The cardiac conduction system is a specialized tract of myocardial cells responsible for maintaining normal cardiac rhythm. Given its critical role in coordinating cardiac performance, a detailed analysis of the molecular mechanisms underlying conduction system formation should inform our understanding of arrhythmia pathophysiology and affect the development of novel therapeutic strategies. His...

BACKGROUND The anatomic-electrophysiological correlation of AV nodal reentry is unclear. To localize reentrant circuits during atrial and ventricular echoes and to characterize sites of slow conduction and block, we correlated histology with electrophysiology of the AV node. METHODS AND RESULTS In 10 isolated dog hearts, extracellular electrical activity was recorded in Koch's triangle at 208...

Lidocaine is a commonly used antiarrhythmic drug that causes use-dependent blockade of sodium channels in vitro and reduces conduction velocity in vitro and in vivo. According to the modulated receptor hypothesis of antiarrhythmic drug action, lidocaine has a low affinity for rested sodium channels but a high affinity for open and inactivated channels. In the present experiments, we characteriz...

It was recently shown that supernormal conduction in the diseased His-Purkinje system is more common than previously thought, and is always associated with prolongation of refractoriness. To assess whether supernormal conduction could also occur in the accessory pathway of patients with ventricular pre-excitation, 21 patients with manifestly prolonged refractoriness in the accessory pathway wer...

Premature atrial stimulation was performed during His bundle recording in four patients with the type of ventricular pre-excitation in which theforward H deflection appeared after the onset of the delta wave. The AV conduction patterns occurring in these patients seemed to have depended on the physiological differences existing between normal pathway and accessory pathway (AP) at different mome...

Asynchrony of conduction may prove to be an important mechanism for reentrant arrhythmias. The purpose of these experiments was to explore asynchronous conduction in the distal branches of the canine Purkinje system. Microelectrodes were placed in Purkinje bundle preparations resembling a T configuration, thereby permitting assessment of differential conduction times induced by premature beats ...

Thin sections of canine right and left ventricular endocardium and myocardium were studied in a tissue bath to compare conduction properties of intraventricular specialized conducting tissue [Purkinje fibers (PF)], the superficial layers of subendocardial ventricular muscle (SVM), and the deeper ventricular muscle (DVM) below this level. The study was carried out because of observations that so...

A 'concealed' accessory pathway was suspected in 12 patients because of eccentric left atrial activation during tachycardia. Retrograde conduction during ventricular pacing may occur over the atrioventricular node, the accessory pathway, or both. There were 4 patterns of ventriculoatrial conduction in response to ventricular extrastimuli (V2) at various coupling intervals: (1) exclusive accesso...

BACKGROUND AND PURPOSE Neurolymphomatosis is a rare manifestation of hematological malignancy and is characterized by direct infiltration of the peripheral nervous system. The objective of this study was to identify the clinical and electrophysiological features of neurolymphomatosis. METHODS We retrospectively analyzed the medical records of 13 patients with neurolymphomatosis. Seven (54%) o...

Experiments were performed to test the hypothesis that a reduction in the space constant contributes to slow conduction in the infarcted myocardium of dogs 5-8 days after coronary artery occlusion and reperfusion. Standard microelectrode techniques were used to measure action potential characteristics and conduction velocity parallel to fiber orientation in normal and infarcted ventricular epic...