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Shock Wave Lithotripsy in patient with pacemaker

Evidence-Based Clinical Resource for Physicians

Shock Wave Lithotripsy (SWL) in patients with pace maker

Evidence-Based Clinical Resource for Physicians

ESWL in Patients with Pacemaker- Lithotripsy Academy

ESWL in Patients with Pacemaker

Evidence-based approach to extracorporeal shock wave lithotripsy in cardiac risk patients

1. Introduction to ESWL

Extracorporeal Shock Wave Lithotripsy (ESWL) is a non-invasive procedure used to fragment urinary stones using focused shock waves generated electromagnetically, piezoelectrically, or electrohydraulically. Accurate targeting with imaging ensures effective fragmentation and limits tissue damage.

2. Cardiac Arrhythmias and Pacemaker Devices: Background

2.1 Types of Pacemakers and Related Devices

Single Chamber Pacemaker: Contains one lead in the right atrium or ventricle, most commonly operates in VVI mode; less interference risk during ESWL.
Dual Chamber Pacemaker: Two leads in right atrium and ventricle, operating in DDD mode to preserve AV synchrony; more sensitive to interference.
Rate-Responsive Pacemaker: Adjusts pacing rate according to sensed physical activity; sensors can be falsely triggered by shock waves.
Biventricular Pacemaker (CRT) and ICDs: More complex devices used in heart failure and arrhythmia management requiring special peri-procedural handling.

2.2 Pacemaker Operation Modes

VVI: Ventricular pacing and sensing mode, inhibiting pacing with intrinsic beat sensing.
VOO: Asynchronous ventricular pacing, paces regardless of sensing to avoid inhibition.
DDD: Dual chamber pacing and sensing, vulnerable to shock wave interference.

3. Risks and Considerations During ESWL

ESWL shock waves can cause electromagnetic and mechanical interference affecting device sensing/pacing, leading to oversensing, undersensing, inappropriate inhibition, or triggering.
Dual chamber devices, particularly atrial sensing, are mostly affected.
Without ECG gating, ESWL may induce cardiac arrhythmias.
Proper precautions mitigate risks.

2. Technique

Pre-Treatment Optimization

Patient Positioning

**Supine position:** Standard for most renal and upper ureteral stones
**Prone position:** May improve focal point targeting in very obese patients
**Lateral decubitus:** Alternative for difficult-to-target stones
**Abdominal compression:** May reduce SSD by 1-2 cm in select cases

Imaging Modality Selection

Fluoroscopy:

May be limited by adipose tissue interference
Requires higher radiation doses in obese patients
Consider biplane fluoroscopy for improved targeting

Ultrasound guidance:

Preferred in obese patients when stone is visible
No radiation exposure
May be challenging with SSD >8-10 cm
Real-time monitoring of stone position

Equipment Considerations

Lithotripter Selection

Third-generation electromagnetic lithotripters may show improved outcomes in obese patients compared to older electrohydraulic systems, though evidence is mixed. Second-generation devices with wider focal zones may offer better penetration depth.

Technical Modifications

**Extended shock pathway:** Essential for patients exceeding standard table limits
**Increased coupling:** Ensure adequate gel application and skin contact
**Higher energy settings:** May be required but balanced against complication risk
**Longer treatment duration:** Allow additional time for positioning and targeting

Treatment Protocol

Energy Delivery Strategy

Recommended Protocol for Obese Patients:

**Ramping phase:** Start 14-16 kV, ramp to 18-20 kV over 250-500 shocks
**Treatment phase:** Deliver 2000-2500 shocks at maximum tolerated energy
**Shock wave rate:** 60-90 shocks/min (slower rate preferred for tissue protection)
**Re-targeting:** Verify focal point every 500 shocks due to patient movement

Session Parameters

**Total shocks per session:** 2000-3000 (adjust based on stone fragmentation)
**Maximum voltage:** Device-dependent, typically 18-24 kV
**Treatment intervals:** 7-14 days between sessions
**Maximum sessions:** 3 sessions before considering alternative treatment

Anesthesia and Analgesia

Obese patients may require modified anesthetic approaches:

**Intravenous sedation:** Most common; requires careful titration
**General anesthesia:** May be necessary for morbidly obese patients with airway concerns
**Analgesic supplementation:** Weight-based dosing with close monitoring
**Positioning assistance:** Additional staff may be needed for safe patient handling

Intraoperative Monitoring

Enhanced monitoring for obese patients:

Continuous pulse oximetry and capnography
Blood pressure monitoring (appropriate cuff size essential)
ECG monitoring (obesity-related cardiac comorbidities)
Respiratory monitoring (risk of hypoventilation)

Technical Challenges and Solutions

Challenge	Solution
Poor stone visualization	Switch to ultrasound guidance; use contrast imaging if available
Excessive SSD	Abdominal compression, alternative positioning, higher energy levels
Patient movement	Adequate analgesia, frequent re-targeting, shorter treatment sessions
Respiratory interference	Breath-holding technique, respiratory gating if available
Limited table capacity	Extended shock pathway, reinforced table, bariatric equipment

6. ESWL Procedural Modifications

Position the patient and lithotripter to keep the pacemaker or ICD at least 5 cm away from the shock wave path.
Use ECG gating to time shock waves during the cardiac refractory period (R wave) to reduce arrhythmia risk.
Apply lowest effective shock energy and reduce shock frequency where possible.
Continuous ECG and cardiac monitoring are mandatory with resuscitation equipment immediately available.
Limit the total number of shocks balancing treatment efficacy and safety.

Energy, Frequency & Ramping Protocols in ESWL

Optimizing the shock wave energy, frequency, and ramping protocol during ESWL is crucial for effective stone fragmentation while minimizing tissue injury and device interference risks.

Energy Level: Treatment typically starts at low energy to allow tissue adaptation and reduces patient discomfort, then gradually increased to higher energy sufficient for stone fragmentation.
Frequency: Shock wave frequency is often set between 60 to 120 shocks per minute. Lower frequencies (around 60-70/min) may improve fragmentation efficiency and reduce tissue damage.
Energy Ramping: A gradual stepwise increase ("ramping") in shock wave energy is commonly practiced in multiple phases:
- Phase 1: Initial low-energy shocks (e.g., 10-20% maximal energy) to "prime" tissue and avoid abrupt stimulation.
- Phase 2: Intermediate energy levels for continued fragmentation.
- Phase 3: Maximum energy doses to complete stone disintegration.
Clinical Evidence: Studies support that energy ramping protocols enhance stone fragmentation, decrease complications, and reduce interference with implanted cardiac devices during ESWL.
Monitoring: Close monitoring of patient response and cardiac device function during energy escalation is critical.

7. Post-Procedure Device Management and Follow-up

Immediately restore pacemaker/ICD to baseline settings post-ESWL.
Repeat device interrogation to confirm no changes in function or sensing thresholds.
Monitor for arrhythmias or device-related symptoms in the hours following the procedure.
Maintain communication with cardiology team for follow-up and documentation.

5. Review of Scientific Evidence

Clinical studies confirm ESWL safety with proper pacemaker management without reported device damage or patient harm.
Urological and cardiac societies recommend specific pre-ESWL device interrogations, reprogramming, and ECG gating to ensure safe treatment.
Case reports show successful ESWL in pacemaker-dependent patients following these protocols without complications.
Multidisciplinary care involving cardiology is emphasized.

9. Summary of Clinical Recommendations

Aspect	Recommendation
Pre-Procedure	Identify device type, baseline interrogation, cardiology consult
Pacemaker Reprogramming	Dual chamber → VVI, rate response off, ICD tachy off
ESWL Technique	Device >5 cm from shock path, ECG gating for shock delivery
Monitoring	Continuous ECG, resuscitation ready
Post-Procedure	Restore device settings, interrogate, monitor patient

10. References

Boston Scientific Corporation. Lithotripsy and Implantable Pacemaker and Defibrillator Systems. Boston Scientific, 29 Oct. 2008. PDF
Association Française d'Urologie. "2022 Recommendations of the AFU Lithiasis Committee: Extracorporeal Shock Wave Lithotripsy (ESWL)." Urofrance, 2 Nov. 2023. Website
Ubee, Samuel S., et al. "Implications of Pacemakers and Implantable Cardioverter Defibrillators on Extracorporeal Shock Wave Lithotripsy." The Journal of Urology, vol. 186, no. 4, 19 Oct. 2011, pp. 1468-1475. Article PDF
Asroff, Steven W., and Theodore E. Kingston. "Extracorporeal Shock Wave Lithotripsy in Patient with Pacemaker." The Journal of Endourology, vol. 7, no. 3, Dec. 1993, pp. 189-192. PubMed
Paterson, Robin F., et al. "Extracorporeal Shock Wave Lithotripsy in Patients with Cardiac Pacemakers." The Journal of Urology, vol. 198, no. 6, Oct. 2017, pp. 1249-1255. Article
European Heart Rhythm Association. "EHRA Consensus on Prevention and Management of Electromagnetic Interference on Cardiac Implantable Electronic Devices." European Journal of Cardio-Thoracic Surgery, vol. 61, no. 4, 2 Apr. 2022, pp. 797-803. Open Access
American Urological Association. "Complications of Shock Wave Lithotripsy - AUA Update Series." AUA, May 2025. PDF
Paterson, Robin. "Extracorporeal Shock Wave Lithotripsy in Patients with Pacemakers and Implantable Devices." The Journal of Urology, vol. 198, no. 6, Oct. 2017. Abstract
Chapter on Complications of Extracorporeal Shock Wave Lithotripsy. Abdominal Key, Sept. 2018. Website
McDonnell, Breandan, et al. "Anaesthetic Consideration in Patients with Cardiac Implantable Electronic Devices." BJA Education, vol. 16, no. 12, Dec. 2016. Open Access
Association of Anaesthetists. "Guidelines for the Perioperative Management of People with Cardiac Implantable Electronic Devices." Anaesthesia, vol. 78, no. 8, Aug. 2023, pp. 923-937. Article
Practice Advisory for the Perioperative Management of Patients with Cardiac Rhythm Management Devices. American Society of Anesthesiologists, 19 Aug. 2024. PDF
Schatz, Ira J., et al. "Bilateral Extracorporeal Shock Wave Lithotripsy in a Woman With a Pacemaker." Spine, vol. 25, no. 13, Aug. 1999, pp. 1667-1670. PDF