Extreme left anterior oblique projection guided leadless pacemaker implantation: a pilot study
Authors: Estevez Paniagua A , Briongos Figuero S , Sanchez Hernandez A , Munoz Aguilera R 
Published: May 2024

Abstract

Introduction
Cardiac perforation with leadless pacemakers (LPM) remains a concern. Non-septal placement seems to be the main cause, with frequent delivery in the right ventricular (RV) free wall when using standard 30-40º left anterior oblique (LAO) projections. Thus, individualized angulations might be considered, because distinguishing septal from free-wall location with standard projections has been proved to be unreliable: previous studies have shown frequent RV free wall position misclassified as septal when using 30-40º LAO.

Methods
This is a single-center, observational pilot study, comparing a 60º LAO approach LPM (VR or VDD) implant technique with the standard one. All consecutive patients who received LPM using non-standard LAO projections (study cohort) were compared with an immediately retrospective cohort of consecutive patients who received LPM using only standard projections in the same institution (control cohort). In the study group, sequential 30-40º and 60º LAO projections were performed, and a RV transvenous reference was also considered in cases with preexisting pacing leads or by placing an electrophysiological catheter into an apical-septum position upon implanter´s criterion.
The primary endpoint was the need of repositioning the delivery catheter in the study cohort, due to unproper position in the 30-40º LAO angulation. The secondary endpoints were: 1) procedural characteristics (procedure and fluoroscopy times, final fluoroscopic device position and number of deployments); 2) procedure related complications (the composite of vascular complications, implant failure, cardiac perforation, and device dislodgement); 3) acute pacing parameters.

Results
Twenty-one patients who received LPM using both 30-40º and 60º LAO (study cohort) were compared with 84 patients who received LPM using only 30-40º LAO. Delivery catheter repositioning was needed in 73,7% of patients (n=16/21) in the study cohort, most of them (n=14/16, 77,5%) due to catheter towards RV free wall, distinguished with 60º LAO from 30-40º LAO. Placement in non-midseptal locations was more common in the control group compared to the study group (74.7% vs. 42.8%, p=0.006). The median number of delivery attempts was higher in the study group (1.8±1.3 vs. 1.3±0.9, p=0.010), with longer procedural times. Threshold tended to be higher in the study group (0.8±0.7Vx0.4ms vs. 0.5±0.3Vx0.4ms, p=0.063), with smaller R-wave sensing (9.2±3.7mV vs. 11.4±4.4mV, p=0.038) and impedance (757±207ohms vs. 1026±314ohms, p&lt;0.001).

Conclusion
60º LAO frequently identified catheter mislocations using 30-40º LAO, helping to avoid RV free wall LPM deployment. This intervention resulted in longer procedures, possibly due to a higher number of repositions and delivery attempts. Pacing parameters remained adequate, although there was a trend for higher threshold, meanwhile sensing and impedance were lower, maybe related to worse myocardial contact when true septal placement is achieved.Study group implant sequenceBaseline and procedural characteristics