A Novel Risk Score for Predicting the Difficulty in Leadless Pacemaker Implantation

MICRA, a leadless pacemaker system, is an established modality for cardiac pacing. However, its implantation can sometimes be technically challenging. This study aimed to identify anatomical factors associated with procedural difficulty during MICRA implantation, with a particular focus on preoperative CT imaging.

We retrospectively analyzed all MICRA implantations performed at our institution from 2018 to 2024. Patients were classified into two groups based on procedural difficulty, defined as a MICRA delivery system in/out time ≥ 30 min and/or three or more MICRA deployment attempts. Logistic regression was used to identify independent predictors of procedural difficulty, which were incorporated into a scoring system.

Of 122 patients, 111 with available preoperative CT imaging were included (mean age 83 years, 43% female). Procedural difficulty was observed in 37 patients (33%). Independent predictors included right atrial enlargement > 45 mm, right ventricular septal angle > 55° or < 45°, inferior vena cava (IVC)-to-tricuspid valve (TV) angle < 128°, posterior offset from the IVC ostium to the TV < 35 mm (all p < 0.05). A "Difficulty Score" was developed by assigning 1 point for each of the predictors. The score demonstrated excellent discrimination (area under the curve = 0.87).

Specific anatomical features on preoperative CT are associated with MICRA implantation difficulty. The proposed Difficulty Score may aid in risk stratification and procedural planning.