Diagnostic assessment of recurrent unexplained syncope with a new subcutaneously implantable loop recorder

Aim Patients with recurrent syncope undiagnosed after extensive non-invasiv e and invasive testing pose a diagnostic and therapeutic dilemma. Holter mo nitoring is nondiagnostic in 90% of cases. Recent developments in loop reco rder technology permit long-term ECG monitoring in patients with recurrent unexplained syncope. The aim of this study was to report the worldwide expe rience with a new subcutaneously implantable loop recorder, implanted in 13 3 patients with unexplained syncope and negative laboratory investigations. Methods and Results The implantable loop recorder monitors continuously a s ingle lead electrogram using two sensing electrodes on the device shell. Th e device was implanted in 133 patients, 67 male and 66 female with recurren t syncope. During a mean follow-up of 10.8 +/- 4.3 months after device impl antation, 83 patients (62%) experienced syncope or pre-syncope. In the rema ining 50 patients no diagnosis could be made because either no events occur red, the patients were lost to follow-up, had adverse events, or died prior to diagnosis. In 72 of the 83 patients with syncope during follow-up (87%) , loop recording definitively determined whether an arrhythmia was the caus e of symptoms or not. Diagnosis included bradycardia in 21 patients, pacema ker dysfunction in one patient, and tachycardia in 10 patients. One patient experienced multiple rhythm disturbances. Syncope was non-arrhythmic in 40 patients. The remaining 11 patients failed to press the activator. Therapy was instituted in all patients, in whom an arrhythmic cause was found. Sev ere anticipated device related complications occurred in three patients. Conclusion An implantable loop recorder is useful for establishing a diagno sis when symptoms are recurrent but too infrequent for conventional monitor ing techniques. (Europace 2000; 2: 256-262) (C) 2000 The European Society o f Cardiology.