585
edits
Cardiac Arrhythmias: Difference between revisions
→Re-entry
| Line 70: | Line 70: | ||
Conduction block or conduction delay is a frequent cause of bradyarrhythmias, however tachyarrhythmias can also result from conduction block when this block produces a re-entrant circuit. Conduction block can develop in different (physiological) conditions. | Conduction block or conduction delay is a frequent cause of bradyarrhythmias, however tachyarrhythmias can also result from conduction block when this block produces a re-entrant circuit. Conduction block can develop in different (physiological) conditions. | ||
===Re-entry=== | ===Re-entry=== | ||
Re-entry or circus movement can arise when an activation front is conducted through | Important criteria for the development of re-entry are a circular pathway with an area in this circle of unidirectional block and a trigger to induce the re-entry movement. Re-entry or circus movement can arise when an activation front is conducted through an unidirectional (slow conducting) pathway thereby still propagating the activation while the rest of the surrounding myocardium depolarizes. When the surrounding myocardium has recovered from the refractory state, and can be stimulated again, the impulse that exits the area of unidirectional block can reactivate this recovered myocardium. This process can repeat itself and thus form the basis of a reentry tachycardia. Slow conduction and/or a short refractory period facilitate re-entry. The reason of unidirectional block can be anatomical (atrial flutter, AVNRT, AVRT) or functional (myocardial ischemia) or a combination of both.<Cite>deBakker,Janse</Cite> | ||
=References= | =References= | ||