Cardiac Arrhythmias: Difference between revisions

Cardiac Arrhythmias (view source)

Revision as of 10:14, 31 December 2012

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 ===Reentry===
-Reentry or circus movement can arise when an area is slowly conducting thereby still propagating the activation while the rest of the heart depolarizes. When the surrounding myocardium has recovered from this refractory state, and can be stimulated, the impulse in the slow conducting zone can reactivate the heart when it exits the area of slow conduction. This process can repeat itself and thus form the basis of a reentry tachycardia. These areas of slow conduction can be anatomical or functional or a combination of both. Examples of reentry tachycardias are atrial flutter, AVNRT and ventricular tachycardias originating from an infarct zone.<Cite>deBakker</Cite>
+Reentry or circus movement can arise when an activation front is conducted through a 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 myocardium. This process can repeat itself and thus form the basis of a reentry tachycardia. 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. 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</Cite>
 =References=