IMPLANTABLE LOOP RECORDERS

 IMPLANTABLE LOOP RECORDERS When a diagnosis cannot be made with an external loop recorder because the symp- toms of palpitation, near syncope, or syncope are too infrequent, or because the pa- tient cannot tolerate wearing the monitor, a new device, which is implantable in the subcutaneous tissue, is now available. The implantable loop recorder is a small device, about the size of a flattened ballpoint pen cap, that is implanted subcutaneously in the left precordial area, just left of the sternum in the fourth to fifth intercostal space. The procedure is done as an outpatient, takes 15 to 30 minutes, and carries an extremely low risk burden. The device is a self-contained system that has 2 electrodes 2 inches apart to detect electrical activity continuously. The non rechargeable battery has a life expectancy of about 3 years on average and can provide continuous monitoring for even longer than that. The patient is provided with a monitoring box that sends information via the Internet to a centralized station. The patient's device clinic then downloads the information from the Internet at scheduled dates, typically once a month. In addition, any event that is recorded as abnormal by the device, based on programmed parameters, is transmitted automatically to the clinic as an alert. Further, when the patients are symptomatic, they can activate the recorder and transmit to the clinic. In that way, symptoms can be correlated with the rhythm to rule out or rule in a tachyarrhythmia or bradyarrhythmia. There had been no data for the usefulness of an implantable loop recorder in the diagnosis of palpitation of unknown cause, until the recent publication by Giada and colleagues 12 of the Recurrent Unexplained Palpitations (RUP) Study. These investigators compared the diagnostic yield and cost of an implantable loop recorder with a conventional strategy in patients with unexplained palpitation. After an initial evaluation by history, physical examination, and ECG, 50 patients were randomized in a multicenter prospective study to a conventional diagnostic strategy versus an implantable loop recorder. 

paroxysmal atrioventricular block. With regard to cost, the mean cost per patient was higher in the implantable loop recorder group compared with the conventional strategy group. However, the mean cost per diagnosis was significantly lower in the implantable loop recorder group. Overall, it was more cost effective to implant a loop recorder, which was much more likely to obtain a firm diagnosis in patients with unexplained palpitation (Table 3). In follow-up, patients who were diagnosed with an arrhythmia as the etiology of the palpitation had either elimination or reduction of symptoms after ablation, antiarrhythmic medications, or pacemaker implantation. Patients with a non-arrhythmic etiology of palpitation were treated with anxiolytic medications. Overall, patients with infrequent symptoms of palpitation and no significant structural heart disease were more likely to have a diagnosis with an implantable loop recorder rather than conventional strategy. Implantable loop recorders have also been shown to be beneficial in patients with unexplained recurrent syncope, when the episodes are fairly far apart.