De elektrocardiogrammen van 10 olifanten en van de orka in Harderwijk

Bij 1 kangoeroe met atriumfibrilleren, 10 olifanten met een gezond hart en bij 1 orka-walvis werd het ECG geregistreerd. De uitkomsten van vergelijkend elektrocardiografisch onderzoek bevorderen onze inzichten in een aantal aspecten van de elektrische activiteit van het menselijk hart. Het omgekeerde is eveneens het geval; kennis van de menselijke elektrocardiografie stelt ons in staat bepaalde elektrocardiografische verschijnselen bij andere zoogdieren te interpreteren

Synchronization of the heart

The behaviour of cardiac pacemaker cells bears a resemblance to that of relaxation oscillators. A characteristic property of relaxation oscillators is that they may be synchronized by an external signal, if the latter has a periodicity not differing too much from the spontaneous frequency of the oscillator. In the present study, it is shown that the isolated, perfused, and submerged rat heart can be synchronized by a sinusoidal electrical current through the heart. This synchronization is not to be confused with stimulation, which occurs at higher current densities. Synchronization was also found when the frequency of the synchronizing signal was in the neighborhood of a multiple of the spontaneous frequency of the heart. Synchronization was demonstrated for the SA node as well as for a lower pacemaker, presumably the AV node. The possible role which this type of synchronization may play in spontaneous impulse formation in pacemaker tissue is discussed

On the poor legibility of the captions in musea

n the museum world, designers in general hardly take into account the legitimate wishes of elderly visitors, whose visual acuity is often less than optimal, with regard to the legibility of the captions by paintings or in show-cases. The conditions necessary for letter and word recognition, the influence of illumination, contrast and colour are discussed. Test-cards for use in musea, and the recruiting of a representative test-group of senior citizens, are recommended

On the poor legibility of the captions in musea

n the museum world, designers in general hardly take into account the legitimate wishes of elderly visitors, whose visual acuity is often less than optimal, with regard to the legibility of the captions by paintings or in show-cases. The conditions necessary for letter and word recognition, the influence of illumination, contrast and colour are discussed. Test-cards for use in musea, and the recruiting of a representative test-group of senior citizens, are recommended

Elektrisch demonstratiemodel van de prikkelgeleiding van het hart

Er wordt een (elektronisch) model beschreven, dat dienst kan doen voor onderwijs aan paramedisch personeel en artsen. Het model is in staat de meest voorkomende geleidings- en ritmestoornissen alsmede het normale excitatiepatroon van het hart op eenvoudige wijze na te bootsen en zichtbaar te maken

De contractiliteit van het hart

Een grotere contractie na een extrasystole doet zich bij het geïsoleerde, volgens Langendorff doorstroomde rattehart ook voor, indien de vulling van de kamers of de lengte van het hart niet kunnen toenemen

ECG of the "Newborn" Mouse (Mus domesticus) with Specific Reference to Comparative AV Transmission

The objective of this study was to record the ECG of the smallest living mammal to extend the domain of data for comparative AV-nodal electrophysiologic purposes. These data are needed to establish the relationship between the PR interval and heart size in mammalian species of all sizes. Methods and Results: In recently born mice (age 1.5 to 8 weeks) weighing between 2.5 and 10 g and with estimated heart weights between 15 and 60 mg, ECGs, using bipolar limb leads, were recorded during general anesthesia. The PR interval, representing AV transmission time was about 40 msec, which is quite long for hearts of this size. On the basis of detailed analysis of the data, we postulate the presence of a fixed delay or discontinuous propagation in the AV node not only in newborn mice, but in mammals of all sizes. Conclusion: AV transmission times obtained in mammals (including humans) cannot be explained on the basis of generally accepted, classic AV conduction theories. The acceptance of the presence of a fixed delay in the AV node may ultimately be of value to better understand AV node function during sinus rhythm and supraventricular arrhythmias

Signal analysis of ventricular fibrillation

Signal analysis of electro(cardio)grams during ventricular fibrillation (VF) in dogs and human patients indicates more organization and regularity than the official WHO definition suggests. The majority of the signal is characterized by a power spectrum with narrow, equidistant peaks. In a further classification of the electrograms according to their histogram, autocorrelation function and bicoherency spectrum, VF under "normal" conditions tends to two categories: 1) damping of autocorrelation within 2 sec and symmetrical histogram without significant bicoherencies or 2) asymmetrical histogram with significant bicoherencies. VF under hypoxic conditions shows no damping of autocorrelation, high bicoherencies and flat or two-peaked histogram

Periprocedural Hemodynamic Depression Is Associated With a Higher Number of New Ischemic Brain Lesions After Stenting in the International Carotid Stenting Study-MRI Substudy.

BACKGROUND AND PURPOSE: Carotid artery stenting (CAS) is associated with a higher risk of both hemodynamic depression and new ischemic brain lesions on diffusion-weighted imaging than carotid endarterectomy (CEA). We assessed whether the occurrence of hemodynamic depression is associated with these lesions in patients with symptomatic carotid stenosis treated by CAS or CEA in the randomized International Carotid Stenting Study (ICSS)-MRI substudy. METHODS: The number and total volume of new ischemic lesions on diffusion-weighted imaging 1 to 3 days after CAS or CEA was measured in the ICSS-MRI substudy. Hemodynamic depression was defined as periprocedural bradycardia, asystole, or hypotension requiring treatment. The number of new ischemic lesions was the primary outcome measure. We calculated risk ratios and 95% confidence intervals per treatment with Poisson regression comparing the number of lesions in patients with or without hemodynamic depression. RESULTS: A total of 229 patients were included (122 allocated CAS; 107 CEA). After CAS, patients with hemodynamic depression had a mean of 13 new diffusion-weighted imaging lesions, compared with a mean of 4 in those without hemodynamic depression (risk ratio, 3.36; 95% confidence interval, 1.73-6.50). The number of lesions after CEA was too small for reliable analysis. Lesion volumes did not differ between patients with or without hemodynamic depression. CONCLUSIONS: In patients treated by CAS, periprocedural hemodynamic depression is associated with an excess of new ischemic lesions on diffusion-weighted imaging. The findings support the hypothesis that hypoperfusion increases the susceptibility of the brain to embolism. CLINICAL TRIAL REGISTRATION URL: http://www.controlled-trials.com. Unique identifier: ISRCTN25337470