Does the rate of extracorporeal shock wave delivery affect stone fragmentation?

OBJECTIVES

To evaluate the effect of the rate of shock wave delivery on stone fragmentation, because the optimal rate of shock wave administration has not yet been established.

METHODS

Standard phantom, ball-shaped, ceramic stones were placed in a net-like basket with a hole size of 2.2 mm and immersed in a specially designed water bath coupled with the Econolith 2000 lithotripter. One hundred eighteen stones (mean diameter 9.5 mm) were used. Shock waves were delivered at rates of 30, 60, 90, 120, and 150 shocks/min and at intensities of 15, 20, and 22.5 kV (electrohydraulic). The number of shocks required for complete fragmentation, determined by all fragmented particles falling through the basket holes, was recorded.

RESULTS

The most effective (fewer shocks needed for complete stone fragmentation) rate of shock wave delivery was 60 shocks/min. A statistically significant difference was demonstrated between the mean number of shocks required for complete stone fragmentation at the rate of 60 shocks/min and faster rates at all energy levels (P <0.01) but not between the rate of 60 shocks/min and the rate of 30 shocks/min at all energy levels.

CONCLUSIONS

The rate of shock wave administration during extracorporeal shock wave lithotripsy seems to influence stone disintegration. We demonstrated that extracorporeal shock wave lithotripsy is most effective when waves are delivered at 60 shocks/min.