[Electroconductive extracorporeal lithotripsy with Sonolith 4000+. A prospective study of the ECG desynchronization using a fixed-rhythm simulator].

Introduction: Electrohydraulic lithotripters use a R-wave triggering system as episodes of cardiac arrhythmia were observed during early clinical experiments. This study was designed to assess the safety of non triggered shock wave treatments using an external fixed rate device (120/min) on the Sonolith 4000 Plus (*), a non bathtub electroconductive lithotripter.

Methods: Our study is the first prospective evaluation of non-EKG-gated lithotripsy where the patient under continuous Holter monitoring served as his own control during a randomized alternation of periods with or without R-wave triggering. This design allowed for a direct comparison of the effect of EKG-gated and non-EKG-gated lithotripsy respectively. The sequence of the different periods was randomly assigned. The recordings were compared to a pre-treatment recording, the cardiologist ignoring the randomization.

Results: 25 consecutive patients without cardiac history have been treated for urinary stones. Ventricular and supraventricular excitability disorders have been noted in 7 patients, always during a non-EKG-triggered period. There was no correlation with stone location. No cardiac rhythm disturbances have been observed during triggered periods in the 25 patients. Auricular extrasystoles (0.1-0.5/min) were observed in 6 patients, and auricular couplets (0.5/min) in one. Ventricular extrasystoles were noted in 4 patients, and ventricular couplets in one. One patient had an asymptomatic non sustained ventricular tachycardia which resolved spontaneously. No clinically significant disorder occurred. Treatment time and analgesics requirements were reduced by non-EKG-triggering.

Conclusions: Non-EKG-triggering lithotripsy has a definite potential for cardiac disturbances, but appeared to be clinically safe in these patients with no cardiac history.