The utility of implantable loop recorders for diagnosing unexplained syncope in 100 consecutive patients: five-year,...

The purpose of this study was to retrospectively review the 5-year experience of a university hospital with implantable loop recorders (ILR) for the diagnosis of recurrent, unexplained syncope or presyncope.

One hundred patients with syncope or presyncope of unknown etiology (negative tilt-table test, electrophysiology study and neurologic workup) underwent prolonged monitoring with an ILR from March 2000 to December 2004. All implants were performed using a first-generation (manual activation) or second-generation (manual plus automatic activation) ILR.

One hundred patients (70 women, 30 men) with a mean age of 68 +/- 18 years received the ILR. Twenty-three patients had coronary artery disease; 2 patients had dilated cardiomyopathy. Ten patients received a first-generation ILR, and 90 patients received a second-generation ILR. After 9 +/- 8 months' follow up, ILR interrogation identified an arrhythmogenic etiology to the syncope/presyncope in 45 patients with 55 events. Eight patients had a diagnosis by ILR less than 2 months from the date of implantation. Twenty-six patients had documented symptomatic bradycardia (asystole, sinus pauses, atrial fibrillation with long pauses); 11 patients had episodes of sinus tachycardia with heart rates of 130 to 140 beats/minute; 2 patients had atrial tachycardia; 5 patients had multiple episodes of nonsustained ventricular tachycardia (NSVT); 1 patient had sustained ventricular tachycardia, and 4 patients had paroxysmal supraventricular tachycardia. All arrhythmias were treated successfully by pacemaker/ICD implantation, radiofrequency catheter ablation and/or medications. One patient had seizure activity, which was detected by ILR as high-frequency noise. Two patients failed to activate their device, as it was a first-generation device.

Five-year experience with the ILR in 100 consecutive patients confirms the utility of this device in the diagnosis of recurrent, infrequent, unexplained syncope or presyncope. It helped diagnose 45% of patients with unexplained syncope with negative electrophysiologic and neurologic workup. Most of these patients had an arrhythmogenic etiology to their syncope. Medical therapy, device therapy, and/or catheter ablation helped successfully treat all patients with an arrhythmogenic etiology detected by ILR.