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 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.     

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.     

The Surgical Anatomy of Tetralogy of Fallot with Pulmonary Atresia Rather than Pulmonary Stenosis

We examined the pertinent surgical features of the anatomy of 56 hearts having tetralogy of Fallot with pulmonary atresia instead of stenosis, or malformations with pulmonary atresia closely related to tetralogy. We took particular cognizance of the pulmonary arterial supply in 15 hearts in which this was derived through systemic-to-pulmonary collateral arteries, dissecting, as far as possible, the bronchopulmonary segmental distribution of the collateral arteries compared to the intrapericardial pulmonary arteries in 11 of these hearts. Two of the hearts had absence of intrapericardial pulmonary arteries, so that a solitary arterial trunk left the base of the heart. Evidence of an atretic subpulmonary infundibulum was found in 40 of the hearts, while such an infundibulum was lacking in the remainder. The pulmonary atresia was muscular in 43 hearts, valvar in 11, while the pulmonary trunk was absent in the other two hearts. In the hearts with collateral arteries, on average 2.6 collaterals were found in each case, varying from two to five per case. Only one of these arose from a brachiocephalic artery, the others all arising from the descending aorta. The distribution of collateral arteries in two cases was remarkably reminiscent of the arrangement of bronchial arteries. As far as could be judged, 16.5 bronchopulmonary segments on average were supplied in each heart, 5.1 exclusively by collateral arteries, 11.8 by intrapericardial pulmonary arteries and an average of 0.64 segments per case having a shared supply.     

Hemodynamic Deterioration Following Radiofrequency Ablation of the Atrioventricular Conduction System

Radiofrequeucy ablation of the atrioventricular conduction system (ACS) has become an estoblished theTapy for patients with drug refroctory atrial fibrillation. We observed eight patients with hemodynamic deterioration ofteT radiofrequency oblotion of the otTioventTicular conduction system. As we found hemodynamic deterioration related to worsening mitral regurgitation, we compared the clinical history, eiectrophysiologicai, ond echocardiographic dato from the patients with hemodynamic deteriorotion and worsening mitral regurgitation (group 1) to those without hemodynamic deterioration and stable mitral regurgitation after the procedure (group 2). Eight out of 108 patients (7.4%) undergoing ablation of the ACS deteriorated hemodynamically with acute pulmonary edema in three and congestive heart failure in five patients occurring at a mean of 3 and 8 weeks, respectively, after the procedure. Three of these patients were referred for mitral valve surgery. Two patients underwent ablation using a left-sided approach. A right-sided approach was used in five patients. In one patient, a left- and right-sided approach was used. Compared to group 2 patients, group 1 patients had significantly higher left ventricular end-diastolic diameters (64 ± 6 mm vs 56 ± 9 mm) at baseline despite similar fractional shortening (32%± Il% vs 34%± 13%), left ventricular end-systolic diameters (43 ± 9 mm vs36 ± 7 mm) and degree of mitral regurgitation (1.4 ± 1.1 vs 1.4 ±0.7) on echocardiographic analysis. Thus, hemodynamic deterioration together with progression of mitral regurgitation is a potential complication of ablation of the ACS (up to 7.4%). Patients with high left ventricular end-diastolic diameters ond moderate mitral regurgitation at baseline seem prone to this complication.     

Unipolar Waveforms and Monophasic Action Potentials in the Characterization of Slow Conduction in Human Atrial Flutter

Anisotropic propagation may be involved in the development of areas of slow conduction in atrial flutter. We evaluated monophasic action potentials (MAPs) and simultaneous unipolar (0.2–400 Hz) and bipolar electrograms from multiple atrial sites of patients undergoing RF ablation of idiopathic atrial flutter. Nine patients (mean age 46 ± 20 years) with typical atrial flutter (one with both types) were studied. Unipolar electrograms with triphasic complexes of small amplitude and with a slow, negative deviation of the baseline preceding the rS deflection indicated transversal conduction in relation to the orientation of cardiac fibers; smooth rS complexes longitudinal conduction; QS complexes onset of activation; and R complexes end of activation or collision. In all patients with typical atrial flutter, slow conduction occurred in the corridor between the inferior vena cava, the tricuspid annulus, and the coronary sinus. Transversal conduction was observed in this area, whereas the remaining sites showed longitudinal conduction. Anatomically guided RF ablation was successful in five patients. Transversal conduction was recorded in all successful sites. In the patient with atypical atrial flutter, slow conduction was noted in the high lateral right atrium, also exhibiting transversal conduction. Ablation at this area terminated the arrhythmia. All the areas of transversal conduction during flutter displayed longitudinal conduction after restoration of sinus rhythm. MAPs were normal in all patients during atrial flutter and sinus rhythm, even at the areas where transversal conduction was recorded. These findings suggest that anisotropic propagation is involved in the genesis of functionally determined areas of slow conduction during typical atrial flutter.