EFFECT OF PATIENT CHARACTERISTICS ON THE YIELD OF PROLONGED BASE-LINEHEAD-UP TILT TESTING AND THE ADDITIONAL YIELD OF DRUG PROVOCATION

Objective-To define the value of tilt testing and the additional yield of drug provocation over prolonged baseline tilt in different patient subgroups. (Many different protocols are in use for head-up tilt test ing in heterogeneous groups of patients. Not all patients in reported series have recurrent syncope, and there is often a wide age range and a variable incidence of structural heart disease.) Design-In a prospe ctive study, baseline 60 degrees head-up tilt testing was undertaken f or 45 minutes, initially without drug provocation. Patients who remain ed symptom free were given intravenous isoprenaline (isoproterenol) an d further tilting or edrophonium (10 mg bolus) during tilt, in an orde r determined randomly before the start of the test. If they were sympt om free after the first drug, they were given the other drug. A positi ve test was recorded when syncope or pre-syncope occurred with a rapid fall (> 30%) in blood pressure. The impact on tilt result of the type of symptoms, presence of significant structural heart disease (SHD), presence of a non-cardiovascular cause of sudden diminished consciousn ess (SDC), and age was then assessed by subgroup analysis. Patients-14 5 patients (73 female, mean age 51 (25), range 8-94) with one or more episodes of pre-syncope or syncope. Results-39 patients (27%, 21 femal e, age 49 (25) years) had positive tests and 106 (73%, 52 female, age 52 (25) years) negative tests. 27 (69%) had a positive test during bas eline tilt at 20.5 (10.8) minutes, five (13%) with isoprenaline infusi on, and seven (18%) with edrophonium bolus. Patients with recurrent sy ncope rather than single syncopal episodes or single or recurrent pre- syncope were more likely to have a positive tilt test (41% er 17%, P < 0.005) and patients with SHD or SDC (69/14 patients) were much less l ikely than patients without (16% v 42%, P < 0.0001). The yield of posi tive tests was similar if patients were below (26%) or above (27%) the mean age (50 years). When multiple factors were combined, the yield r anged from 0% for 21 patients under 50 years with SHD or SDC and witho ut recurrent syncope to 73% in 11 patients over 50 years with recurren t syncope and no SHD or SDC. The additional yield in subgroups over 45 minute baseline tilt (70 (11)%) of isoprenaline (13 (10)%) was simila r to that of edrophonium (17 (8)%, P = NS), but six (50% of those who were drug positive) patients required a second drug to produce a posit ive result (two with isoprenaline second, four with edrophonium second ). Conclusions-Head-up tilt testing in a heterogeneous population has a low yield. Simple clinical characteristics define the type of patien t who is likely to have a positive tilt test and the patient who is no t and in whom other investigations should receive priority. The great majority of positive tests will occur during prolonged baseline testin g if this is used. Isoprenaline and edrophonium produced similar addit ional yields of positive tests.