A Self-Expanding Nitinol Fixation System for Atrial Leadless Pacemakers: Biomechanical Design and Evaluation

Q: What is the clinical evidence from this study?

Population: Atrial pacing / Left atrial appendage fixation. Intervention: Self-expanding nitinol fixation system (0.2 mm strut mesh design) with flexible polylactic acid adapter for atrial leadless pacemakers vs. 0.5 mm strut mesh fixture design and varying LAA anatomical orientations (0°, -10.5°, +10.5°). Primary outcome: Gravitational pacemaker displacement and fixture-expansion biomechanical stress/strain.

Q: What does this research mean for the field?

A 0.2 mm self-expanding nitinol fixation system enables stable anchoring for atrial leadless pacemakers in the left atrial appendage with low displacement and stress well below the permanent deformation limits of nitinol. Novelty: ClaimNovelty.METHODOLOGICAL. Consensus alignment: ConsensusAlignment.NEUTRAL.

Yu‐Tzu Wang; Yu‐Sheng Lin; Yu‐Wei Lin; Chun-Ming Chang; Lung‐Sheng Wu; Chao‐Sung Lai; Pao‐Hsien Chu

doi:10.3390/bioengineering12050512

May 12, 2025BioengineeringOpen Access

A Self-Expanding Nitinol Fixation System for Atrial Leadless Pacemakers: Biomechanical Design and Evaluation

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Key result

A novel 0.2-mm nitinol fixation system provides stable LAA leadless pacemaker anchoring with minimal displacement.

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Why the study?

Current atrial leadless pacemakers face significant challenges related to fixation stability, perforation risk, and retrievability.

Does a novel self-expanding nitinol fixation system with a 0.2 mm strut mesh provide adequate biomechanical stability and safe stress-strain tolerances for anchoring an atrial leadless pacemaker within the left atrial appendage?

Key Points

To evaluate the biomechanical feasibility, structural safety, and fixation stability of a novel self-expanding nitinol anchoring system designed for atrial leadless pacemakers deployed within the left atrial appendage.
Conducted finite-element simulations of gravitational pacemaker drop across 0° (neutral), −10.5° (orifice facing upward), and +10.5° (orifice facing downward) left atrial appendage orientations.
Simulated fixture expansion from an initial diameter of Ø8 mm to a final diameter of Ø22 mm comparing 0.2-type and 0.5-type strut mesh designs against nitinol material thresholds.
Pacemaker drop analysis demonstrated displacements of 0.21 mm at 0°, 0.058 mm at −10.5°, and 0.46 mm at +10.5° orientations, showing increased instability in downward-tilted models.
The 0.2-type fixture expanded to Ø22 mm with a von Mises stress of 504.49 MPa and strain of 0.0085 (0.85%), remaining well below the 1133 MPa ultimate tensile strength and 6% permanent deformation limit of nitinol.

Structured PICO

Does a novel self-expanding nitinol fixation system with a 0.2 mm strut mesh provide adequate biomechanical stability and safe stress-strain tolerances for anchoring an atrial leadless pacemaker within the left atrial appendage?

P

Population

Computational finite-element analysis using 3D computer-aided design models of the left atrial appendage across three anatomical orientations (0°, +10.5°, and -10.5°).

I

Intervention

Self-expanding nitinol (NiTi) umbrella-shaped fixation system (initial diameter Ø8 mm expanding to Ø22 mm, height 10.35 mm, 0.2 mm strut width) with a flexible polylactic acid (PLA) adapter (inner diameter Ø6.7 mm, wall thickness 0.3 mm) securing a leadless pacemaker model (Ø6.7 mm diameter, 25.8 mm length, 8 g weight).

C

Comparator

0.5 mm strut width nitinol fixture design (0.5 type) and comparison across three LAA anatomical orientations (0° neutral, -10.5° upward-tilted, and +10.5° downward-tilted).

O

Outcome

Gravitational pacemaker displacement (in mm) during drop analysis and biomechanical von Mises stress (MPa) and strain (%) during fixture expansion from Ø8 mm to Ø22 mm.surrogate

Main Result

Absolute Event Rate: 504.49% vs 478.85%

Finite-element modeling demonstrates the biomechanical feasibility of an umbrella-shaped, self-expanding nitinol fixation system in the left atrial appendage to securely anchor atrial leadless pacemakers and potentially serve as a dual-function LAA occluder.

Limitations

In silico finite-element simulation without in vivo preclinical or clinical validation
Simplified material assumptions in the drop analysis (fixture modeled as linear elastic rather than superelastic)
Expansion analysis geometry simplified to 1/10 of full model assuming axial symmetry
Lack of evaluation under dynamic cardiac contractility, blood flow, and long-term physiological fatigue loading
Computational finite-element analysis only, requiring future in vivo porcine model validation
Simplified material modeling in the drop analysis where nitinol was modeled as an isotropic elastic material rather than superelastic
Fixture-expansion model simplified to 1/10 geometry assuming axial symmetry and frictionless contact with the LAA
Does not account for dynamic cardiac wall motion, endothelialization, or long-term cyclic fatigue

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Implication

Supports preclinical LAA fixation feasibility in modeling; leaves open clinical translation pending in vivo validation.

Abstract

Atrial leadless pacemakers (ALPMs) offer a minimally invasive solution for patients requiring atrial pacing, but current designs face significant challenges related to fixation stability, perforation risk, and retrievability. This study presents a novel self-expanding nitinol fixation system designed for deployment within the left atrial appendage (LAA), incorporating a flexible adapter for secure pacemaker engagement and retrieval. Finite-element simulations were conducted to assess gravitational displacement across different anatomical orientations, and fixture-expansion behavior was analyzed under various mesh configurations. The pacemaker drop analysis results demonstrated minimal displacement in neutral and upward-tilted LAA models, with increased instability observed in downward-tilted orientations. The fixture-expansion study showed that the 0.2 mm mesh design provided adequate mechanical strength and strain tolerance while maintaining a compact profile. This novel fixation system improves current ALPM limitations by providing stable, retrievable anchoring and favorable biomechanical performance. It may also serve as a dual-function platform for atrial pacing and stroke prevention when integrated with a left atrial appendage (LAA) occluder. These findings support further preclinical validation for clinical translation.

Discussion

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Cite This Study

Wang et al. (2025) studied Atrial pacing / Left atrial appendage fixation. Self-expanding nitinol fixation system (0.2 mm strut mesh design) with flexible polylactic acid adapter for atrial leadless pacemakers vs. 0.5 mm strut mesh fixture design and varying LAA anatomical orientations (0°, -10.5°, +10.5°) was evaluated on Gravitational pacemaker displacement and fixture-expansion biomechanical stress/strain. The 0.2 mm self-expanding nitinol fixation system achieved stable LAA expansion with 504.49 MPa von Mises stress (0.85% strain) and minimal gravitational displacement (0.058 to 0.46 mm).

synapsesocial.com/papers/6a7c9b9810d8655be6fab2b3 https://doi.org/10.3390/bioengineering12050512

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A Self-Expanding Nitinol Fixation System for Atrial Leadless Pacemakers: Biomechanical Design and Evaluation

Figures

Key Points

Structured PICO

Main Result

Limitations

Ask about this paper

Implication

Abstract

Discussion

Cite This Study

A Self-Expanding Nitinol Fixation System for Atrial Leadless Pacemakers: Biomechanical Design and Evaluation

Figures

Key Points

Structured PICO

Main Result

Limitations

Ask about this paper

Implication

Abstract

Discussion

Cite This Study

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