Abstract
OBJECTIVE—To investigate the haemodynamic effects of varying the angle of head up tilt. METHODS—20 healthy subjects (12 female, eight male; mean (SD) age 33.6 (8.4) years) underwent head up tilt for five minutes to each of four angles of tilt in random order, with a five minute rest period at the horizontal between each angle. Forearm blood flow was measured using intermittent occlusion mercury strain gauge plethysmography at two and five minutes. Subjects underwent continuous monitoring of heart rate, systolic blood pressure (SBP), and diastolic blood pressure (DBP) by Finapres and cardiac output and stroke volume by impedance cardiography. Each variable was measured at two and five minutes, averaged over the period of blood flow measurement. RESULTS—Every haemodynamic variable at each angle was significantly different from supine values. Head up tilt produced progressive increases in heart rate (11-21%), SBP (12-21%), and DBP (20-33%) with increasing tilt angle. However, although 45° produced significantly less haemodynamic effect, there were no significant differences for angles between 60° and 90°. Cardiac output fell on head up tilt by 17-20% and stroke volume by 28-34%, but increasing tilt angle produced no significant additional reduction in cardiac output and stroke volume because of increases in heart rate and vasoconstriction. CONCLUSIONS—Angles < 60° produce significantly less haemodynamic effects than steeper angles. Increasing tilt angle beyond 60° produces no apparent additional effect on cardiac output or sympathetic tone. Increasing tilt angle beyond 60° confers no additional orthostatic stress and may not affect the sensitivity and specificity of head up tilt testing as previously thought. Sixty degrees of tilt is a more practical angle for support of a syncopal patient and is recommended. Keywords: head up tilt test; vasovagal syncope; thoracic impedance
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- Abi-Samra F., Maloney J. D., Fouad-Tarazi F. M., Castle L. W. The usefulness of head-up tilt testing and hemodynamic investigations in the workup of syncope of unknown origin. Pacing Clin Electrophysiol. 1988 Aug;11(8):1202–1214. doi: 10.1111/j.1540-8159.1988.tb03973.x. [DOI] [PubMed] [Google Scholar]
- Almquist A., Goldenberg I. F., Milstein S., Chen M. Y., Chen X. C., Hansen R., Gornick C. C., Benditt D. G. Provocation of bradycardia and hypotension by isoproterenol and upright posture in patients with unexplained syncope. N Engl J Med. 1989 Feb 9;320(6):346–351. doi: 10.1056/NEJM198902093200603. [DOI] [PubMed] [Google Scholar]
- Benditt D. G., Ferguson D. W., Grubb B. P., Kapoor W. N., Kugler J., Lerman B. B., Maloney J. D., Raviele A., Ross B., Sutton R. Tilt table testing for assessing syncope. American College of Cardiology. J Am Coll Cardiol. 1996 Jul;28(1):263–275. doi: 10.1016/0735-1097(96)00236-7. [DOI] [PubMed] [Google Scholar]
- Dikshit M. B., Banerjee P. K., Rao P. L. Orthostatic tolerance of normal Indians and those with suspected abnormal cardiovascular reflex status. Aviat Space Environ Med. 1986 Feb;57(2):168–173. [PubMed] [Google Scholar]
- Fitzpatrick A. P., Theodorakis G., Vardas P., Sutton R. Methodology of head-up tilt testing in patients with unexplained syncope. J Am Coll Cardiol. 1991 Jan;17(1):125–130. doi: 10.1016/0735-1097(91)90714-k. [DOI] [PubMed] [Google Scholar]
- Fitzpatrick A., Sutton R. Tilting towards a diagnosis in recurrent unexplained syncope. Lancet. 1989 Mar 25;1(8639):658–660. doi: 10.1016/s0140-6736(89)92155-7. [DOI] [PubMed] [Google Scholar]
- Grubb B. P., Kosinski D., Temesy-Armos P., Brewster P. Responses of normal subjects during 80 degrees head upright tilt table testing with and without low dose isoproterenol infusion. Pacing Clin Electrophysiol. 1997 Aug;20(8 Pt 1):2019–2023. doi: 10.1111/j.1540-8159.1997.tb03612.x. [DOI] [PubMed] [Google Scholar]
- Hainsworth R., Al-Shamma Y. M. Cardiovascular responses to upright tilting in healthy subjects. Clin Sci (Lond) 1988 Jan;74(1):17–22. doi: 10.1042/cs0740017. [DOI] [PubMed] [Google Scholar]
- Kapoor W. N., Brant N. Evaluation of syncope by upright tilt testing with isoproterenol. A nonspecific test. Ann Intern Med. 1992 Mar 1;116(5):358–363. doi: 10.7326/0003-4819-116-5-358. [DOI] [PubMed] [Google Scholar]
- Kapoor W. N., Smith M. A., Miller N. L. Upright tilt testing in evaluating syncope: a comprehensive literature review. Am J Med. 1994 Jul;97(1):78–88. doi: 10.1016/0002-9343(94)90051-5. [DOI] [PubMed] [Google Scholar]
- Mark A. L. The Bezold-Jarisch reflex revisited: clinical implications of inhibitory reflexes originating in the heart. J Am Coll Cardiol. 1983 Jan;1(1):90–102. doi: 10.1016/s0735-1097(83)80014-x. [DOI] [PubMed] [Google Scholar]
- Matalon S. V., Farhi L. E. Cardiopulmonary readjustments in passive tilt. J Appl Physiol Respir Environ Exerc Physiol. 1979 Sep;47(3):503–507. doi: 10.1152/jappl.1979.47.3.503. [DOI] [PubMed] [Google Scholar]
- McMichael J., Sharpey-Schafer E. P. CARDIAC OUTPUT IN MAN BY A DIRECT FICK METHOD: Effects of Posture, Venous Pressure Change, Atropine, And Adrenaline. Br Heart J. 1944 Jan;6(1):33–40. doi: 10.1136/hrt.6.1.33. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Natale A., Akhtar M., Jazayeri M., Dhala A., Blanck Z., Deshpande S., Krebs A., Sra J. S. Provocation of hypotension during head-up tilt testing in subjects with no history of syncope or presyncope. Circulation. 1995 Jul 1;92(1):54–58. doi: 10.1161/01.cir.92.1.54. [DOI] [PubMed] [Google Scholar]
- Raviele A., Gasparini G., Di Pede F., Delise P., Bonso A., Piccolo E. Usefulness of head-up tilt test in evaluating patients with syncope of unknown origin and negative electrophysiologic study. Am J Cardiol. 1990 Jun 1;65(20):1322–1327. doi: 10.1016/0002-9149(90)91321-v. [DOI] [PubMed] [Google Scholar]
- Raviele A., Gasparini G., Di Pede F., Menozzi C., Brignole M., Dinelli M., Alboni P., Piccolo E. Nitroglycerin infusion during upright tilt: a new test for the diagnosis of vasovagal syncope. Am Heart J. 1994 Jan;127(1):103–111. doi: 10.1016/0002-8703(94)90515-0. [DOI] [PubMed] [Google Scholar]
- Rea R. F., Thames M. D. Neural control mechanisms and vasovagal syncope. J Cardiovasc Electrophysiol. 1993 Oct;4(5):587–595. doi: 10.1111/j.1540-8167.1993.tb01246.x. [DOI] [PubMed] [Google Scholar]
- Sheldon R., Killam S. Methodology of isoproterenol-tilt table testing in patients with syncope. J Am Coll Cardiol. 1992 Mar 15;19(4):773–779. doi: 10.1016/0735-1097(92)90517-q. [DOI] [PubMed] [Google Scholar]
- Stevens P. M. Cardiovascular dynamics during orthostasis and the influence of intravascular instrumentation. Am J Cardiol. 1966 Feb;17(2):211–218. doi: 10.1016/0002-9149(66)90354-7. [DOI] [PubMed] [Google Scholar]
- Strasberg B., Rechavia E., Sagie A., Kusniec J., Mager A., Sclarovsky S., Agmon J. The head-up tilt table test in patients with syncope of unknown origin. Am Heart J. 1989 Nov;118(5 Pt 1):923–927. doi: 10.1016/0002-8703(89)90225-1. [DOI] [PubMed] [Google Scholar]
- Thorén P. Role of cardiac vagal C-fibers in cardiovascular control. Rev Physiol Biochem Pharmacol. 1979;86:1–94. doi: 10.1007/BFb0031531. [DOI] [PubMed] [Google Scholar]
- Voice R. A., Lurie K. G., Sakaguchi S., Rector T. S., Benditt D. G. Comparison of tilt angles and provocative agents (edrophonium and isoproterenol) to improve head-upright tilt-table testing. Am J Cardiol. 1998 Feb 1;81(3):346–351. doi: 10.1016/s0002-9149(97)00915-6. [DOI] [PubMed] [Google Scholar]
- Wallin B. G., Sundlöf G. Sympathetic outflow to muscles during vasovagal syncope. J Auton Nerv Syst. 1982 Nov;6(3):287–291. doi: 10.1016/0165-1838(82)90001-7. [DOI] [PubMed] [Google Scholar]