Initiation and dynamics of a spiral wave around an ionic heterogeneity in a model for human cardiac tissue

In relation to cardiac arrhythmias, heterogeneity of cardiac tissue is one of the most important factors underlying the onset of spiral waves and determining their type. In this paper, we numerically model heterogeneity of realistic size and value and study formation and dynamics of spiral waves around such heterogeneity. We find that the only sustained pattern obtained is a single spiral wave anchored around the heterogeneity. Dynamics of an anchored spiral wave depend on the extent of heterogeneity, and for certain heterogeneity size, we find abrupt regional increase in the period of excitation occurring as a bifurcation. We study factors determining spatial distribution of excitation periods of anchored spiral waves and discuss consequences of such dynamics for cardiac arrhythmias and possibilities for experimental testings of our predictions

Global alternans instability and its effect on non-linear wave propagation : dynamical Wenckebach block and self terminating spiral waves

The main mechanism of formation of reentrant cardiac arrhythmias is via formation of waveblocks at heterogeneities of cardiac tissue. We report that heterogeneity and the area of waveblock can extend itself in space and can result formation of new additional sources, or termination of existing sources of arrhythmias. This effect is based on a new form of instability, which we coin as global alternans instability (GAI). GAI is closely related to the so-called (discordant) alternans instability, however its onset is determined by the global properties of the APD-restitution curve and not by its slope. The APD-restitution curve relates the duration of the cardiac pulse (APD) to the time interval between the pulses, and can easily be measured in an experimental or even clinical setting. We formulate the conditions for the onset of GAI, study its manifestation in various 1D and 2D situations and discuss its importance for the onset of cardiac arrhythmias

Feliene idiopathische cystitis

Aandoeningen van de lagere urinewegen bij de kat, frequent benoemd met de term feline lower urinary tract disease (FLUTD), vormen een veel voorkomend klinisch probleem. De term FLUTD omvat verschillende aandoeningen die de urineblaas en urethra bij katten aantasten en waarvan de belangrijkste oorzaak idiopathische FLUTD (iFLUTD) of feliene idiopathische cystitis is. De laatste jaren werden verschillende risicofactoren en mogelijke etiologische factoren van iFLUTD geïdentificeerd. Naast abnormaliteiten ter hoogte van de urineblaas zelf wordt de pathogenese van iFLUTD ook gekenmerkt door een overmatige stimulatie van het sympathisch zenuwstelsel en een afgezwakte endocriene respons. De diagnose van iFLUTD kan pas gesteld worden na de uitsluiting van alle andere gekende oorzaken van FLUTD. Omgevingsverrijking, stressreductie, blikvoer en andere strategieën om de wateropname te verhogen vormen de voornaamste behandelingsmethoden van iFLUTD. Het hoge risico op recidieven en de potentieel letale gevolgen van een urethrale obstructie verklaren de onvoorspelbare en soms gereserveerde prognose

The use of desoxycorticosterone pivalate in dogs with hypoadrenocorticism : a retrospective study of eight cases

In this article, the use of desoxycorticosterone pivalate is retrospectively reviewed in eight dogs with primary hypoadrenocorticism, presented at the Small Animal Department of Ghent University. The results showed that desox corticosterone pivalate provided adequate mineralocorticoid replacement in all cases, also in the dogs that had previously been treated with fludrocortisone acetate. A starting dosage of 1.5 - 2.2 mg/kg SC was used, with a fixed dosing interval of 28 days in most of the cases. Each time, prednisolone was added to the therapy as glucocorticoid supplementation. No side effects related to desoxycorticosterone pivalate therapy were noted and all owners were satisfied with the treatment consisting of desoxycorticosterone pivalate and prednisolone

De rol van ervaring bij de beoordeling van urinesediment bij hond en kat

Urinalysis plays an important role in diagnosing several diseases and as part of routine health checks of senior and geriatric patients. There is no solid data regarding the role of experience in the microscopical examination of urine sediment of small animals. The purpose of this study was to investigate the role of experience when examining urine sediment. In total, sediment of 27 urine samples (of 13 dogs and 14 cats) were microscopically examined independently by one experienced observer (the expert) and two unexperienced final-year, veterinary students. For most sediments, there was a weak agreement (low kappa value: 0-0.4) between the expert and the students, with the exception of a moderate agreement for struvite crystals (kappa value: 0.47). The agreement between the students was also weak, but slightly higher than the agreement between the expert and the students. In this study, it is shown that experience plays an important role in the correct examination of urine sediment