Implantable loop recorder for monitoring patients with congenital heart disease

Background: Patients with congenital heart defects (CHD) are prone to residua, sequels and complications from the underlying anomaly, where cardiac arrhythmias are one of the major causes for hospitalization, morbidity and mortality. The importance of the subcutaneous implantable loop recorder (ILR) for the detection and documentation of significant arrhythmias has increased over the last years. To date, however, there is little data on ILR use in the CHD population. Methods: In this single center, retrospective observational study, all CHD-patients with an ILR were identified who were under care of the German Heart Center Munich between February 2015 and January 2019. The primary endpoint of the study was the detection or exclusion of significant arrhythmias during follow-up in CHD-patients who had received an ILR. The secondary endpoint was to determine whether ILR findings influenced patient management, defined as initiation or adjustment of medication, cardioversion, electrophysiologic study, catheter ablation, or implantation of cardiac implantable electronic devices (CIEDs) such as pacemakers (PM) or implantable cardioverter-defibrillators. Results: An ILR was implanted in 33 CHD-patients (mean age, 43±20 years; 42.4% female) with CHD. During a mean observation period of 697±433 days, clinically relevant arrhythmias, correlating with the patients’ complaints and symptoms, were detected in 19 patients (59.4%), encompassing supraventricular tachycardia (n=10), supraventricular or ventricular ectopic beats (n=10), non-sustained ventricular tachycardia (n=2), ventricular tachycardia (n=2), and bradycardia (n=2). In 9 patients (28.1%) the detected arrhythmia was considered an event requiring treatment. Treatment modalities included catheter ablation (n=5), modification of antiarrhythmic drug regime (n=2), adaptation of anticoagulation therapy (n=2), or implantation of a subcutaneous ICD (n=1). Regarding the occurrence of cardiac arrhythmias or a related need for therapeutic intervention, no significant differences were identified with respect to WHO functional class, the presence of pulmonary arterial hypertension or reduced resting peripheral oxygen saturation. Conclusions: In symptomatic CHD-patients at risk for life-threatening cardiac events, ILR has a considerable complementary diagnostic value for the detection and differentiation of benign and malignant arrhythmias. Considering the overall low risk of complications, ILR implantation should be considered in patients with CHD of any complexity who need medium or long-term arrhythmia monitoring, especially if short-term Holter monitoring cannot provide sufficient diagnostic certainty.