Importance of monitoring zones in the detection of arrhythmias in patients with implantable cardioverter-defibrillators under remote monitoring.

INTRODUCTION: Implantable cardioverter-defibrillator (ICD) monitoring zones (MZ) provide passive features that do not interfere with the functioning of active treatment zones. However, it is not known for certain whether programming an MZ affects arrhythmia detection by the ICD. The aim of the present study is to assess the clinical relevance of MZ in a population of patients with ICDs.

METHODS: In this retrospective analysis of patients with ICDs, with or without cardiac resynchronization therapy, for primary prevention under remote monitoring, the MZ was analyzed and recorded arrhythmias were assessed in detail.

RESULTS: A total of 221 patients were studied (77% men; age 64±12 years). Mean ejection fraction was 30±12%. The mean follow-up was 63±35 months. One hundred and seventy-four MZ events were documented in 139 patients (62.9%): 74 of non-sustained ventricular tachycardia (NSVT), 42 of supraventricular tachycardia, 44 of atrial fibrillation/atrial flutter, and five cases of noise. Among the 137 patients who presented with arrhythmias in the MZ (excluding two cases with noise detection only), 22 (16.1%) received appropriate shocks and/or antitachycardia pacing (ATP), while of the other 84 patients, 15.5% received appropriate ICD treatment (p=NS). In patients who presented with NSVT in the MZ, 15 (20.5%) received appropriate shocks and/or ATP. In accordance with the MZ findings, physicians decided to change outpatient medication in 41.7% of all patients in whom arrhythmic events were reported.

CONCLUSION: Ventricular and supraventricular arrhythmias are common findings in the MZ of ICD patients. Programming an MZ is valuable in the diagnosis of arrhythmias and may be a useful tool in clinical practice.