Title
Sublingual nitroglycerin used in routine tilt testing provokes a cardiac output-mediated vasovagal response
Author
Gisolf, J.
Westerhof, B.E.
van Dijk, N.
Wesseling, K.H.
Wieling, W.
Karemaker, J.M.
TNO Industrie
Publication year
2004
Abstract
Objectives We set out to determine the effect of sublingual nitroglycerin (NTG), as used during routine tilt testing in patients with unexplained syncope, on hemodynamic characteristics and baroreflex control of heart rate (HR) and systemic vascular resistance (SVR). Background Nitroglycerin is used in tilt testing to elicit a vasovagal response. It is known to induce venous dilation and enhance pooling. Also, NTG is lipophilic and readily passes cell membranes, and animal studies suggest a sympatho-inhibitory effect of NTG on circulatory control. Methods Routine tilt testing was conducted in 39 patients with suspected vasovagal syncope (age 36 ± 16 years, 18 females). Patients were otherwise healthy and free of medication. Before a loss of consciousness set in, oncoming syncope was cut short by tilt-back or counter-maneuvers. Finger arterial pressure was monitored continuously (Finapres). Left ventricular stroke volume (SV) was computed from the pressure pulsations (Modelflow). Spontaneous baroreflex control of HR was estimated in the time and frequency domains. Results During tilt testing, 22 patients developed presyncope. After NTG administration but before presyncope, SV and cardiac output (CO) decreased (p < 0.001), whereas SVR and HR increased (p < 0.001) in all patients. Arterial pressure was initially maintained. Baroreflex sensitivity decreased after NTG. On Cox regression analysis, the occurrence of a vasovagal response was related to a drop in SV after NTG (hazard ratio 0.86, p = 0.005). Conclusions The cardiovascular response to NTG is similar in vasovagal and non-vasovagal patients, but more pronounced in those with tilt-positive results. The NTG-facilitated presyncope appears to be CO-mediated, and there is no evidence of NTG-induced sympathetic inhibition.
Subject
Baroreflex sensitivity
Cardiac output
Diastolic arterial pressure
Heart rate
Interbeat interval
Nitric oxide
Sodium nitroprusside
Stroke volume
Systolic arterial pressure
Glyceryl trinitrate
Cardiovascular response
Cardiovascular system
Diagnostic procedure
Hemodynamics
Pressoreceptor reflex
Vagus reflex
Vein dilatation
Cardiac Output
Nitroglycerin
Proportional Hazards Models
Tilt-Table Test
Vascular Resistance
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TNO identifier
280219
Publisher
Elsevier, Amsterdam
ISSN
0735-1097
Source
Journal of the American College of Cardiology, 44 (3), 588-593
Document type
article