The influence of cycle length on the effective and functional refractory period of the human AV node.

The influence of atrial cycle length on the effective and functional refractory period of the human AV node and atrium is presented. In general, decrements in atrial cycle lengths resulted in a shortening of the refractory period of the atrium and the functional refractory period of the AV node. The effective refractory period of the AV node was not significantly prolonged.

Aortic insufficiency. A result of intermittent migration of aortic valve prosthesis poppet.

A bizarre mechanism of aortic valve incompetence was observed when the occluder of a Braunwald-Cutter aortic valve prosthesis decreased in diameter, volume, and weight, and from time to time fell into the left ventricle. The patient's symptoms were palpitation, coughing, chocking sensations, and fright. An operation disclosed a small, smooth ball with disrupted cloth on all the struts.