The electrophysiology of antidromic reentry, a less common phenomenon than orthodromic reentry, remains a poorly understood aspect of the Wolff-Parkinson-White (WPW) syndrome. We used a pacing model of ventricular preexcitation in patients without WPW, so that electrophysiological events in the normal pathway during atrial extrastimulation (A1-A2 technique) could be precisely delineated without...

We determined total right atrial activation sequences during entrainment and termination of flutter induced in dogs with a surgically induced atrial lesion. This type of atrial flutter is due to circus movement of an impulse around the tricuspid valve orifice. We recorded simultaneously from 96 bipolar intracavity electrodes in the right atrium of the isolated, perfused heart. By constructing i...

We studied transient entrainment and interruption of atrioventricular (AV) bypass pathway-type paroxysmal atrial tachycardia in 15 patients during overdrive pacing from selected atrial sites. Overdrive atrial pacing at less than a critically rapid rate for interruption transiently entrained the tachycardia. Transient entrainment was due to repeated early entrance of the wave front from the paci...

Transient entrainment of circus-movement tachycardia utilizing an atrioventricular (AV) bypass pathway was studied in 13 patients (nine with the orthodromic form, two with the antidromic form, and two with both the orthodromic and antidromic forms). All patients had a left-sided AV bypass pathway. Pacing at selected rates faster than the spontaneous rate was performed during the tachycardia at ...

Layer VI is the origin of the massive feedback connection from the cortex to the thalamus, yet its complement of cell types and their connections is poorly understood. The physiological and morphological properties of corticofugal neurons of layer VI of mouse primary visual cortex were investigated in slices loaded with the Ca(2+) indicator fura-2AM. To identify corticofugal neurons, electrical...

The delayed and asynchronous firing of chromatolytic motoneurons in response to group I afferent volleys is shown to be evoked monosynaptically, there being an abnormally long and variable delay between onset of monosynaptic action and generation of impulse discharge. Intensity of monosynaptic excitatory action is reduced, and considerable variability in the form of successively evoked postsyna...