Leadless Pacemaker Placement in the Right Ventricle
Leadless pacemakers should be implanted in the right ventricular mid-septum rather than the apex, as this location reduces the risk of cardiac perforation while maintaining excellent electrical performance. 1, 2
Optimal Implantation Site
The mid-septal location is the preferred target for leadless pacemaker deployment, with studies demonstrating successful mid-septal placement in 90-94% of cases when proper fluoroscopic guidance is used. 1, 2 This represents a significant departure from traditional transvenous lead placement, where the right ventricular apex has historically been the most common site. 3
Why Mid-Septum Over Apex
The primary advantage of mid-septal placement is substantially lower perforation risk, which is the major complication associated with apical leadless pacemaker implantation. 1 In high-risk cohorts—including patients over 80 years old, those with BMI <20 kg/m², renal dysfunction, and valvular heart disease—mid-septal implantation achieved a complication rate of only 2% for perforation. 1
Specific Anatomic Targets
For leadless pacemakers, the acceptable implantation zones within the right ventricle include:
- Mid-septum (preferred): 90% of successful cases 1
- Low-septum/apical septum: 10% of cases 1
- Mid-to-apical right ventricular septum: Primary location in dual-chamber systems 4
The traditional right ventricular apex, while still used for conventional transvenous leads 5, 3, carries higher perforation risk for leadless devices due to the thinner myocardial wall at this location. 1
Fluoroscopic Guidance Technique
Three fluoroscopic views are essential for accurate mid-septal placement: right anterior oblique (RAO), left anterior oblique (LAO), and left lateral views. 1 The left lateral view is particularly critical, as 17.6% of devices that appeared septal on RAO and LAO views were actually directed toward the free wall when verified laterally. 1
Positioning Criteria by View
- RAO view: Device positioned at the center of the cardiac silhouette 1
- LAO view: Device directed toward the left 1
- Left lateral view: Device positioned away from the sternum (anteriorly) 1
Right ventriculography significantly improves accuracy, increasing correct mid-septal placement from 48% to 94% while simultaneously reducing X-ray exposure time (7.79 vs. 12.03 minutes) and radiation dose (565 vs. 826 mGy). 2 This technique illustrates the RV septum directly and reduces the number of repositioning attempts from 6.4 to 2.8. 2
Electrical Performance
Mid-septal leadless pacemaker placement demonstrates excellent chronic electrical characteristics:
- Pacing thresholds: Improve from 0.8±0.6V at implant to 0.6±0.4V at 1 month, then remain stable through 6 months 4
- R-wave sensing: Mean 9.7±4.0 mV at implantation, improving to 11.7±4.2 mV at 1 month 1, 4
- Impedance: Stable throughout follow-up 1, 4
Importantly, electrical metrics do not differ significantly among various septal implant locations (mid vs. apical septum), indicating that any septal position provides reliable performance. 4
Common Pitfalls to Avoid
Never rely solely on RAO and LAO views—the left lateral view is mandatory to exclude free wall positioning that mimics septal location on standard oblique projections. 1 One perforation in the reported series occurred specifically because contrast was injected against the RV anterior wall before lateral view verification. 1
Avoid the coronary sinus, which can be mistaken for the right ventricle; leads in the coronary sinus direct posteriorly on lateral view, while true RV leads project anteriorly. 5
Clinical Context
Leadless pacemakers are indicated for single-chamber ventricular pacing only (VVI mode), appropriate for patients with permanent atrial fibrillation, symptomatic bradyarrhythmias where atrial contribution is not needed, or following AV junction ablation. 3, 6 These devices eliminate lead-related complications (fracture, extraction challenges) and pocket complications (infection, disfigurement) that affect 2.2-4.3% of conventional transvenous leads. 5, 6
For dual-chamber leadless systems, the ventricular component is similarly placed at the mid-to-apical RV septum, with the atrial component in the right atrial appendage anterior base. 4