Leg crossing, muscle tensing, squatting, and the crash position are effective against vasovagal reactions solely through increases in cardiac output

• Published in: Journal of applied physiology (1985) Vol. 99; no. 5; pp. 1697 - 1703
• Main Authors: Krediet, C. T. Paul, de Bruin, Ivar G. J. M, Ganzeboom, Karin S, Linzer, Mark, van Lieshout, Johannes J, Wieling, Wouter
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Am Physiological Soc 01.11.2005; American Physiological Society
• Subjects: Adolescent; Adult; Aged; Aged, 80 and over; Biological and medical sciences; Cardiac Output - physiology; Cardiology; Female; Fundamental and applied biological sciences. Psychology; Humans; Leg - physiology; Legs; Male; Middle Aged; Movement - physiology; Muscle Contraction - physiology; Muscle, Skeletal - physiology; Muscular system; Posture - physiology; Reflexes; Syncope, Vasovagal - physiopathology; Syncope, Vasovagal - prevention & control; Tilt-Table Test; Vascular Resistance - physiology; Vertebrata; muscle pump; Mammalia; Blood volume; Modelflow; Striated muscle; Leg; stroke volume
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.01250.2004

1 Department of Internal Medicine, Academic Medical Center/ University of Amsterdam, Amsterdam, The Netherlands; 2 Department of Medicine, University of Wisconsin, Madison, Wisconsin Submitted 5 November 2004 ; accepted in final form 27 June 2005 Tensing of lower body muscles without or with leg crossing (LBMT, LCMT), whole body tensing (WBT), squatting, and sitting with the head bent between the knees ("crash position," HBK) are believed to abort vasovagal reactions. The underlying mechanisms are unknown. To study these interventions in patients with a clinical history of vasovagal syncope and a vasovagal reaction during routine tilt table testing, we measured blood pressure (BP) continuously with Finapres and derived heart rate, stroke volume, cardiac output (CO), and total peripheral resistance using Modelflow. In series A ( n = 12) we compared LBMT to LCMT. In series B ( n = 9), WBT was compared with LCMT. In series C ( n = 14) and D ( n = 9), we tested squatting and HBK. All maneuvers caused an increase in BP, varying from a systolic rise from 77 ± 8 to 104 ± 18 mmHg ( P < 0.05) in series A during LBMT to a rise from 70 ± 10 to 123 ± 9 mmHg ( P < 0.05) in series B during LCMT. In each maneuver, the BP increase started within 3–5 s from start of the maneuver. In all maneuvers, there was an increase in CO varying from 54 ± 12% of baseline to 94 ± 21% in WBT to a rise from 65 ± 17% to 110 ± 22% in LCMT in series A . No maneuver caused significant change in total peripheral resistance. We conclude that the mechanism underlying the effects of these maneuvers is exclusively an increase in CO. Modelflow; muscle pump; stroke volume Address for correspondence: C. T. P. Krediet, Academic Medical Center/Univ. of Amsterdam, Dept. of Internal Medicine, F4-222, Meibergdreef 9, 1105AZ, Amsterdam, The Netherlands (e-mail: c.t.krediet{at}amc.nl )