Effect of modification of shock-wave delivery on stone fragmentation Talic RF & Rabah DM College of Medicine & king Khalid university hospital King Saud University Riyadh, Saudi Arabia

First generation Lithotriptor  High success rate  Minimally invasive

Second & 3 rd generation lithotriptors  User convenience  Reduced anesthesia requirments  Multi-functionality  Results?

Recent publications evaluating different SWL of renal calculi Retreatment rate (%) Stone free (%) LithotriptorYearStudy 5175 Wolf Piezolith 1991 Cope et al 2156Therasonic1992 Mykulak et al 663 Dornier HM3 1995Cass 2187 Modulith SL Coz et al ND63 Dornier Compact 2002 Lalak et al 674 Dornier Doli S 2003 Johnson et al

Stone clearance is the most important aspect for patients receiving SWL for urinary calculi Kouriefs et al. Ann R Col Surg Eng 2004

Improving SWL results  Patient selection  Prognostic variables  Modification of SW delivery –Shock-wave rate –Shock-wave pulse sequencing –Stone targeting –Dose escalation in SW delivery  Modification of SW treatment strategy –Chemolytic pretreatment –Synchronus bilateral stone SWL

Pressure-wave-form at the focus  Leading shock-wave (compressive force) –Dynamic fracture –Cavitational erosion  Tensile wave

Modification of Shock Wave delivery & Strategy  Shock-Wave Rate Modification  Shock-wave pulse sequencing  Stone targeting  Dose escalation in SW delivery  Chemolytic pretreatment

Shock-wave rate modification FAST RATE

Shock-wave rate modification SLOW RATE

Shock-wave rate modification  Electrohydrolic lithotriptor/Ceramic spheres –0.4-s interval = few large fragments –2.0-s interval = many small fragments Wiskell & Kinn. Br J Urol 1995

Shock-wave rate modification  Econolith 2000/118 Ceramic stones –15,20,22 KV at 30,60,120 &150 sw/min –Improved fragmentation at ↑ KV and slow rate Greenstein & Matzkin. Urology 1999

Shock-wave rate modification  Dornier MFL 5000/ 12 solid stadandarised spherical blaster stones More SW needed at 20 KV to fragment stones at 117 sw/min compared to 60 or 80 sw/min Weir et al. J endourol 2000

Shock-wave rate modification  EDAP piezoelectric lithotriptor/ Human kidney stones –3000 SW at frequencies of 1.25,2.5,5 & 10/sec. –Better fragmentation with SLOWER frequencies Vallancien et al. Eur Urol 1989

Shock-wave rate modification  In-vivo study  Artificial stones in pig kidneys/ PCNL –Stone fragmentation significantly improved at SW rate of 30/min compared with 120/min. Paterson et al. J Urol 2002

Shock-wave rate modification  First clinical study (prospective radomized)  114 patients with ureteric stones  Piezoelectric lithotriptor at a rate of 60 or 240  Success rate was reduced for lower ureteral stones and unchanged for upper ureteral stones with the slower rates Roberts et al. J endourol 1999

Shock-wave rate modification To determine the effect of SWL RATE on the treatment outcome of patients with renal and ureteric stones

Shock-wave rate modification Patients & Methods  A Prospective Randomized Trial  Inclusion Criteria:  Stones Single Radio-opaque Radio-opaque Renal or ureteric Renal or ureteric Not more than 30mm Not more than 30mm  Exclusion Criteria  Bleeding disorders  Distal obstruction  Uncontrolled UTI

Shock-wave rate modification FOLLOW UP  At 3 month visit  KUB ±IVU/US  Success: completely stone free clinically insignificant gravel < 2mm clinically insignificant gravel < 2mm  Statistics: Univariate Analysis chi-square chi-square Fisher’s Exact test Fisher’s Exact test Mann-Whiney test Mann-Whiney test Multivariate Analysis Multivariate Analysis

 150 patients Slow rate = 71 patients Fast rate = 79 patients  Sex 108 (72%) Male 42 (28%) Female 42 (28%) Female  Age 42.1±13.4 years Slow: 41.8±14.8 years Fast: 42.3±12.1 years (P=NS) (P=NS) No of patients (P=NS) SEX Results Shock-wave rate modification

 Stone size: –11.98 ± 6.0 mm –Range = (5-30)  Slow rate: 12.4 ± 5.9  Fast rate: 11.6 ± 6.3 (P=NS) (P=NS) (P=NS) No of patients Side Results

Shock-wave rate modification 5794± ±4519 (P=0.005) Results

Shock-wave rate modification 96.5±56,4 61.9±37.6 (P=0.000) Results

Shock-wave rate modification Results  Success rate Entire group of patients: 141/150 (94%)  Slow rate group: 70/71 (98.5%)  Fast rate group: 71/79 (89.8%) (P= 0.025)

Shock-wave rate modification VARIABLESIGNIFICANCE (P value) SWL rate Stone Length Session number Total Shocks Success Rate

Shock-wave rate modification CONCLUSIONS  Shock Wave Lithotripsy rate has an independent significant impact on the success rate after SWL Treatment  The Enhanced success rate with slow SWL rate treatment is achieved with Less number of shock waves

Shock-wave rate modification  Results are better at a SW rate of 60/min.  Especially in patients with larger stones (namely those who have worse outcome classically) Pace et al. J Urol 2005

Shock-wave rate modification  Efficacy of Slow shock wave rate is established  Enhanced Safety and reduced renal tissue injury → Awaits further studies.

Modification of Shock Wave delivery & Strategy  Shock-wave rate  Shock-wave pulse sequencing  Synchronus twin-pulse technique  Sequential twin – pulse – delivery  Stone targeting  Dose escalation in SW delivery  Chemolytic pretreatment

SW Pulse sequencing modification Synchronus twin-pulse technique  The best angle between the 2 shock tubes was 90 o  Enhanced stone dissintegration with the use of 2 energy sources Sheir et al. J Endourol 2001

SW Pulse sequencing modification Synchronus twin-pulse technique Gross & histologic examination of porcine kidneys showed  renal damage when treated with 2 shock tubes compared to conventional under the table single tube. Gross & histologic examination of porcine kidneys showed  renal damage when treated with 2 shock tubes compared to conventional under the table single tube. Sheir et al. Urology % 34% SF at 14/7 40% Redo- All SF in 1/12 At 1/12 Sheir et al. BJU 2005 (Awaiting prospective randomized studies) Clinical study

SW Pulse sequencing modification Sequential twin – pulse – delivery  HM3 pulse followed, at carefuly timed close interval, by an auxilliary sw from (PEA) pizeo- electric annular array. ↓  (Intensify the collapse of SW induced bubles at stone surfac) Zhou et al. J Urol 2004 Zhou et al. J Urol 2004

SW Pulse sequencing modification Sequential twin – pulse – delivery  20 KV HM3 pulse ( ms interval) 4KV PEA pulse  1500 SW to cylindical Bego stone phantoms  Vessel phantom to mimic renal injury –Consistent rupture after 30 SW at 20KV with original HM3 –No Vessel rupture after 200 SW with combined HM3/PEA Zhou et al. J Urol 2004 Zhou et al. J Urol 2004 HM3HM3/PEA 81.3% 95.2%

Modification of Shock Wave delivery & Strategy  Shock-wave rate  Shock-wave pulse sequencing  Synchronus twin-pulse technique  Sequential twin – pulse – delivery  STONE TARGETING  Dose escalation in SW delivery  Chemolytic pretreatment

Effect of stone motion  Ventilatory motion (50mm)  Focal zone of most lithotriptors (4-15mm)  In-vitro study:  Motorized positioner  Storz Modulith SLX  Gypsum cement stones  Motion > 20mm (75% of SW missed the stone) 75%50% No motion10mm motion Fragmentation Cleveland at al. J Endo urol 2004

Effect of stone motion  Solution:  ? Stone Tracking Device  ? Gating Device –Stops the shock wave that will miss the stone –Decrease injury and maintain stone comminution efficiency

Modification of Shock Wave delivery & Strategy  Shock-wave rate  Shock-wave pulse sequencing  Synchronus twin-pulse technique  Sequential twin – pulse – delivery  Stone targeting  DOSE ESCALATION in SW DELIVERY  Chemolytic pretreatment

Dose escalation in SW delivery In-vitro study HM3 Lithotriptor Begostone phantoms 500 SW at 18 KV 500 SW at 20 Kv 500 SW at 22 KV CE* = 88.7% 500 SW at 22 KV 500 SW at 20 Kv 500 SW at 18 KV CE * = 81.2% 1500 SW 20 Kv CE = 83.5% * P significant Zhou et al. J Urol 2004

CHEMOLYTIC PRE-TREATMENT  Altering the chemical environment of the fluid surrounding stones, it is possible to decrease the surface energy and the concomitant fracture strength of renal calculi Akers SR et al. J Urol 1987

CHEMOLYTIC PRE-TREATMENT  In vitro evidence concludes that wave speed, wave impedance, dynamic mechanical properties and micro hardness of EDTA treated calcium oxalate stones and Tromethamine treated uric acid stones were found to decrease compared to untreated (synthetic urine) control groups Heimbach D et al. J Urol. 2004

CONCLUSIONS  Progress in basic research of SWL allowed urologists to start implementing their better understanding of the mechanisms involved in stone comminution and tissue injury into clinical practice.  Slowing the shock wave rate was shown in prospective randomized clinical trials to enhance patients stone free rates

CONCLUSIONS  In vivo and clinical work is needed to further evaluate the beneficial effects seen in, in vitro studies, with sequential twin pulse delivery and with dose escalation in SWL on stone comminution while simultaneously decreasing side effects.

CONCLUSIONS  This future work may well pave the way for new designs and modifications of existing lithotriptors that will ultimately enhance current stone free rates and minimize tissue injury.

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