719-3 Usefulness of Signal-Averaged ECG, Head-up Tilt and Eleetrophysiologic Studies in Patients with Unexplained Syncope

The recent availability of non-invasive diagnostic methods such as signalaveraged ECG (SAECG) and Head-up tilt (HUT) have raised the need to evaluate the role of such tests for the screening of pts with recurrent unexplained syncope (US). The purpose of the present study was to identify the clinical variables that predicted an abnormal SAECG and HUT in a series of 70 consecutive pts. referred for assessment of recurrent US. SAECG (ART EPX 1200) and HUT @ 60° with a low-dose isoproterenol protocol for 30 minutes, were performed in all pts. SAECG was considered (+) if≥2 of Simson criteria were abnormal. A (+) HUT was defined as the induction of presyncope or syncope associated with bradycardia and hypotension that resembled the clinical episode. All pts underwent 2D-echo, radionuclide angiography and electrophysiologic study (EPS).VT(+)SAECG(+)SAECG(–)HUT(+)HUT(–)EPSN Pts24(34%)46(64%)30(42%)40(57%)29(41%)AGE42±1245±1636±10*55±10*45±15EF%34±8*53±655±953±536±5*PMI16(67%)*4(9%)2(6.6%)2(5%)19(66%)*EF=Eyection fraction. PMI=Previous myocardial infarction.*=Multivariabie analysis p<0.01A (+) SAECG, previous MI and EF<40% were highly predictive (95%) of induction of sustained monomorphic VT during EPS. Similarly, (–) SAECG and age<50 yrs were associated with a (+) HUT in 96%. Overall a cause for US was determined in 77%.ConclusionsA (+) SAECG, EF<40% and history of a previous MI were highly predictive of the induction of VT during EPS in pts with US. A (–) SAECG, EF>40% and age>50 yrs were predictive of a (+) HUT. Noninvasive screening of pts with US with SAECG and HUT increased the diagnostic yield and should be performed prior to invasive assessment with EPS