UNGATED MEDSTONE OUTPATIENT LITHOTRIPSY

Ungated lithotripsy has raised the specter of possible cardiac arrhyth mias, We reviewed ungated outpatient lithotripsy performed on 82 patie nts to evaluate the incidence of arrhythmias encountered and time save d. All patients were chosen in a random nonselected, prospective fashi on. All treatments were performed on a mobile Medstone 1050 STS lithot riptor. The incidence of arrhythmias was 21%. All but 2 arryhthmias we re benign and all reversed with gating. No arrhythmias occurred during treatment of right ureteral stones. In the left ureter only 1 patient had benign premature ventricular contractions during treatment. Arrhy thmias occurred at 20 to 24 kv. in 20% of patients with right renal st ones and 31% with left renal stones. Ah arrhythmias resolved with gati ng. No arrhythmias were encountered at an energy level of less than 20 kv. There was no evidence of electrocardiographic changes up to 1 hou r after treatment. Pharmacological manipulation to maintain a heart ra te of 100 may allow a treatment time of approximately 24 minutes. With ungating the rate may reach 120, allowing for a treatment time of app roximately 20 minutes. In this series average ungated lithotripsy time was 36 minutes. In comparison, the average treatment time in 20 patie nts undergoing gated lithotripsy was 38.7 minutes. It is not clear fro m this study whether persistent ungated lithotripsy would have precipi tated any life threatening arrhythmias since our practice has been to terminate the procedure and re-gate the shocks at the first sign of an y persistent change in cardiac rhythm. Our data indicate that ungated lithotripsy with the Medstone device is safe when simple monitoring ru les are followed.