HEAD-UP TILT TEST - A NONSPECIFIC METHOD OF EVALUATING PATIENTS WITH BIFASCICULAR BLOCK

Background Patients with bifascicular block have an increased risk of syncopal attacks, but the underlying mechanism often remains unclear d espite an extensive diagnostic workup. The head-up tilt test has been established as an important diagnostic tool in the unmasking of vasova gal syncope in patients with unexplained syncope. Its role in the eval uation of patients with bifascicular block has not been studied. Metho ds and Results A head-up tilt test, using a 60 degrees angle of tilt f or 45 minutes without pharmacological provocation, was performed in 25 patients with bifascicular block and syncope that remained unexplaine d after an extensive invasive and noninvasive electrophysiological inv estigation. As a control group, 25 subjects with bifascicular block wi thout syncope, matched for age, sex, left ventricular function, and un derlying heart disease, were included. A positive head-up tilt test wa s found in 7 (28%) of the syncope patients and in 8 (32%) of the contr ol subjects (P=NS). Six patients, of whom 3 had a positive tilt test, had recurrent syncopal attacks during 32 months of follow-up. None of the control subjects had syncope during follow-up. Conclusions This st udy gives rise to serious concern regarding the specificity of the hea d-up tilt test in patients with bifascicular block. A head-up tilt tes t should therefore be interpreted with caution, and its role as a diag nostic tool in this patient category remains to be established.