Effects of High-frequency Current on Pacemakers during Endoscopic Gastric Surgery: Experimental Study

Abstract: This study examined the effects of high-frequency current on pacemakers. Pacemakers were implanted in mongrel dogs, gastric mucosal resection was performed endoscopically using monopolar and bipolar snares, and the times for resection and magnitude of interference current (IC) in the myocardial electrodes were compared. The time for resection was 9.56±2.87 seconds with a monopolar snare and 0.82±0.13 seconds with a bipolar snare (p<0.01). The magnitude of the IC was 0.59±0.26 mV with a monopolar snare and 0.26±0.12 mV with a bipolar snare (p<0.01). The times required for resection and the magnitude of the IC using a bipolar snare in the coagulation mode at an output of approximately 12 W were 1.97±0.65 seconds and 0.03±0.02 mV, respectively, and those in the cutting mode were 1.68±0.50 seconds and 0.07±0.04 mV, respectively. The magnitude of the IC was significantly less (p<0.01), but the time required for resection was longer in the coagulation mode. No abnormalities were noted in the pacemaker mode in any of the 10 pacemakers examined after mucosal resection with high-frequency current at an output of 300 W. These results suggest that endoscopic therapy using high-frequency current can be performed more safely with a bipolar snare than with a monopolar snare in patients with pacemakers. In addition, the selection of the endoscope mode is considered to be important. (Dig Endosc 1999; 11: 150–157)     

Electrophysiological Findings in Idiopathic Recurrent Ventricular Fibrillation: Special Reference to Mode of Induction, Drug Testing, and Long-Term Outcomes

Electrophysiological studies can be useful in the presence of idiopathic ventricular fibrillation (VF) and may be used when selecting antiarrhythmic drugs. However, the yield, the mode, and the long-term reproducibility of the induction of VF have not yet been fully elucidated. Eight patients with idiopathic VF underwent electrophysiological study. The mean age (± SD) was 45 ± 17 years. Six were males and two were females. Diagnosis was done by exclusion. VF was induced in 6 (75%) of 8 patients using double extra stimuli at coupling intervals of 233 ± 39 and 191 ± 20 ms for the first and second extra stimuli, respectively. Of note, VF was induced by stimulation exclusively at the origin of the premature ventricular beat, which was the first complex of VF in two patients. In another patient, VF was initiated by two premature stimuli and also by a pause produced by rapid pacing. The inducibility of VF was reproduced 9–18 months after the first induction in all of the four patients studied. When the ability of antiarrhythmic drugs to suppress VF inducibility was confirmed, no recurrence was observed during the follow-up period of 40–160 months, but a recurrence of VF was observed in one of two nonresponders. In one patient, amiodarone administration failed in preventing VF induction 9 months after initiation of therapy, and reassessment of long-term drug-efficacy might be indicated in some patients. In conclusion, idiopathic VF was highly inducible (75%) with double extra stimuli. In this study, it was induced from a specific site (2/8) or by a pause (1/8). Induction of VF seemed to be reproduced 9–18 months after the first study. The outcome was considered favorable when the inducibility of VF was suppressed by antiarrhythmic drugs.     

Successful Radiofrequency Current Catheter Ablation of Sustained Ventricular Tachycardia

We performed radiofrequency current catheter ablation in two patients with nonischemic sustained ventricular tachycardia (VT). In one patient, two morphologically distinct VTs were induced by electrical stimulation. One showed right bundle branch block pattern and the other left bundle branch block pattern. The earliest site of activation during each VT was determined at the septum of the right ventricle. However, these two sites were close to the His-bundle elecfrogram recording area. In the other patient, a VT with a left bundle branch block pattern occurred spontaneously after the administration of isoproterenol. The earliest site of activation during VT was determined at the outflow tract of the right ventricle. During tachycardia, radiofrequency current ablation (40 W ± 30 sec) was delivered to the earliest site of activation, A few seconds after fulguration, each VT was terminated and additional radio-frequency currents were given near these sites. After the ablation, VT could not be induced by the electrical stimulations, nor did it recur. No side effects were observed and the atrioventricular conduction remained intact. We feel that nonischemic VTs could possibly be treated by using radiofrequency current catheter ablation.     

Preparation and opioid activities of N-methylated analogs of [D-Ala2, Leu5]enkephalin

Analogs of opioid pentapeptide [D-Ala², Leu⁵]enkephalin were prepared using two kinds of N-methylation reactions, namely quaternization and amide-methylation. Quaternization reaction with CH³I-KHCO³ in methanol was applied to the deprotected N-terminal group of the pentapeptide derivatives affording trimethylammonium group-containing analogs. [Me₃⁺ Tyr¹,D-Ala², Leu⁵]enkephalin and its amide were found to show opioid activity on guinea pig ileium assay only slightly lower than the parent unmethylated peptides. Application of amide-methylation reaction using CH₃I-Ag₂O in DMF to the protected pentapeptide yielded a pentamethyl derivative in which all of the five N atoms were methylated. Deprotection of the derivative gave pentamethyl analogs of [D-Ala², Leu⁵]enkephalin, which showed no significant activity on the guinea pig ileum assay and opiate-receptor binding assay.     

Efficacy of hypothermic perfusion using University of Wisconsin solution in extended hepatectomy with hepatic inflow occlusion in a canine model

This study was designed to elucidate the efficacy of University of Wisconsin (UW) solution for preventing liver injury, when used as a hypothermic perfusate infused into the systemic circulation during extended hepatectomy with hepatic inflow occlusion. Adult mongrel dogs (9.5–17.5 kg, n= 14) were subjected to 75% hepatectomy under 60 min hepatic inflow occlusion. The animals were divided into two groups. The UW group (n= 7) underwent hypothermic perfusion using 4°C UW solution (core temperature of the liver: 12.3±0.2°C). The control group designated as the Ringer's lactate (LR) group (n= 7) underwent hypothermic perfusion using 4°C LR solution. The perfusate was introduced into the systemic circulation via the hepatic vein. Blood from the hepatic vein was sampled, and alanine amino-transferase, purine nucleoside phosphorylase activities and the ammonia concentration were measured. The 7 day survival rate was higher in the UW group than in the LR group. The parameters of liver function were less significantly altered in the UW group than in the LR group. The plasma ammonia concentration was significantly (P<0.05) lower 6h after reperfusion in the UW group than in the LR group. A small volume of hypothermic perfusion of the liver using UW solution was safe if it returned to systemic circulation. Hypothermic perfusion of the liver using UW solution may be effective for preventing hepatic tissue injury during extended hepatectomy with hepatic vascular occlusion.     

Retroperitoneoscopic pyeloplasty: Using reconstructive methods based on intraoperative findings

AIM: Reconstructive laparoscopic procedures have been recognized as a less invasive treatment than conventional open procedures. However, although the laparoscopic pyeloplasty has also been accepted as useful, few findings have been reported relevant to the retroperitoneal approach. To elucidate its effectiveness and safety, laparoscopic surgery via the retroperitoneal approach was examined in our institution. Furthermore, the importance of laparoscopic observation for ureteropelvic junction and urine passage ureteropelvic junction without indwelling ureteral stent. METHODS: Between July 1998 and December 2004, 13 men and 15 women underwent laparoscopic retroperitoneal surgery for ureteropelvic junction obstruction. The mean patient age was 33.6 years (range: 13-70 years). Methods of repair were determined by intraoperative findings for the relationship between the ureteropelvic junction and surrounding vessels. An indwelling ureteral stent was removed before initiating laparoscopic operation to observe the relationship between ureteropelvic junction and aberrant vessels more precisely. RESULTS: An aberrant renal vessel was found in 13 patients (46%). Dismembered pyeloplasty was carried out in 21 patients, Y-V plasty in five patients and Hellstrom technique in two patients. Ureteral transposition was not required in dismembered pyeloplasty cases. All patients achieved retroperitoneoscopic pyeloplasty without open conversion. The mean operative time was 272 min (range: 155-490 min). The mean estimated blood loss was 44 mL (range: 10-200 mL). No major complications were observed during the intraoperative period, but urinary tract infection occurred in two patients in the postoperative period. In all patients except one, obstruction was improved or resolved. CONCLUSIONS: Laparoscopic retroperitoneal surgery is not only able to repair ureteropelvic junction obstruction, but can also be done safety and less invasively. We believe that laparoscopic observation without indwelling stent will contribute to a more appropriate choice of pyeloplasty.     

Mucoid pseudocyst of the obturator nerve

A 71-year-old man visited the outpatients' clinic of National Saitama Hospital, Japan, complaining of pain in the right leg. Magnetic resonance imaging (MRI) revealed a cystic mass adjacent to the right side of the urinary bladder. He underwent the removal of the cystic mass and the pathological diagnosis was a mucoid pseudocyst of the obturator nerve. After tumor resection, the pain was diminished and he has been free of disease for 3 years.