Tilt#TableTesting in Syncopal Patients with Sick Sinus Syndrome: A Guide to Pathophysiology and Management ? Kostas A. Gatzoulis M.D., Ioannis I. Mamarelis M.D., Artemis M. Theopistou M.D., Skevos K. Sideris M.D., Katerina Avgeropoulou M.D., John H. Gialafos M.D., and Pavlos K. Toutouzas, M.D. From the University and State Cardiac Departments, Hippokration General Hospital, Athens, Greece Background: A possible role of a neurally mediated component in the syncope mechanism of patients with sick sinus syndrome has not been adequately evaluated. Methods: We examined and compared three groups: group 1, 25 syncopal patients (age 55 215, M/F 18/7, syncope attacks per patient 6 2 7) with sick sinus syndrome (persistent unexplained bradycardia with a long sinus pause and/or a long sinus node recovery time, a long sinoatrial conduction time, a low intrinsic heart rate, and/or an incompetent chronotropic response to atropine); group 2: 45 patients (age 43 218, M/F 28/17, syncope attacks per patient 6 2 7) with syncope of unknown etiology; group 3: 20 healthy controls (age 34 2 9, M/F 1614). The tilt-table test protocol used consisted of an initial 20-minute period at 80" tilt followed by three 10-minute periods in the same position under graded isoproterenol intravenous infusion at 1-3 pg/min. The test was considered positive if presyncope or syncope due to hypotension and/or bradycardia was induced. Results: A similar proportion of group 1 and group 2 patients developed a positive test (12 or 48% and 25 or 56%, respectively, P:NS) with a similar positive tilt-table test duration in both groups (41 2 22 vs 43 2 17 minutes, P:NS). In contrast, only four of the group 3 healthy controls (20%) developed a positive test with a much longer test duration (P < 0.005). Conclusions: Syncopal patients with sick sinus syndrome commonly exhibit a neurally mediated syncope reaction during a tilt-table test. This might explain the occasional failure to prevent recurrent syncope in sick sinus syndrome patients treated with cardiac pacing. Concurrent P-blocker therapy may be indicated for such patients. A.N.E. 1999;4(2):115-120 tilt-table test; sick sinus syndrome; syncope The mechanism of syncope in patients with sinus node dysfunction is usually attributed to long sinus pauses without an effective escape rhythm, result- ing in sudden loss of forward blood flow and severe cerebral hypoperfusion. Cardiac pacing is effective in reducing the incidence of syncope attacks in such patients.1 However, this therapeutic modality does not always eliminate recurrent episodes of cerebral ischemia in these patients.zJ It has been shown that patients with sinus node dysfunction have a high incidence of abnormal neurally medi- ated cardioinhibitory and vasodepressor reactions during tilting as well as hypersensitive carotid si- nus responses during carotid sinus massage.4 In a preliminary report of 12 syncopal patients with the sick sinus syndrome, we also recently found a high incidence of syncope induced during tilting.5 Thus, the possibility of the presyncope or syn- cope attacks to be provoked by other mechanisms in patients with the sick sinus syndrome cannot be Address for reprints: Kostas A. Gatzoulis, M.D., 34 Fragogianni Str., GR-156 69 Papagos, Athens, Greece. Fax: 30-01-3644570. 115