Positional Nocturnal Non-Capture in Aveir VR Leadless Pacemakers

Primary Mechanisms:

1. Partial Helix Disengagement:
   • Incomplete initial helix deployment or engagement
   • Micro-dislodgement post-implantation
   • Insufficient tissue penetration depth
   • Helix engagement in trabeculated rather than solid myocardium
2. Gravitational Effects:
   • Device weight (~2 grams) exerts different vectors in various positions
   • Supine position may increase separation between helix tip and myocardium
   • Upright position may improve helix-tissue contact through gravitational settling
3. Ventricular Wall Geometry Changes:
   • Postural changes affect RV wall tension and curvature
   • Venous return changes alter RV volume and wall position
   • Supine position increases venous return, potentially displacing helix
4. Cardiac Filling Dynamics:
   • Increased preload in supine position alters RV geometry
   • Wall stress changes may affect helix-myocardium contact
   • Respiration-induced cardiac motion more pronounced when supine

Definitive Diagnosis Requires:

1. Clinical symptoms that are position-dependent (worse supine, improved upright)
2. Hemodynamic changes with position:
   • HR differential ≥20 bpm between positions
   • SpO2 improvement ≥3% with upright position
3. Device interrogation demonstrating:
   • Positional threshold variation (≥1.0V difference)
   • Loss of capture at programmed output in supine position
   • Acceptable capture in upright position
4. Exclusion of other causes of symptoms (heart failure, pulmonary disease, sleep apnea)

Step-by-Step Retrieval and Redeployment:

1. Vascular Access: Femoral vein access (18F sheath or delivery catheter)
2. Snare Capture: Use dedicated Aveir retrieval system to capture device docking button
3. Helix Retraction: Follow manufacturer protocol for helix retraction (120° counter-clockwise rotation)
4. Device Retrieval: Gentle traction to pull device into delivery catheter
   • Monitor for resistance (tissue ingrowth may prevent retrieval)
   • Use fluoroscopy to visualize device movement
5. Alternative Site Selection:
   • RV septum (preferred if original site was apex)
   • RV apex with different angulation (if original site was septum)
   • Target more trabeculated area for better helix engagement
6. Redeployment: Standard Aveir VR implantation technique
   • Confirm electrical parameters before helix deployment
   • Test thresholds in multiple patient positions BEFORE final release
   • Ensure adequate safety margin (≥2:1 voltage safety margin)
7. Post-Repositioning Testing:
   • Test capture in supine, upright, lateral positions
   • Perform gentle tug test
   • Document impedance and sensing

Best Practices to Minimize Risk of Positional Non-Capture:

1. Site Selection:
   • Prefer RV septum over apex when possible
   • Target thicker myocardium (≥10mm wall thickness on echo)
   • Avoid highly trabeculated areas where helix may not engage solid muscle
   • Consider pre-implant CT or advanced imaging for anatomy assessment
2. Helix Deployment:
   • Confirm contact with myocardium before rotation (resistance on gentle push)
   • Complete full rotation sequence (720° total rotation)
   • Visual confirmation of helix disappearance into myocardium
   • Avoid premature release during deployment
3. Positional Testing During Implant:
   • CRITICAL: Test thresholds in supine, upright, AND lateral positions BEFORE final release
   • Threshold should remain <1.0V @ 0.24ms in ALL positions
   • Any positional variation >0.5V should prompt repositioning
   • This testing adds 5-10 minutes but may prevent future complications
4. Electrical Parameters:
   • Target threshold <0.5V @ 0.24ms at implant
   • Impedance should be 400-800Ω
   • R-wave sensing >5mV
   • Document all parameters in multiple positions
5. Tug Test:
   • Gentle traction to confirm secure helix engagement
   • Device should resist moderate pull (>1lb force)
   • No movement of device on fluoroscopy during tug test

What is Positional Nocturnal Non-Capture?

For patients and families:

Your Aveir VR leadless pacemaker is a small device implanted in your heart to help maintain a normal heart rate. In rare cases, the tiny screw (called a "helix") that anchors the device to your heart muscle may not have complete contact with the heart tissue. When this happens, the device may not be able to pace your heart effectively when you lie down, but it works normally when you sit up or stand.

This condition is called "positional nocturnal non-capture" because:

• Positional: It only happens in certain body positions (usually lying down)
• Nocturnal: It typically occurs at night when you're sleeping flat
• Non-capture: The pacemaker's electrical signals aren't "capturing" or causing your heart to beat

• What caused my positional non-capture?
• Which treatment option do you recommend for me and why?
• What are the risks and benefits of each treatment option?
• How long will I need to modify my sleeping position?
• When can I expect to feel better?
• How often will I need follow-up appointments?
• What signs should I watch for that would indicate I need immediate medical attention?
• Will this affect the battery life of my pacemaker?
• Are there any activities I should avoid?
• What is the success rate of the recommended treatment?

Patient: 78-year-old male with complete heart block, Aveir VR implanted 6 weeks prior

Presentation: Reports waking up nightly with "slow heartbeat feeling" and mild dyspnea, immediately relieved by sitting up

Findings:

• Supine: HR 32 bpm, SpO2 94%, PI 16
• Upright: HR 60 bpm, SpO2 99%, PI 4
• Device interrogation: Threshold 3.2V @ 0.24ms supine, 0.6V upright

Management: Device repositioned from RV apex to mid-septum using retrieval system. New position thresholds: 0.5V supine and upright

Outcome: Complete symptom resolution, excellent function at 6-month follow-up

Patient: 82-year-old female with sinus node dysfunction, Aveir VR implanted 4 months prior

Presentation: Mild nocturnal orthopnea, prefers sleeping semi-recumbent

Findings:

• Supine: HR 28 bpm, SpO2 95%, PI 14
• Upright: HR 60 bpm, SpO2 98%, PI 3
• Device interrogation: Threshold 2.0V @ 0.24ms supine, 0.75V upright

Management: Output increased to 4.5V @ 0.5ms. Confirmed capture in all positions.

Outcome: Patient declined repositioning due to age and comorbidities. Symptom improvement with high output settings. Battery longevity estimated at 4-5 years. Close monitoring plan established.

Patient: 75-year-old male with 2:1 AV block, Aveir VR implanted 18 months prior

Presentation: Progressive worsening of nocturnal symptoms over 3 months, now unable to sleep flat

Findings:

• Supine: HR 24 bpm, SpO2 91%, PI 19
• Upright: HR 60 bpm, SpO2 97%, PI 4
• Device interrogation: Loss of capture even at maximum output (5.0V @ 1.0ms) in supine position
• X-ray: Device appears well-positioned, but extensive tissue encapsulation suspected

Management: Attempted retrieval unsuccessful due to helix encapsulation. Decision made to leave original device in place and implant traditional dual-chamber pacemaker system with RV lead positioned in septum.

Outcome: Excellent outcome with conventional system. Original Aveir device inactive but left in situ. Complete symptom resolution.

Areas Needing Further Investigation:

• Incidence and prevalence of positional non-capture in leadless pacemaker systems
• Predictors of positional complications (anatomic factors, implant technique variables)
• Optimal implantation techniques to minimize risk
• Long-term outcomes of different management strategies
• Role of advanced imaging (CT, MRI) in predicting risk
• Development of real-time positional monitoring algorithms