Search results for "Heart Conduction System"
showing 3 items of 43 documents
[Effect of flecainide on longitudinal and transverse conduction velocities in ventricular myocardium. An experimental study].
2007
It is known that the effect of flecainide on longitudinal and transverse ventricular conduction velocities depends on the coupling interval. If this is so, whether the longitudinal or transverse direction is predominantly affected could depend on the magnitude of the coupling interval. In order to investigate this hypothesis, we studied the effect of flecainide, 1 micromol/L, on conduction velocities in excised heart preparations from 11 rabbits using a basal cycle length of 250 ms and inserting two extrastimuli at a decreasing coupling interval. Flecainide significantly reduced both conduction velocities. However, the effect increased as the coupling interval decreased for only the longitu…
Intrinsic changes on automatism, conduction, and refractoriness by exercise in isolated rabbit heart.
2001
We have studied the intrinsic modifications on myocardial automatism, conduction, and refractoriness produced by chronic exercise. Experiments were performed on isolated rabbit hearts. Trained animals were submitted to exercise on a treadmill. The parameters investigated were 1) R-R interval, noncorrected and corrected sinus node recovery time (SNRT) as automatism index; 2) sinoatrial conduction time; 3) Wenckebach cycle length (WCL) and retrograde WCL, as atrioventricular (A-V) and ventriculoatrial conduction index; and 4) effective and functional refractory periods of left ventricle, A-V node, and ventriculoatrial retrograde conduction system. Measurements were also performed on coronary…
Differential effects of hypothermia on neuronal efflux, release and uptake of noradrenaline
1972
Isolated rabbit hearts were perfused at 34° (control), 24° or 12°C. The neuronal efflux of noradrenaline after perfusion with the amine for 1 h was depressed at 24° C (Q 10 about 5) in the presence or absence of desipramine; at 12°C the efflux was below the limit of estimation. Moderate reduction of the temperature (24° C) decreased the removal of perfused noradrenaline to about 60% of the control value and caused a 1.7-fold increase of the output of noradrenaline evoked by sympathetic nerve stimulation. It is concluded that the extremely temperature-dependent efflux of noradrenaline across the axonal membrane is not part of the release of noradrenaline evoked by nerve stimulation.