AIM/DESIGN A concept analysis of concealed pregnancy was undertaken using Walker and Avant's framework to examine the attributes, characteristics and uses of the concept in maternity care. BACKGROUND Understanding the concept of concealed pregnancy is critical as failing to do so adds the risk of maternal and neonatal morbidity and mortality. Reviewing the literature and selected empirical re...

Calcium channel blockers depress atrioventricular (AV) nodal properties in vivo in a frequency-dependent manner, suggesting that selective drug action during supraventricular arrhythmias may result from use-dependent properties. The present study was designed to examine whether or not the rate-dependent actions of diltiazem account for its therapeutic effects during atrial fibrillation. The det...

We used intracellular microelectrodes to study the electrophysiological effects of combinations of components of ischemia and their relation to the occurrence of ventricular arrhythmias in the specialized conducting system of isolated canine right ventricles. The middle area of the free wall was exposed to various test solutions in the center compartment of a three-chambered bath; the base and ...

• The mechanism of irregular ventricular responses to atrial fibrillation has not been established. If atrioventricular transmission occurred via a single path with uniform properties, ventricular cycle lengths would be governed by the refractory period of the path and the temporal pattern of the input supplied by the fibrillating atria. Since the frequency of stimuli available to the A-V condu...

Serial autocorrelation functions and histograms of R-R intervals in patients with atrial fibrillation, with and without digitalis, at rest and during exercise, were produced by a computer. At rest with and without digitalis the first and higher order coefficients did not differ from zero. During exercise (also with and without digitalis) only the first autocorrelation coefficient became slightl...