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Exploration of Arrhythmia Burden in Cardiac Amyloidosis Using Implantable Loop Recorders: The EXCALIBUR Study
Adam Ioannou1, Rishi Patel1, Josephine Mansell1
1National Amyloidosis Centre, University College London, Royal Free Campus, Rowland Hill Street, London, United Kingdom.
Insights
Cardiac amyloidosis patients frequently experience significant, often asymptomatic, arrhythmias. The type and burden of arrhythmias differ between transthyretin amyloid cardiomyopathy and light-chain amyloidosis, correlating with disease severity.
Area of Science:
- Cardiology
- Electrophysiology
- Cardiomyopathy Research
Background:
- Cardiac amyloidosis (CA) is a progressive infiltrative cardiomyopathy.
- It is associated with conduction disease and arrhythmias, but their full extent and relation to disease phenotype are unclear.
Purpose of the Study:
- To prospectively characterize the arrhythmic burden in CA using implantable loop recorders (ILRs).
- To explore associations between arrhythmia patterns, amyloid subtype, and disease characteristics.
Main Methods:
- Prospective, single-centre observational study of 110 treatment-naïve patients with transthyretin amyloid cardiomyopathy (ATTR-CM) or light-chain CA (AL-CA).
- Comprehensive phenotyping including cardiac magnetic resonance, followed by ILR implantation.
Main Results:
- 17.3% of patients experienced bradyarrhythmias requiring pacemakers, more common in ATTR-CM than AL-CA.
- Baseline conduction abnormalities and higher myocardial amyloid burden predicted bradyarrhythmic events.
- New atrial fibrillation (AF) occurred in 28.2%, more frequent in ATTR-CM, with higher amyloid burden increasing risk.
- Mortality was 19.1%; terminal rhythms differed between ATTR-CM and AL-CA.
Conclusions:
- Clinically significant arrhythmias are common and often asymptomatic in CA.
- Arrhythmic burden and patterns vary by amyloid subtype and correlate with disease phenotype and amyloid load.
- Findings offer insights into CA arrhythmogenesis, supporting further research for risk stratification and management.
Background:
Cardiac amyloidosis (CA) is a progressive infiltrative cardiomyopathy associated with conduction disease and arrhythmias, although their true burden and relationship with disease phenotype remain incompletely defined.
Objectives:
The purpose of this study was to prospectively characterize arrhythmic burden using implantable loop recorders and explore associations with amyloid subtype and disease characteristics.
Methods:
In this prospective single-center observational study, 110 treatment-naïve patients with a new diagnosis of transthyretin amyloid cardiomyopathy (ATTR-CM) or light-chain cardiac amyloidosis (AL-CA) underwent comprehensive phenotyping, including cardiac magnetic resonance, followed by implantable loop recorder implantation.
Results:
Among 110 patients (ATTRwt-CM: 43, ATTRv-CM: 20, AL-CA: 47) bradyarrhythmias with a Class I indication for pacemaker implantation occurred in 17.3% and were more frequent in ATTR-CM than AL-CA (15 [23.8%] vs 4 [8.5%]; P = 0.036). Baseline conduction abnormalities (QRS duration: sHR: 1.03; [95% CI: 1.01-1.04]; P < 0.001) and higher myocardial amyloid burden were associated with subsequent bradyarrhythmic events (ECV: sHR: 1.06 [95% CI: 1.02-1.10]; P = 0.002). New atrial fibrillation occurred in 28.2% of patients without prior atrial fibrillation and was more frequent in ATTR-CM than AL-CA (15 [50.0%] vs 5 [12.2%]; P < 0.001) with higher amyloid burden associated with increased risk (ECV: sHR: 1.04; 95% CI: 1.00-1.08; P = 0.038). During follow-up 21 (19.1%) patients died (ATTR-CM: 10 [15.9%]; AL-CA: 11[23.4%]). In patients with ATTR-CM, the terminal cardiac rhythm was uniformly pulseless electrical activity; in patients with AL-CA, PEA was the terminal rhythm in 9 (81.8%) patients and 2 (18.2%) had sustained ventricular arrhythmias.
Conclusions:
In CA, clinically significant arrhythmias are common and frequently asymptomatic. Arrhythmic burden and patterns differ between amyloid subtypes and are closely associated with disease phenotype and myocardial amyloid burden. These findings provide prospective insights into arrhythmogenesis in CA and support the need for further studies to refine risk stratification and inform management strategies. (Exploration of Arrhythmia Burden in Cardiac Amyloidosis Using Implantable Loop Recorders [EXCALIBUR]; NCT04856267).
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