An experimental model for canine visceral leishmaniasis

Seven mixed-breed dogs were challenged with either promastigotes or amastigotes of Leishmania donovani infantum strains recently isolated from naturally infected dogs. Different routes and numbers of parasites were utilized and each dog was monitored for at least 1 year post-infection. Anti-parasite specific antibody levels were measured by enzyme-linked immunosorbence, immunofluorescence, crossed-immune electrophoresis and Western blotting on crude antigen. Western blotting on two pure parasite proteins, dp72 and gp70-2, was also done. Mitogenic and antigen-specific stimulation of peripheral blood lymphocytes was monitored; and the haematological, clinical and parasitological parameters measured. Dogs challenged with amastigotes exhibited a more pronounced humoral response to leishmanial antigens. Only in one case was strong antigen-specific proliferation detected. Clinical signs of disease, including hypergammaglobulinaemia, enlarged lymph nodes and the presence of parasites, were also more apparent in the dogs challenged with amastigotes. None of the seven dogs died. Serum antibodies to leishmanial antigens were apparent between 1.5 to 3 months following challenge and correlated with the appearance of enlarged lymph nodes, hypergammaglobulinaemia and the presence of parasites in tissue biopsies. Serum antibodies remained chronically high in these dogs throughout the period of the study. Only one dog (1/3) challenged intravenously with promastigotes and the dog challenged intradermally with amastigotes produced transient antibody responses to leishmanial antigen.     

Radiofrequency Ablation of Concealed Left Free-Wall Accessory Pathways Without Coronary Sinus Catheterization:

Ablation of Concealed Accessory Pathways. Introduction: Feasibility of radiofrequency (RF) ablation using a two-catheter technique without coronary sinus catheterization was studied in 100 consecutive patients with a single concealed left free-wall accessory path-way.
Methods and Results: Tachycardia was induced by electrical stimulation in the right atrium/right ventricle, and the presence of a concealed left free-wall accessory pathway was suggested electrocardiographically (negative P wave in leads I and/or a VL during orthodromic tachycardia) or by earlier atrial activation in the pulmonary artery compared to the high right atrium. Mapping of the mitral annulus was performed during right ventricular pacing or orthodromic tachycardia, and RF energy was applied at the site with the earliest retrograde atrial activation. Ablation was considered effective if tachycardia could not be induced, and if VA dissociation or exclusive retrograde nodal conduction was observed. Ablation was initially successful in 98 of 100 patients. Mean number of radiofrequency pulses were 3.2 ± 2. Mean fluoroscopy time and total procedure time was 14 ± 9 and 107 ± 32 minutes, respectively. There were no complications related to the procedure. At a mean follow-up of 22 ± 13 months, two patients experienced tachycardia recurrence and required a second procedure, which was successful.
Conclusions: Our results suggest that RF catheter ablation of concealed left free-wall accessory pathways can be safely, effectively, and rapidly performed using a simplified two-catheter technique with no need for coronary sinus catheterization.     

Radiofrequency Ablation of Symptomatic but Benign Ventricular Arrhythmias

Two cases are presented where ablation of severely symptomatic ventricular arrhythmias not responding to medical therapy was accomplished with radiofrequency current application. After a routine programmed stimulation protocol, a quadripolar ablation catheter with a 4-mm tip was advanced percutaneously into the left ventricle in one case and into the right ventricle in the second case; and after precise pace mapping, the arrhythmogenic focus was successfully ablated using radiofrequency current. The postablation ambulatory recording revealed virtual eradication of ventricular ectopy in both cases. In conclusion, in severely symptomatic cases of "benign" ventricular arrhythmias, radiofrequency ablation offers an effective therapeutic alternative.     

Relevance of Atrial Fibrillation Classification in Clinical Practice

Atrial Fibrillation Classification. Use of different classifications for atrial fibrillation reflects the complexity of the arrhythmia and the difficulty in grouping its different aspects. Current classifications are based on clinical presentation, etiology, substrates, mechanisms, etc. From the clinical point of view, the most relevant probably should be one directed at classifying patients in terms of therapeutic options. In this article, a review of known classifications is given, together with an attempt at a new classification based on the possibility of offering a nonpharmacologic treatment to patients.     

Effects of quinidine on ventricular repolarization

The possibility that an asynchronous increase in the ventricularmonophasic action potential duration is the basis of the quinidine-inducedtorsade de pointes, has led us to study the electrophysiologicaleffects of increasing doses of intravenous quinidine. We measuredthe monophasic action potential duration and the ventriculareffective refractory period at several right ventricular myocardialsites in the anaesthetized dog.Our results showed that quinidineinduces a dose-dependent prolongation in ventricular effectiverefractory period and in ventricular monophasic action potentialduration. These increases were uniform throughout the rightventricle. No variations in repolarization or in refractorinesswere observed between the four ventricular sites studied.Theresults suggest that quinidine does not have a direct effecton dispersion of repolarization, and that mechanisms other thanits direct electrophysiological action are involved in the developmentof torsade de pointes.     

Successful Radiofrequency Ablation of an Accessory Pathway During Pregnancy

The preexcitation syndrome is a rare entity during pregnancy. We present a 20-week pregnant patient with Wolff-Parkinson-White syndrome and recurrent episodes of tachycardia with hemodynamic compromise refractory to medical treatment that required electrical cardioversion several times. Due to the poor evolution we performed a successful radiofrequency ablation of a right posteroseptal accessory pathway using 70 seconds of total fluoroscopy time without complications. We consider this is an alternative and safer treatment in those cases in which the tachyarrhythmias compromise the hemodynamic state during pregnancy.