Atrial Leadless Pacemaker Implantation at the Superior Right Atrial Site

Right atrial appendage (RAA) pacing may produce nonphysiological atrial activation. To evaluate the feasibility, safety, and electrocardiographic characteristics of atrial leadless pacemaker implantation at the superior right atrium (RA). Sixty-eight consecutive patients undergoing dual-chamber leadless pacemaker implantation were studied. Procedural, device, electrocardiographic, and clinical outcomes were compared between superior RA and RAA base pacing. Superior RA implantation succeeded in 26/46 attempts (56.5%), increasing from 27.8% to 60.0% and 92.3% across sequential periods. In noncrossover cases, procedure (72.7±16.4 vs 76.8±27.2 minutes; P=0.533) and fluoroscopy times (15.4±5.8 vs 18.6±11.9 minutes; P=0.249) were comparable. P-wave duration remained unchanged with superior RA pacing (99.7±29.9 to 98.1±25.6 ms; P=0.543) but increased with RAA pacing (106.7±23.1 to 134.9±25.6 ms; P<0.001); P-wave terminal force in V1 changed from 3.6% to 3.6% versus 10.0% to 45.0%, respectively (P<0.001 for RAA). PR intervals increased from 228.4±72.8 to 229.7±77.5 ms (P=0.038) and from 205.5±72.0 to 234.4±72.6 ms (P<0.001), respectively; the increase was smaller with superior RA pacing (+5.7±11.7 vs +38.6±31.3 ms; P<0.001). At 3 months, sensing amplitudes (3.4±1.5 vs 2.4±1.1 mV; P=0.091) and pacing thresholds (0.8±0.5 vs 0.8±0.3 V; P=0.785) were comparable. No pericardial tamponade occurred. During 10.4±4.6 months, mortality, heart failure events, and atrial fibrillation incidence did not differ significantly. Superior RA pacing was feasible, showed a marked learning curve, and better preserved intrinsic atrial activation than RAA pacing.