BACKGROUND: In this study, we tested two hypotheses. First, we tested the hypothesis that reflex constriction of the venous capacitance beds in patients with vasovagal syncope is impaired during both subhypotensive lower-body negative pressure. Second, we proposed that splenic venoconstriction may be impaired during exercise in patients with vasovagal syncope. METHODS AND RESULTS: We evaluated 25 patients with vasovagal syncope (age, 45.0 +/- 15.9 years; 12 men, 13 women) and 24 control subjects (age, 41.3 +/- 13.7 years; 16 men, 8 women). A nuclear technique was used to assess changes in forearm venous tone during lower-body negative pressure and in splenic venous volume during cycle exercise. Changes in forearm vascular resistance (FVR) during cycle exercise were assessed with a strain-gauge plethysmography technique. The percentage reduction in unstressed forearm vascular volume during lower-body negative pressure was similar in patients and control subjects (9.0 +/- 8.0% versus 9.7 +/- 5.9%, P=NS). During exercise, splenic venous volume decreased less in patients than in control subjects (15.8 +/- 21.7% versus 42.6 +/- 12.6%, P < .0001). FVR decreased by 2 +/- 32% in patients but increased 108 +/- 90% in control subjects (P < .0001). There was no relation between percentage change in splenic volume and percentage change in FVR during exercise in either patients or control subjects (r= -.06, P=NS and r= -.18, P=NS, respectively). CONCLUSIONS: Patients with vasovagal syncope exhibit a failure of the normal increase in tone in the splenic capacitance bed and in forearm resistance vessels during dynamic exercise. Forearm venous tone increases normally during lower-body negative pressure.
BACKGROUND: In this study, we tested two hypotheses. First, we tested the hypothesis that reflex constriction of the venous capacitance beds in patients with vasovagal syncope is impaired during both subhypotensive lower-body negative pressure. Second, we proposed that splenic venoconstriction may be impaired during exercise in patients with vasovagal syncope. METHODS AND RESULTS: We evaluated 25 patients with vasovagal syncope (age, 45.0 +/- 15.9 years; 12 men, 13 women) and 24 control subjects (age, 41.3 +/- 13.7 years; 16 men, 8 women). A nuclear technique was used to assess changes in forearm venous tone during lower-body negative pressure and in splenic venous volume during cycle exercise. Changes in forearm vascular resistance (FVR) during cycle exercise were assessed with a strain-gauge plethysmography technique. The percentage reduction in unstressed forearm vascular volume during lower-body negative pressure was similar in patients and control subjects (9.0 +/- 8.0% versus 9.7 +/- 5.9%, P=NS). During exercise, splenic venous volume decreased less in patients than in control subjects (15.8 +/- 21.7% versus 42.6 +/- 12.6%, P < .0001). FVR decreased by 2 +/- 32% in patients but increased 108 +/- 90% in control subjects (P < .0001). There was no relation between percentage change in splenic volume and percentage change in FVR during exercise in either patients or control subjects (r= -.06, P=NS and r= -.18, P=NS, respectively). CONCLUSIONS:Patients with vasovagal syncope exhibit a failure of the normal increase in tone in the splenic capacitance bed and in forearm resistance vessels during dynamic exercise. Forearm venous tone increases normally during lower-body negative pressure.
Authors: Matthias Schmitt; Daniel J Blackman; Gordon W Middleton; John R Cockcroft; Michael P Frenneaux Journal: Br J Clin Pharmacol Date: 2002-12 Impact factor: 4.335
Authors: Robert S Sheldon; Blair P Grubb; Brian Olshansky; Win-Kuang Shen; Hugh Calkins; Michele Brignole; Satish R Raj; Andrew D Krahn; Carlos A Morillo; Julian M Stewart; Richard Sutton; Paola Sandroni; Karen J Friday; Denise Tessariol Hachul; Mitchell I Cohen; Dennis H Lau; Kenneth A Mayuga; Jeffrey P Moak; Roopinder K Sandhu; Khalil Kanjwal Journal: Heart Rhythm Date: 2015-05-14 Impact factor: 6.343