Abstract

Objective To stratify mechanisms and predictors of unexplained syncope documented by an implantable loop recorder (ILR) in patients with and without structural heart disease (SHD).

Design and setting Prospective study in consecutive patients of a university cardiac centre.

Patients and methods An ILR was implanted in 70 patients in whom syncope remained unexplained after thorough testing (34 male / 36 female, aged 55 ± 17 years). SHD was pre-sent in 33 patients (ischemic cardiomyopathy=16, dilated cardiomyopathy=9 and hypertrophic cardiomyopathy=8) and absent in 37 patients (LV-ejection fraction 46 ± 4% vs. 61 ± 7 %).

Results A syncopal recurrence occurred during 16 ± 8 months in 30 patients (91%) with SHD and in 30 patients (81%) without SHD. Fifteen patients (46%) versus 19 patients (51%) had an ILR-documented arrhythmia at the time of recurrence which led to specific therapy. The remaining 15 patients (46%) with SHD and 11 patients (30%) without SHD had normal sinus rhythm at the time of the recurrence. On stepwise multivariate analysis only major de-pressive disorder was predictive for early recurrence during ILR follow-up (P=0.01, HR 3.35, 95% CI). Fifty-seven percent of major depressive patients had sinus rhythm during re-currence compared with 31% of patients without (p=0.01). Conversely, no patient with major depresssive disorder had asystole compared with 33% without (p<0.0001).

Conclusions The presence of SHD has little predictive value for the occurrence or type of arrhythmia in patients with unexplained syncope. Major depressive patients are prone to early recurrence of symptoms and have no evidence of arrhythmia in most cases. The ILR leads to specific therapy in half of all patients.