Effects of fibroblast-myocyte coupling on the sinoatrial node activity: A computational study.

While the sinoatrial node (SAN) is structurally heterogeneous, most computer simulations of electrical activity take into account SAN pacemaker cells only. Our aim was to investigate how fibroblasts affect the SAN activity. We simulated the rabbit sinoatrial node accounting for differences between central and peripheral pacemaker cells, and for fibroblast-myocyte electrical coupling.

Computer simulations of reentrant activity in the rabbit sinoatrial node.

With the aid of detailed computer simulations, we have estimated distributions of membrane potential and ionic currents in the core region of a sinoatrial node reentry. We observe reduced amplitudes of the measured quantities in the core; the core sizes for potential and currents did not always coincide. Simulations revealed that acetylcholine, when applied in the vicinity of unstable reentry, attracted the reentry to become the core and to stabilize its rotation.

Hibernator Citellus undulatus maintains safe cardiac conduction and is protected against tachyarrhythmias during extreme hypothermia: possible role of Cx43 and Cx45 up-regulation.

Background: Most mammals experience cardiac arrest during hypothermia. In contrast, hibernators remain in sinus rhythm even at body temperatures of 0 degrees C.

Objectives: The purpose of this study was to quantify electrical activity and connexin expression in the heart of hibernating Siberian ground squirrel Citellus undulatus.

Spatiotemporal dynamics of damped propagation in excitable cardiac tissue.

Compared to steadily propagating waves (SPW), damped waves (DW), another solution to the nonlinear wave equation, are seldom studied. In cardiac tissue after electrical stimulation in an SPW wake, we observe DW with diminished amplitude and velocity that either gradually decrease as the DW dies, or exhibit a sharp amplitude increase after a delay to become an SPW. The cardiac DW-SPW transition is a key link in understanding defibrillation and stimulation close to the refractory period, and is ideal for a general study of DW dynamics.