Routine ambulatory heart rhythm monitoring for detection of atrial arrhythmias in transthyretin cardiac amyloidosis

Background: Atrial fibrillation and flutter (AF/AFL) are common in transthyretin cardiac amyloidosis (ATTR-CM) which in turn is associated with higher risk of thromboembolism. Detecting AF/AFL may be especially important, but the role of routine ambulatory monitoring in ATTR-CM patients is unclear. Objective: The objective is therefore to determine prevalence and outcomes of subclinical AF/AFL on routine ambulatory rhythm monitoring. Methods: We report outcomes of an observational study of patients at our Amyloidosis Center with wild-type or variant ATTR-CM diagnosed between 2005 and 2019. Patients without known AF/AFL at baseline had ambulatory ECG monitoring (duration 2-30 days) every 6 months while those with cardiovascular implantable electronic devices (CIEDs) had device interrogations instead. Results: Eighty-four patients with ATTR-CM (mean age 73.5 +/- 9.7 years, 94% male) had mean follow-up 2.3 +/- 1.9 years. Forty patients (48%) had AF/AFL before ATTR-CM diagnosis. In the remainder, 21 (48%) were subsequently diagnosed with AF/AFL: 10 (48%) based on symptoms, and 11 (52%) by monitoring. Anticoagulation (AC) was started in 9/11 (82%) patients with incidental AF/AFL. Among the entire cohort, stroke occurred in 9 patients (11%): 1 hemorrhagic and 8 ischemic (7 in patients with AF/AFL). No strokes occurred in patients on AC. Conclusion: Almost half of patients in our cohort had AF/AFL diagnosed prior to their ATTR-CM diagnosis. In the remainder, approximately half of AF/AFL diagnoses were established incidentally by routine monitoring, most of whom were promptly anticoagulated. Incidence of stroke was high overall, but no strokes occurred in anticoagulated patients. Optimal frequency and duration of monitoring needs further investigation.