope: an echocardiographic study. , 1996, American heart journal.

[15]  R. Hainsworth,et al.  Relationship between plasma volume, carotid baroreceptor sensitivity and orthostatic tolerance. , 1995, Clinical science.

[16]  H.H. Sun,et al.  An advanced signal processing technique for impedance cardiography , 1995, IEEE Transactions on Biomedical Engineering.

[17]  S. Deshpande,et al.  Comparison of cardiac pacing with drug therapy in the treatment of neurocardiogenic (vasovagal) syncope with bradycardia or asystole. , 1993, The New England journal of medicine.

[18]  A. Muir,et al.  Lack of variation in venous tone potentiates vasovagal syncope. , 1992, British heart journal.

[19]  D. Eckberg,et al.  The vasovagal response. , 1991, Clinical science.

[20]  M Akhtar,et al.  Echocardiographic demonstration of decreased left ventricular dimensions and vigorous myocardial contraction during syncope induced by head-up tilt. , 1991, Journal of the American College of Cardiology.

[21]  R. Hainsworth,et al.  Cardiovascular reflex responses in patients with unexplained syncope. , 1989, Clinical science.

[22]  C. Rothe,et al.  Physiology of venous return. An unappreciated boost to the heart. , 1986, Archives of internal medicine.

[23]  P. Fahey,et al.  Clinical experience with continuous monitoring of mixed venous oxygen saturation in respiratory failure. , 1984, Chest.

[24]  A. Vallbo,et al.  Somatosensory, proprioceptive, and sympathetic activity in human peripheral nerves. , 1979, Physiological reviews.

[25]  U. Freyschuss,et al.  The mechanism of orthostatic and haemorrhage fainting. , 1977, Scandinavian journal of clinical and laboratory investigation.

[26]  F. Abboud.  Control of the various components of the peripheral vasculature. , 1972, Federation proceedings.

[27]  S. Yang.  From cardiac catheterization data to hemodynamic parameters , 1972 .

[28]  J. A. Bowers,et al.  Hemodynamic effects of graded hypovolemia and vasodepressor syncope induced by lower body negative pressure. , 1968, American heart journal.

[29]  S. Epstein,et al.  Role of the Capacitance and Resistance Vessels in Vasovagal Syncope , 1968, Circulation.

[30]  F. Abboud,et al.  Vascular responses after alpha adrenergic receptor blockade: I. Responses of capacitance and resistance vessels to norepinephrine in man. , 1968, The Journal of clinical investigation.

[31]  P. Stevens,et al.  Cardiovascular dynamics during orthostasis and the influence of intravascular instrumentation. , 1966, The American journal of cardiology.

[32]  N. Browse,et al.  Response of capacity vessels in human limbs to head-up tilt and suction on lower body. , 1966, Journal of applied physiology.

[33]  G. Glick,et al.  Hemodynamic changes during spontaneous vasovagal reactions. , 1963, The American journal of medicine.

[34]  E. Lippschutz,et al.  Hemodynamics of idiopathic orthostatic hypotension , 1961 .

[35]  J. Leonard,et al.  Vasodepressor Syncope: Factors Influencing Cardiac Output , 1957, Circulation.