Reentry Arrhythmia

Excerpt

Reentry describes a self-sustaining cardiac rhythm abnormality. In reentry, the action potential propagates in a circus-like closed loop manner. It is a disorder of impulse conduction and thus describes one kind of arrhythmogenesis and is differentiated from disorders of impulse generation such as automaticity and triggered activity. First studies investigating reentry are over 100 years old and go back to Mines and Garrey. Dysrhythmias based on the reentry mechanism include atrial tachyarrhythmias such as atrial flutter (AFlut), atrioventricular nodal reentry (AVNRT), atrioventricular reentry (AVRT) like Wolff-Parkinson-White (WPW) syndrome and ventricular reentry such as bundle branch reentry (BBR). The pathophysiologic importance of reentry and utility as a treatment target in atrial fibrillation (AFib) is part of ongoing research.

The main task of the heart is to produce cardiac output. Therefore myocardiocytes contract in a highly orchestrated and rhythmic manner. Proper electro-mechanic coupling (EMC) translates electric stimulation into contraction. The action potential runs from the sinus node (SN) via right atrial pathways through the atrioventricular node (AVN) and the His bundle down the Purkinje fibers (His-Purkinje system, HPS) to the ventricular myocardium. Cells are either in an excited or resting condition. From the resting potential, the cell is depolarized until the crossing of a critical threshold, which then causes an action potential (AP). Following the action potential, there is a period of refractoriness (refractory period, RP) when another trigger cannot activate the cell. Wavelength (WL) or cycle length (CL) is the time between two action potentials.