title: Predicting the outcome of patients with unexplained syncope undergoing prolonged monitoring.
abstract: Patients with unexplained syncope are often considered candidates for prolonged monitoring or empiric pacing when noninvasive and invasive investigations fail to provide a diagnosis. Identifying the outcome of patients undergoing prolonged monitoring that would ultimately benefit from empiric pacing may permit a cost-effective approach to resolution of syncope. Two hundred and six patients (age 57 +/- 18 years, 57% male) underwent prolonged monitoring with an implanted loop recorder for syncope of unknown origin. The median number of previous syncopal episodes was four (mean 29 +/- 133). Prior tilt testing was performed in 63% of patients, and electrophysiological testing in 46%. Symptoms recurred during follow-up in 142 patients (69%). Recurrence was associated with bradycardia leading to pacemaker implantation in 35 patients (17.0%), tachycardia in 12 (5.8%), sinus rhythm in 63 (30.6%), neurally mediated syncope based on rhythm and clinical assessment in 22 (11%), and failed activation in 10 (5%). Logistic regression analysis of baseline variables found that age was the only independent variable that predicted the need for pacing, associated with a 3% increase in risk per advancing year of age (odds ratio 1.027, P = 0.026). Despite this finding, no age group could be identified in which the likelihood of requiring pacing exceeded 30%. Logistic regression also found that patients with structural heart disease were less likely to experience recurrent symptoms during monitoring (49% vs 78%, P = 0.001) and that advancing age was associated with earlier recurrence of symptoms (P = 0.01). The etiology of recurrent syncope is diverse and cannot be predicted by baseline clinical variables. Empiric pacing appears to have little role in the management of this patient population.
authors.affiliation: Division of Cardiology, University of Western Ontario, London, Ontario, Canada. akrahn@julian.uwo.ca
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Krahn
authors.forename: George J
authors.initials: GJ
authors.lastname: Klein
authors.forename: Adam
authors.initials: A
authors.lastname: Fitzpatrick
authors.forename: Karlheinz
authors.initials: K
authors.lastname: Seidl
authors.forename: Amir
authors.initials: A
authors.lastname: Zaidi
authors.forename: Allan
authors.initials: A
authors.lastname: Skanes
authors.forename: Raymond
authors.initials: R
authors.lastname: Yee
mesh_terms: D000367:Age Factors; D000704:Analysis of Variance; D001919:Bradycardia / Q000150:complications / Q000503:physiopathology / Q000628:therapy; D002304:Cardiac Pacing, Artificial; D015716:Electrocardiography, Ambulatory; D005260:Female; D006339:Heart Rate; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012307:Risk Factors; D013575:Syncope / Q000175:diagnosis* / Q000503:physiopathology / Q000517:prevention & control; D013610:Tachycardia / Q000150:complications / Q000503:physiopathology / Q000628:therapy; D018667:Tilt-Table Test