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

Aims To investigate the importance of venous pooling and variation in venous tone during nitrate-stimulated tilt testing in patients. Methods Ten patients with a history of vasovagal syncope underwent an upright tilt test after an injection of99mTc-labelled albumin. A gamma camera was positioned at the level of the lower legs. The patients were tilted to 90° for 30 min or until symptoms developed. In those subjects who did not show any symptoms before the end of the 30-min period, isosorbide dinitrate (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. Measurement of radioactivity revealed no significant increase in calf volume after nitrate stimulation (the mean volume increase was 77% before ISDN stimulation and a further 0·9% afterwards). Conclusions The higher sensitivity for vasovagal syncope during upright tilt testing after administration of sublingual ISDN is not due to an increase in venous pooling in the lower extremities. [ABSTRACT FROM PUBLISHER]