New Electrophysiologic Features and Catheter Ablation of Atrioventricular and Atriofascicular Accessory Pathways:

Catheter Ablation for Mahaim Pathways. Introduction : Several modalities of catheter ablation have been proposed to eliminate Mahaim pathway conduction. However, limited research has been reported on the electrophysiologic nature of this pathway in its entity.
Methods and Results : In seven patients, electrophysiologic study was performed, and radiofrequency energy was applied to investigate the electrophysiologic clues for successful ablation. In all seven patients, the Mahaim pathway was diagnosed as a right-sided atriofascicular or atrioventricular pathway with decremental properties. In two patients, two different kinds of electrograms were recorded through the ablation catheter positioned at the Mahaim pathway location: one was suggestive of conduction over the decremental portion, demonstrating a dulled potential; and the other of nondecremental conduction, demonstrating a spiked potential. All but one of the Mahaim pathways were eliminated successfully at the atrial origin where the spiked Mahaim potential was recorded. Radiofrequency energy application was performed at the slow potential site resulting in failure to eliminate the conduction over the Mahaim pathway. Conduction block at the site between the slow and fast potential recording sites was provoked by intravenous administration of adenosine, concomitant with a decrease in the amplitude of the Mahaim potential. In one patient, the clinical arrhythmia was a sustained monomorphic ventricular tachycardia originating from the ventricular end of the Mahaim fiber.
Conclusion : The identification of Mahaim spiked potentials may be the optimal method to permit their successful ablation. Detailed electrophysiologic assessment is indispensable for successful ablation of tachycardias associated with Mahaim fibers because tachycardias unassociated with Mahaim fibers can occur despite complete elimination of the Mahaim fiber.     

Primary Adrenocortical Carcinoma and Ganglioneuroblastoma Followed by Rhabdomyosarcoma in a Child: A Case Report

We report a case of a young child affected by triple cancerswho developed a pleomorphic rhabdomyosarcoma of the retroperitoneumfollowing prophylactic chemotherapy after surgery for doubleprimary adrenocortical carcinoma and ganglioneuroblastoma. It is suggested that genetic susceptibility and chemotherapymight be responsible for the development of rhabdomyosarcomaas the second malignant neoplasm.     

Four Cases of T-Cell Malignancy in Childhood

Four cases of T-cell malignancy in childhood are reported. Inthe two older boys (seven [Case 1] and eight [Case 2] yearsold) the disease began as leukemia without a clinically detectablemediastinal mass. However, thymic involvement was found at autopsyin Case 1. Tumor cells of both patients had a rosetteformingcapacity with sheep erythrocytes (ERFC), high terminal deoxynucleotidyltransferase (TdT) activity and a positive acid phosphatase (AcPase)reaction. These findings suggest that the tumor cells of Cases1 and 2 originated from thymic T lymphocytes. The two younger patients (two [Case 3] and three [Case 4] yearsold) had cervical lymphadenopathy with mediastinal mass at onset,followed by leukemic change. The youngest patient (Case 3) lackedERFC and the AcPase reaction, but had C3 Receptor (C3-R), humanT-lymphocyte antigen (HLTA) and TdT activity. These findingsindicate that the tumor cells of Case 3 are compatible withearly thymic T lymphocytes. Tumor cells of Case 4 had ERFC,C3-R, HTLA, and slightly increased TdT activity. These findingssuggest that the tumor cells of Case 4 originated from thymicT lymphocytes. Only one patient has maintained an initial complete remissionfor more than one year. The three others relapsed or had a leukemicconversion within 12 months of the initial remission and twodied within 13 months. This indicates that childhood T-cellmalignancies have a poor prognosis.     

Comprehensive treatment of advanced neuroblastoma involving autologous bone marrow transplant

Encouraging results are reported with high-dose chemotherapy and total body irradiation followed by autologous bone marrow transplantation in the treatment of advanced neuroblastoma. However, relapse remains a significant problem. We used high-dose chemotherapy, surgery, intraoperative radiation and an autologous bone marrow transplant treated in vitro to remove tumor cells followed by 13-cis-retinoic acid to treat 36 children with advanced neuroblastoma. This comprehensive treatment appears to improve the survival rate of patients with advanced neuroblastoma, including those with N-myc amplification and bony involvement. The disease-free survival rate was 66% (95% confidence interval, 49–84%) at 3 years. All patients who received 13-cis-retinoic acid developed cheilitis, but no bone marrow depression occurred in these patients. Five patients developed hemolytic uremic syndrome (HUS) post-transplant. This may have been related to the procedure used for total body irradiation. Patients who had their kidneys shielded during this procedure did not develop this syndrome. Patients who received local irradiation at the primary site showed no evidence of relapse in this region, indicating that such therapy may help to prevent a relapse. These data suggest a high rate of 3 year disease-free survival with this treatment strategy. The nonrandomized nature of the study and use of multiple modalities precludes analysis of the specific contribution of each.     

Morphological Variation of Nonreentrant Idiopathic Ventricular Tachycardia Originating from the Right Ventricular Outflow Tract and Effect of Radiofrequency Lesion

RF catheter ablation was performed in 16 patients with nonreentrant idiopathic VT originating from the RVOT. All documented VT was monomorphic, but subtle morphological variation in the VT-QRS complex was observed in 10 (63%) of 16 patients. Through endocardial mapping, VT origin was determined within a narrow site (< 0.5 ± 0.5 cm) in 4 of the 10 patients with the morphological variation. In the other 6 of 10 patients, the origin extended to an area of > 0.5 ± 0.5 cm. In VT with morphological variation, the local electrogram at the site of VT origin also showed variation in morphology and activation sequence. For VT of narrow origin, RF application to the site eliminated the VT. However, in VT from a wide arrhythmogenic area, RF current had to be delivered to 3–7 distinct sites to cover the possible origin, and specific QRS configuration of VT and/or PVC was ablated at each of the earliest activation site. All but one VT were successfully ablated by RF current. Subtle morphological variation was frequent in this type of VT, and about half were associated with a wide arrhythmogenic area. Precise mapping and analysis of the efficacy of each BF application might be helpful to better understand the relationship between subtle changes of VT-QRS morphology and their origins.     

MEDIASTINAL EMPHYSEMA AFTER ESOPHAGEAL ENDOSCOPIC SUBMUCOSAL DISSECTION: ITS PREVALENCE AND CLINICAL SIGNIFICANCE

Aims: To assess the prevalence and clinical significance of mediastinal emphysema (ME) after esophageal endoscopic submucosal dissection (ESD). Methods: A total of 105 patients in whom assessment of ME was prospectively carried out with multi‐detector row computed tomography (MDCT) after esophageal ESD were included in this study. ME was graded as follows: Grade‐0, no ME; Grade‐I, bubbles around the esophagus; Grade‐II, ME around the thoracic aorta; Grade‐III, ME extending around the heart or beyond the mediastinum into the neck; and Grade‐IV, ME with pneumothorax or subcutaneous emphysema. MDCT grading was compared with the finding of conventional chest X‐ray images (CXR) and clinical symptoms. Results: CXR revealed the presence of ME in 6.6% of the subjects. On MDCT, ME was recognized in 62.9% (Grade‐0, 37.1%; I, 46.7%; II, 10.5%; III, 5.7%; and IV, 0%), most (83.8%) being Grade‐I or 0. CXR was able to visualize ME of Grade‐II or greater. Exposure of the muscularis propria layer and location of the lesion were significant risk factors for development of ME of Grade‐II or greater (P = 0.008 and P = 0.03, respectively). The duration of a fever of 37°C or higher was longer and the serum C‐reactive protein level was higher in patients with a higher grade of ME. Conclusions: MDCT revealed the occurrence of ME in 62.9% of the patients who had undergone esophageal ESD, most of which, however, was clinically silent. Exposure of the muscular layer during ESD and location of the lesion were independent risk factors for the development of ME.     

The Use of the Block Cycle Length as a Safe and Efficient Means of Interrupting Sustained Ventricular Tachycardia and Its Pharmacological Modification

In nine patients who had inducible monomorphic sustained ventricular tachycardia (VT), rapid pacing was performed in 11 episodes of morphologically distinct VT at progressively shorter cycle lengths and VT was interrupted at a critical cycle length. The VT interrupting critical cycle length was defined as the block cycle length (BCL) and the effect of Class I antiarrhythmic drugs were examined. Both the VT cycle length (VTCL) and the BCL were prolonged after administration of either drug. The overall mean ratio of the BCL to the VTCL was unchanged after procainamide administration, but increased after the use of mexiletine. The ratio, however, varied in individual VTs and the BCL after treatment with Class I antiarrhythmic drugs could not be predicted from the ratio baseline value, although the ratio was always > 60% and the hazard of VT acceleration might be avoided if the BCL is used.