Caught in the Act: A Detailed Analysis of Cardiac Event Monitoring in a Cohort of Pediatric and ACHD Patients.

Background: Event monitors are being increasingly used in pediatric and adult congenital heart disease (ACHD) patients for arrhythmia evaluation. Data on their diagnostic yield are limited.

Objectives: To evaluate the diagnostic yield of event monitors, patient characteristics associated with critical events, and clinical response to events.

Methods: We retrospectively assessed event monitors prescribed to patients at our institution's Heart Center from 2017 to 2020. Thirty-day event monitor tracings were reviewed by an electrophysiologist (EP) to identify critical events defined as supraventricular tachycardia (SVT, re-entrant, atrial tachycardia, atrial flutter, and atrial fibrillation), ventricular tachycardia (VT), atrioventricular block, and pauses greater than 3 s. Patient characteristics and treatment data were collected. Characteristics associated with events were assessed using multivariable logistic regression. Trends in monitor prescription over time, diagnostic yield, and clinical response to events were analyzed.

Results: 204/2330 (8.8%) event monitors had EP-confirmed critical events. Critical events included SVT (51.5%), VT (38.5%), atrioventricular block (4%), and pauses (6%). 129/198 (65%) patients with critical events underwent treatment. Event monitoring usage increased by 52% between 2017 and 2020 (p < 0.0001). Complex CHD (OR 2.1, 95% CI 1.3-3.4, p = 0.004), cardiomyopathy (OR 2.9, 95% CI 1.5-4.8, p < 0.001), and EP-ordered monitors (OR 1.6, 95% CI 1.2-2.1, p = 0.001) were more highly associated with critical events.

Conclusion: Event monitor use is common, and critical events were captured in 8.8% of patients. The majority of patients with critical events underwent treatment. Factors associated with critical events include EPs as ordering providers, complex CHD, and cardiomyopathy.