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TOPLINE:

In patients newly diagnosed with cardiac amyloidosis (CA), continuous rhythm monitoring using implantable loop recorders found that clinically significant yet asymptomatic arrhythmias were common, varied by amyloid subtype, and were closely linked to the degree of myocardial infiltration and baseline conduction abnormalities.

METHODOLOGY:

• Researchers conducted a prospective observational study (EXCALIBUR) to characterize arrhythmia burden using implantable loop recorders in patients newly diagnosed with CA.
• They included 110 treatment-naive patients (mean age, 70.4 years; 80% men) between May 2021 and June 2022 at a UK specialist center. Of them, 63 had transthyretin amyloid cardiomyopathy (ATTR-CM) and 47 had light‑chain CA (AL-CA).
• All patients underwent comprehensive phenotyping, including cardiac MRI with mapping of the myocardial extracellular volume, and received subcutaneous implantable loop recorders (Reveal LINQ, Medtronic) for continuous rhythm monitoring.
• Loop recorders were set to detect bradycardia (< 50 beats/min), pauses (> 3 seconds), and tachycardia (> 110 beats/min), with daily data downloads reviewed by experts. The team documented Class I pacemaker-indicated clinically significant bradyarrhythmias, new atrial fibrillation (AF), ventricular arrhythmias, and terminal rhythms in fatal cases.
• Patients were followed up for a median duration of 36 months, with a minimum planned follow‑up period of 18 months.

TAKEAWAY:

• Clinically significant bradyarrhythmias occurred in 17.3% of patients, more often in those with ATTR-CM vs AL-CA (23.8% vs 8.5%; P = .036). Each 1-millisecond longer baseline QRS duration was associated with a 3% increased risk for these events, and each 1% increase in myocardial extracellular volume was associated with a 6% increased risk (P < .01 for both).
• New-onset AF occurred in 28.2% of patients without prior AF, more often in those with ATTR-CM vs AL-CA (50.0% vs 12.2%; P < .001). Increased myocardial extracellular volume appeared to be associated with increased risk for AF, although the CI bordered 1.00 (P = .038).
• Sustained ventricular arrhythmias occurred in 2.7% of patients and occurred exclusively in patients with AL‑CA (P = .042).
• During follow-up, 19.1% of patients died. All cases of ATTR-CM deaths and 81.8% of AL-CA deaths showed pulseless electrical activity, whereas 18.2% cases of AL-CA fatalities had sustained ventricular arrhythmias.

IN PRACTICE:

“[The study] findings highlight the importance of rhythm surveillance in cardiac amyloidosis, particularly for the detection of subclinical AF and clinically significant bradyarrhythmias, which may otherwise remain unrecognized,” the researchers of the study wrote.

SOURCE:

The study was led by Adam Ioannou, MBBS, PhD, and Rishi Patel, MBBS, both from University College London in Royal Free Campus, London, England. It was published online on May 10 in the Journal of the American College of Cardiology.

LIMITATIONS:

The study was conducted at a single specialist center, which may have introduced selection bias and limited generalizability. A modest sample size and few events, especially in the AL‑CA group, prevented reliable multivariable analyses. Researchers acknowledged the need to interpret findings cautiously because of the small number of events.

DISCLOSURES:

The study received support from an American Heart Association action grant. Several authors reported receiving consulting fees, speaker fees, and/or research support from a range of pharmaceutical, biotechnology, and medical device companies. Several authors also reported fellowship or grant support from external funding bodies.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.