HEAD-UP TILT TEST IN HEALTHY, ASYMPTOMATI C SUBJECTS

The heap-up tilt test has demonstrated to useful in the study of patie nts with syncope of unknown origin for the diagnosis of neurocardiogen ic syncope. Several publications have described different methods, wit h different results in cases as well as in controls. We performed a pr ospective study in a group of normal subjects in order to evaluate the methodology used in our population and to establish its specificity. A positive test was defined as the presence of syncope or presyncope a nd hypotension. The examination was carried out on a tilt table, five minutes at 0 degrees, then at 70 degrees during 20 min. In the absence of syncope or presyncope an i.v. infusion of isoproterenol was starte d afterwards in order to increase the heart rate 30-50% over the basel ine values and administered during 20 min at 70 degrees. Twenty one vo lunteers (14 male and 7 women; mean age 26.7 +/- 3.5 years; range: 21- 33 years) and body mass index 23.4 +/- 2.2 kg/m(2) were examined. Mean dose of isoproterenol was 3.1 +/- 0.9 mu g/min (3.4 +/- 1.1 in men an d 2.6 +/- 0.7 mu g/min in women, NS). During the phase without isoprot erenol no subject developed hemodynamic alterations neither symptoms. One volunteer (4.8%) developed presyncope and systemic hypotension (52 /28 mm Hg) accompanied with nodal rhythm after 14 min of isoproterenol at 70 degrees, and his examination was discontinued, with immediate r ecovery. Three other subjects developed asymptomatic transient nodal r hythm during the phase with isoproterenol and recovered spontaneously. No other complications were observed. It is concluded that head-up ti lt test with isoproterenol at 70 degrees, with the used doses and hear t rate increments, is highly specific (95%) to establish the diagnosis of a neurocardiogenic syncope.