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Cardiac Arrhythmias: Difference between revisions
→Disorders of Impulse Conduction
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==Disorders of Impulse Conduction== | ==Disorders of Impulse Conduction== | ||
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 ( | ===Conduction block=== | ||
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 (pathophysiological) conditions or can be iatrogenic (medication, surgery). | |||
===Re-entry=== | ===Re-entry=== | ||
Re-entry or circus movement is a multicellulair mechanism of arrhythmia. 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 can arise when an impulse enters the circuit, follows the circular pathway and is conducted through an unidirectional (slow conducting) pathway. Whilst the signal is in this pathway the surrounding myocardium repolarizes. If the surrounding myocardium has recovered from the refractory state, 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 re-entry 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> | Re-entry or circus movement is a multicellulair mechanism of arrhythmia. 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 can arise when an impulse enters the circuit, follows the circular pathway and is conducted through an unidirectional (slow conducting) pathway. Whilst the signal is in this pathway the surrounding myocardium repolarizes. If the surrounding myocardium has recovered from the refractory state, 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 re-entry 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> | ||