Predictive value of presyncope in patients monitored for assessment of syncope

Background The purpose of this study was to assess the diagnostic value of recording the cardiac rhythm during presyncope in patients undergoing monit oring for undiagnosed syncope. Methods and Results Eighty-Five patients (age, 59 +/- 18 years; 44 men, 41 women) with recurrent unexplained syncope underwent prolonged monitoring wi th an implantable loop recorder. Patients were examined for syncope, which was either recurrent or associated with at least 2 presyncopal episodes. Pa tients had a mean of 5.1 +/- 5.5 syncopal episodes in the previous 12 month s, and 70% of patients had symptoms for >2 years. Sixty-two (73%) patients had recurrent symptoms during a 12-month follow-up period. Of 150 recurrent events captured by the implantable loop recorder, there were 38 (25%) epis odes of syncope and 112 (75%) episodes of presyncope. Syncope alone recurre d in 12 patients, presyncope in 25, and both in 16. An arrhythmia was prese nt in 64% of syncopal events (bradycardia in 16, tachycardia in 2) versus 2 5% for presyncopal events (bradycardia in 7, tachycardia in 3, P = .001). A n arrhythmia was detected in 9 (56%) of the 16 patients with both syncope a nd presyncope, which was present in all recorded episodes of syncope compar ed with 6 of 9 presyncopal episodes. Patient-related failure to freeze the device after symptoms occurred in 21 (36%) of 59 syncopal events compared w ith 15 (12%) of 127 presyncopal events (P = .0001). Conclusions Syncope is more likely to be associated with an arrhythmia than is presyncope in patients undergoing extended monitoring. Presyncope is a nonspecific end point that is frequently associated with sinus rhythm. Pati ents undergoing extended monitoring for syncope should continue to be monit ored after an episode of presyncope unless an arrhythmia is detected.