Cardiac Implantable Electronic Devices: A Window Into the Evolution of Conduction Disease in Cardiac Amyloidosis

Abstract

Objectives: This study characterized the relationship between conduction disease and cardiac amyloidosis (CA) through longitudinal analysis of cardiac implantable electronic device (CIED) data.

Background: Bradyarrhythmias and tachyarrhythmias are commonly reported in CA and may precede a CA diagnosis, although the natural history of conduction disease in CA is not well-described.

Methods: Patients with CA (transthyretin amyloidosis cardiomyopathy [ATTR-CM] and light-chain amyloidosis [AL-CA]) and a CIED were identified within the Duke University Health System. Patient characteristics at the time of implantation, including demographics and data relevant to CA diagnosis, cardiac imaging, and CIED were recorded. CIED interrogations were analyzed for pacing and atrial fibrillation (AF) burden, activity level, lead parameters, and ventricular arrhythmia incidence and/or therapy.

Results: Thirty-four patients with CA (7 with AL-CA, 27 with ATTR-CM [78% with wild-type]; 82% men) with median age of 75 years and a mean ejection fraction of 42 ± 13% had a CIED implanted for bradycardia (65%) or prevention of sudden cardiac death (35%). CIED implantation preceded CA diagnosis in 14 patients (41%). Over a mean follow-up of 3.1 ± 4.0 years, right ventricular sensing amplitudes decreased but did not result in device malfunction; lead impedances and capture thresholds remained stable. Between post-implantation years 1 and 5, mean ventricular pacing increased from 56 ± 9% to 96 ± 1% (p = 0.003) and AF burden increased from 2 ± 1.3 to 17 ± 3 h/day (p = 0.0002). Ventricular arrhythmias were common (mean episodes per patient per year: 6.7 ± 2.3 [ATTR-CM] and 5.1 ± 3.2 [AL-CA]) but predominately nonsustained; only 1 patient with AL-CA required implantable cardioverter-defibrillator therapy.

Conclusions: Longitudinal analysis of CIED data in patients with CA revealed progressive conduction disease, with high AF burden and eventual dependence on ventricular pacing, although lead parameters remained stable. Ventricular arrhythmias were common but predominantly nonsustained, particularly in ATTR-CM.

Keywords: atrial fibrillation; cardiac amyloidosis; conduction disease; defibrillator.