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Mechanisms of Arrhythmias: Difference between revisions
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[[file:arrhythmia-mechanisms.svg|thumb|Mechanisms of arrhythmias]] | |||
==Abnormal impulse formation== | ==Abnormal impulse formation== | ||
Abnormal impulse formation can result in abnormal frequency, as in symptomatic [[#sinus bradycardia|sinus bradycardia]], but often the problem is an abnormal location of impulse formation, as is the cause in an [[#ectopic_pacemaker|ectopic pacemaker]]. | Abnormal impulse formation can result in abnormal frequency, as in symptomatic [[#sinus bradycardia|sinus bradycardia]], but often the problem is an abnormal location of impulse formation, as is the cause in an [[#ectopic_pacemaker|ectopic pacemaker]]. | ||
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===Re-entry=== | ===Re-entry=== | ||
[[Image: | [[Image:Re-entry.svg|thumb|'''Re-entry'''. A prerequisite for re-entry is the presence of two pathways with differing conduction velocities that connect two points, in this case the atria with the ventricles. The signal splits in two at arrival, but no arrhythmia is initiated as the slow signal becomes extinct when it meets the fast signal. However, after an extrasystole (second image) the fast pathway is still refractory and conduction is by the slow pathway, resulting in a prolongation of the PR interval. The signal that reaches the His by the slow pathway may find the fast pathway conducting and return to the atria (third image), resulting in an '''echo beat'''. This may set in motion a re-entry pathway through the AV node resulting in AV nodal tachycardia (fourth image).]] | ||
[[Image:re-entry2.svg|thumb]] | [[Image:re-entry2.svg|thumb]] | ||