Incidence and predictors for pacemaker implantation in transthyretin cardiac amyloidosis

Abstract

Introduction

The occurrence rate and factors influencing pacemaker (PM) implantation among patients with transthyretin cardiac amyloidosis (ATTR) have not been extensively investigated.

Objective

Our objective was to analyze the patterns of permanent PM implantation and to identify predictors for future PM placement in ATTR patients.

Method

We enrolled consecutive patients diagnosed with ATTR at referral center between 2016 and 2022. Clinical, laboratory and echocardiographic data were analysed. The primary outcome of the study was PM implantation. Patients with pre-existing PM (n = 31) at the time of ATTR diagnosis were excluded.

Results

The study population included 160 patients, 88% male, median age 82 (76.85) years. During a median follow-up of 33 months, 37 (23.1%) patients underwent PM implantation. The indications for PM implantation were: 7 patients had a third-degree atrioventricular (AV) block (18.9%), 4 patients had a second-degree type 2 AV block (10.8%); 8 patients (16.2%) had advanced conduction impairment (trifascicular block or syncope with bifascicular block); 8 patients had an indication for cardiac resynchronisation therapy (21.6%); 6 patients (16.2%) with atrial fibrillation (AF) intolerant to rate control therapy underwent atrioventricular node ablation in addition to the PM implantation and 4 patients had AF with symptomatic low heart rate (10.8%). ECG demonstrated a more prolonged PR interval (200 (180–238) vs 180 (160–204) ms, P = 0.007) and increased QRS duration (130 (100–150) vs 100 (95–120) ms, P < 0.001) with higher rate of both left and right bundle branch block (P = 0.004) in patients requiring PM implantation. The echocardiogram showed a more dilated left atrium with a higher stiffness index and an increased interventricular septum (IVS) thickness. Patients that underwent PM implantation had a worse left ventricular (LV) systolic as measured by LV ejection fraction and global longitudinal strain and a more impaired right ventricular (RV) function with a lower TAPSE and RV free wall strain than patients that were not stimulated. At multivariable analysis, IVS thickness (HR = 1.27, P = 0.001) and first-degree AV block (HR = 3.6, P = 0.006) were independently associated with PM implantation.

Conclusion

In our cohort of patients with ATTR, conduction system disease was the main indication for PM implantation. The presence of first-degree atrioventricular block and increased IVS thickness were independent factors associated with PM implantation.