Venous pooling during nitrate-stimulated tilt testing in patients with vasovagal syncope

Aims To investigate the importance of venous pooling and variation in venou s tone during nitrate-stimulated tilt testing in patients. Methods Ten patients with a history of vasovagal syncope underwent an uprig ht tilt test after an injection of Tc-99m-labelled albumin. A gamma camera was positioned at the level of the lower legs. The patients were tilted to 90 degrees for 30 min or until symptoms developed. In those subjects who di d not show any symptoms before the end of the 30-min period, isosorbide din itrate (ISDN) 5 mg was given sublingually and the test was prolonged for a maximum of 15 min. Results Nine of 10 patients needed nitrate stimulation to develop symptoms, and one patient remained symptom free following ISDN administration. Measu rement of radioactivity revealed no significant increase in calf volume aft er nitrate stimulation (the mean volume increase was 77% before ISDN stimul ation and a further 0.9% afterwards). Conclusions The higher sensitivity for vasovagal syncope during upright til t testing after administration of sublingual ISDN is not due to an increase in venous pooling in the lower extremities. (Europace 2000; 2: 343-345) (C ) 2000 The European Society of Cardiology.