Abstract 4138981: Indication and electrical performance of conventional, resynchronisation and conduction system pacing in Transthyretin Amyloid Cardiomyopathy (ATTR-CM)

Background: Conduction system disease, atrial and ventricular arrhythmias may require pacemaker or ICD implantation in transthyretin amyloid cardiomyopathy (ATTR-CM). The optimal pacing mode in ATTR-CM patients remains unknown. Objective: To assess how availability of cardiac resynchronization and conduction system pacing influenced pacemaker indications and to compare early electrical performance of conventional, resynchronisation and conduction system pacing in ATTR-CM. Methods and Results: 67 of 250 (26.8%) patients presenting with ATTR-CM between June 2019 and February 2023 received a pacemaker [HA1] and were included in this retrospective analysis. Pacemaker implantation occurred in 25 patients (37.3%) prior to, and in 42 (62.7%) after ATTR-CM diagnosis. Implantation of conventional single- (VVI) or dual-chamber (DDD) pacemakers was more common (n=17/25, 68%) in undiagnosed ATTR-CM, while physiological pacing systems (CRT/ CSP) were preferably implanted in patients (n=24/42; 57.1%) after diagnosis. Sick sinus syndrome (11/35; 31.4% vs. 6/32; 18.8%) and higher degree AV-block (20/35; 57.1% vs. 9/32; 28.1%) were more common indications for VVI/DDD compared to CRT/CSP pacemakers, with pursuit of a pace/ablate strategy (12/32; 37.5%) and heart failure (5/32; 15.6%) contributing significantly to implantation of CRT/CSP. QRS width was significantly lower with CSP [122ms (IQR: 120-139)], compared to CRT [155ms (IQR: 141-160); p=0.005] or VVI/DDD [160ms (IQR: 144-180)], with the latter resulting in a significant increase in QRS width compared to intrinsic QRS [from 138 (IQR: 123-150) (p<0.001)]. LV/LBBAP pacing capture thresholds (0.4ms pulse width) were significantly lower after CSP [0.75V (IQR: 0.5-1.2)] compared to CRT [1.3V (IQR: 1.0-1.6); p=0.049]. RA and RV lead performance were comparable between all pacing systems (p>0.05). Conclusions: Pacing indications are changing with earlier diagnosis of ATTR-CM. CSP may offer improved electrical performance and resynchronization, the effect of conduction system pacing on clinical outcomes should be further explored.