https://en.ecgpedia.org/index.php?title=Mechanisms_of_Arrhythmias&feed=atom&action=historyMechanisms of Arrhythmias - Revision history2024-03-29T12:06:45ZRevision history for this page on the wikiMediaWiki 1.39.5https://en.ecgpedia.org/index.php?title=Mechanisms_of_Arrhythmias&diff=10283&oldid=prevDrj at 12:04, 22 April 20102010-04-22T12:04:52Z<p></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Abnormal impulse formation==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Abnormal impulse formation==</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>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]].</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>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]].</div></td></tr>
</table>Drjhttps://en.ecgpedia.org/index.php?title=Mechanisms_of_Arrhythmias&diff=10281&oldid=prevDrj: /* Re-entry */2010-04-22T11:50:18Z<p><span dir="auto"><span class="autocomment">Re-entry</span></span></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Re-entry===</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Re-entry===</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>[[Image:<del style="font-weight: bold; text-decoration: none;">Re_entry</del>.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).]]</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[Image:<ins style="font-weight: bold; text-decoration: none;">Re-entry</ins>.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).]]</div></td></tr>
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</table>Drjhttps://en.ecgpedia.org/index.php?title=Mechanisms_of_Arrhythmias&diff=10277&oldid=prevDrj: /* Re-entry */2010-04-22T11:48:59Z<p><span dir="auto"><span class="autocomment">Re-entry</span></span></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Re-entry===</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Re-entry===</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>[[Image:Re_entry.<del style="font-weight: bold; text-decoration: none;">png</del>|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).]]</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[Image:Re_entry.<ins style="font-weight: bold; text-decoration: none;">svg</ins>|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).<ins style="font-weight: bold; text-decoration: none;">]]</ins></div></td></tr>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Re-entry is a common cause of arrhythmias. [[#Ventricular tachycardia|Ventricular tachycardia]] and [[#AVNRT|AV-nodal re-entry]] are typical examples. Re-entry can occur when a conduction path is partly slowed down. As a result of this, the signal is conducted by both a fast and a slow pathway. During normal sinus rhythm this generally does not cause problems, but when an extrasystole follows rapidly upon the previous beat, the fast pathway is sometimes still refractory and cannot conduct the signal. Now the following sequence results in re-entry.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Re-entry is a common cause of arrhythmias. [[#Ventricular tachycardia|Ventricular tachycardia]] and [[#AVNRT|AV-nodal re-entry]] are typical examples. Re-entry can occur when a conduction path is partly slowed down. As a result of this, the signal is conducted by both a fast and a slow pathway. During normal sinus rhythm this generally does not cause problems, but when an extrasystole follows rapidly upon the previous beat, the fast pathway is sometimes still refractory and cannot conduct the signal. Now the following sequence results in re-entry.</div></td></tr>
</table>Drjhttps://en.ecgpedia.org/index.php?title=Mechanisms_of_Arrhythmias&diff=9992&oldid=prevKGoldin at 22:31, 27 January 20102010-01-27T22:31:58Z<p></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Abnormal impulse formation==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Abnormal impulse formation==</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Abnormal impulse formation can result in <del style="font-weight: bold; text-decoration: none;">an </del>abnormal frequency, as in symptomatic [[#<del style="font-weight: bold; text-decoration: none;">sinusbradycardia</del>|<del style="font-weight: bold; text-decoration: none;">sinusbradycardia</del>]], but <del style="font-weight: bold; text-decoration: none;">oftenwise </del>the problem is an abnormal location of impulse formation, as is the cause in an [[#ectopic_pacemaker|ectopic pacemaker]].</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Abnormal impulse formation can result in abnormal frequency, as in symptomatic [[#<ins style="font-weight: bold; text-decoration: none;">sinus bradycardia</ins>|<ins style="font-weight: bold; text-decoration: none;">sinus bradycardia</ins>]], but <ins style="font-weight: bold; text-decoration: none;">often </ins>the problem is an abnormal location of impulse formation, as is the cause in an [[#ectopic_pacemaker|ectopic pacemaker]].</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Abnormal automaticity===</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Abnormal automaticity===</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>The sinus node contains pacemaker cells that have spontaneous firing capacity<del style="font-weight: bold; text-decoration: none;">, this </del>is called ''normal automaticity''. '''Abnormal automaticity''' occurs when other cells start firing spontaneously, resulting in premature heartbeats. All cardiac cells have spontaneous firing capacity, but at only at a very slow <del style="font-weight: bold; text-decoration: none;">heartrate</del>. Therefore, during a normal heart rate, they will never have the chance to show off their firing capacity. However in pathologic conditions, such as during extreme bradycardia other cells can take over and cause for example <del style="font-weight: bold; text-decoration: none;">a </del>[[AV nodal rhythm|AV-nodal heart rate]].</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The sinus node contains pacemaker cells that have spontaneous firing capacity<ins style="font-weight: bold; text-decoration: none;">. This </ins>is called ''normal automaticity''. '''Abnormal automaticity''' occurs when other cells start firing spontaneously, resulting in premature heartbeats. All cardiac cells have spontaneous firing capacity, but at only at a very slow <ins style="font-weight: bold; text-decoration: none;">heart rate</ins>. Therefore, during a normal heart rate, they will never have the chance to show off their firing capacity. However<ins style="font-weight: bold; text-decoration: none;">, </ins>in pathologic conditions, such as during extreme bradycardia<ins style="font-weight: bold; text-decoration: none;">, </ins>other cells can take over and cause for example <ins style="font-weight: bold; text-decoration: none;">an </ins>[[AV nodal rhythm|AV-nodal heart rate]].</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{clr}}</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{clr}}</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Triggered activity===</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Triggered activity===</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>During '''triggered activity''' heart cells contract twice, although they only have been activated once. This is often caused by so called ''afterdepolarizations'' (early or delayed <del style="font-weight: bold; text-decoration: none;">afterdepolarisations </del>EADs / DADs) caused by electrical instability in the myocardial cell membrane. A typical example of this is [[Torsade de Pointes]].</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>During '''triggered activity''' heart cells contract twice, although they only have been activated once. This is often caused by so called ''afterdepolarizations'' (early or delayed <ins style="font-weight: bold; text-decoration: none;">afterdepolarizations </ins>EADs / DADs) caused by electrical instability in the myocardial cell membrane. A typical example of this is [[Torsade de Pointes]].</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{clr}}</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{clr}}</div></td></tr>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Re-entry===</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Re-entry===</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>[[Image:Re_entry.png|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 <del style="font-weight: bold; text-decoration: none;">extincts </del>when <del style="font-weight: bold; text-decoration: none;">in </del>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).]]</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[Image:Re_entry.png|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 <ins style="font-weight: bold; text-decoration: none;">becomes extinct </ins>when <ins style="font-weight: bold; text-decoration: none;">it </ins>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).]]</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Re-entry is a common cause of arrhythmias. [[#Ventricular tachycardia|Ventricular tachycardia]] and [[#AVNRT|AV-nodal re-entry]] are typical examples. Re-entry can occur when a conduction path is partly slowed down. As a result of this, the signal is conducted by both a fast and a slow pathway. During normal sinus rhythm this generally does not cause problems, but when an extrasystole follows rapidly upon the previous beat, the fast pathway is sometimes still refractory and cannot conduct the signal. Now the following sequence results in re-entry.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Re-entry is a common cause of arrhythmias. [[#Ventricular tachycardia|Ventricular tachycardia]] and [[#AVNRT|AV-nodal re-entry]] are typical examples. Re-entry can occur when a conduction path is partly slowed down. As a result of this, the signal is conducted by both a fast and a slow pathway. During normal sinus rhythm this generally does not cause problems, but when an extrasystole follows rapidly upon the previous beat, the fast pathway is sometimes still refractory and cannot conduct the signal. Now the following sequence results in re-entry.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div># The atrial signal coming from above is conducted by the slow pathway</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div># The atrial signal coming from above is conducted by the slow pathway<ins style="font-weight: bold; text-decoration: none;">.</ins></div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div># As the signal through the slow pathway reaches the end of the fast pathway, it finds this pathway <del style="font-weight: bold; text-decoration: none;">willing </del>to conduct.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div># As the signal<ins style="font-weight: bold; text-decoration: none;">, going </ins>through the slow pathway<ins style="font-weight: bold; text-decoration: none;">, </ins>reaches the end of the fast pathway, it finds this pathway <ins style="font-weight: bold; text-decoration: none;">able </ins>to conduct.</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div># The signal is conducted through the fast pathway up to the beginning of the slow pathway, which by that time is <del style="font-weight: bold; text-decoration: none;">willing </del>to conduct.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div># The signal is conducted through the fast pathway up to the beginning of the slow pathway, which by that time is <ins style="font-weight: bold; text-decoration: none;">able </ins>to conduct.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div># This circle is perpetuated and a signal generator is created. In the case of [[#AVNRT|AV-nodal re-entry]] this will typically generate a signal at a frequency of 180-250 bpm.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div># This circle is perpetuated and a signal generator is created. In the case of [[#AVNRT|AV-nodal re-entry]] this will typically generate a signal at a frequency of 180-250 bpm.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
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</table>KGoldinhttps://en.ecgpedia.org/index.php?title=Mechanisms_of_Arrhythmias&diff=8569&oldid=prevDrj: /* Re-entry */2008-11-13T10:52:52Z<p><span dir="auto"><span class="autocomment">Re-entry</span></span></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 10:52, 13 November 2008</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Re-entry===</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Re-entry===</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>[[Image:<del style="font-weight: bold; text-decoration: none;">reentry_inititation</del>.png|thumb|'''Re-entry'''. <del style="font-weight: bold; text-decoration: none;">Image </del>A <del style="font-weight: bold; text-decoration: none;">shows </del>two pathways. The signal splits in two at arrival, but no arrhythmia is initiated as the slow signal extincts when in meets the fast signal. However, <del style="font-weight: bold; text-decoration: none;">in image B re-entry is initiated by </del>an extrasystole<del style="font-weight: bold; text-decoration: none;">. The extrasystole follows shortly after </del>the <del style="font-weight: bold; text-decoration: none;">previous signal. The </del>fast pathway is still in a <del style="font-weight: bold; text-decoration: none;">refractory state and blocks </del>the <del style="font-weight: bold; text-decoration: none;">signal</del>. The <del style="font-weight: bold; text-decoration: none;">slow </del>signal reaches the <del style="font-weight: bold; text-decoration: none;">'tail' of the fast path </del>by the <del style="font-weight: bold; text-decoration: none;">time that </del>the fast <del style="font-weight: bold; text-decoration: none;">path</del>'<del style="font-weight: bold; text-decoration: none;">s refractory period is finished</del>. <del style="font-weight: bold; text-decoration: none;">The fast path conducts </del>the <del style="font-weight: bold; text-decoration: none;">signal towards the start </del>(<del style="font-weight: bold; text-decoration: none;">upwards</del>) <del style="font-weight: bold; text-decoration: none;">and the circle completes</del>.]]</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[Image:<ins style="font-weight: bold; text-decoration: none;">Re_entry</ins>.png|thumb|'''Re-entry'''. A <ins style="font-weight: bold; text-decoration: none;">prerequisite for re-entry is the presence of </ins>two pathways <ins style="font-weight: bold; text-decoration: none;">with differing conduction velocities that connect two points, in this case the atria with the ventricles</ins>. The signal splits in two at arrival, but no arrhythmia is initiated as the slow signal extincts when in meets the fast signal. However, <ins style="font-weight: bold; text-decoration: none;">after </ins>an extrasystole <ins style="font-weight: bold; text-decoration: none;">(second image) </ins>the fast pathway is still <ins style="font-weight: bold; text-decoration: none;">refractory and conduction is by the slow pathway, resulting </ins>in a <ins style="font-weight: bold; text-decoration: none;">prolongation of </ins>the <ins style="font-weight: bold; text-decoration: none;">PR interval</ins>. The signal <ins style="font-weight: bold; text-decoration: none;">that </ins>reaches the <ins style="font-weight: bold; text-decoration: none;">His </ins>by the <ins style="font-weight: bold; text-decoration: none;">slow pathway may find </ins>the fast <ins style="font-weight: bold; text-decoration: none;">pathway conducting and return to the atria (third image), resulting in an '''echo beat''</ins>'. <ins style="font-weight: bold; text-decoration: none;">This may set in motion a re-entry pathway through </ins>the <ins style="font-weight: bold; text-decoration: none;">AV node resulting in AV nodal tachycardia </ins>(<ins style="font-weight: bold; text-decoration: none;">fourth image</ins>).]]</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Re-entry is a common cause of arrhythmias. [[#Ventricular tachycardia|Ventricular tachycardia]] and [[#AVNRT|AV-nodal re-entry]] are typical examples. Re-entry can occur when a conduction path is partly slowed down. As a result of this, the signal is conducted by both a fast and a slow pathway. During normal sinus rhythm this generally does not cause problems, but when an extrasystole follows rapidly upon the previous beat, the fast pathway is sometimes still refractory and cannot conduct the signal. Now the following sequence results in re-entry.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Re-entry is a common cause of arrhythmias. [[#Ventricular tachycardia|Ventricular tachycardia]] and [[#AVNRT|AV-nodal re-entry]] are typical examples. Re-entry can occur when a conduction path is partly slowed down. As a result of this, the signal is conducted by both a fast and a slow pathway. During normal sinus rhythm this generally does not cause problems, but when an extrasystole follows rapidly upon the previous beat, the fast pathway is sometimes still refractory and cannot conduct the signal. Now the following sequence results in re-entry.</div></td></tr>
</table>Drjhttps://en.ecgpedia.org/index.php?title=Mechanisms_of_Arrhythmias&diff=2904&oldid=prevDrj: /* Triggered activity */2007-07-23T14:01:30Z<p><span dir="auto"><span class="autocomment">Triggered activity</span></span></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{clr}}</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{clr}}</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Triggered activity===</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Triggered activity===</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>'''<del style="font-weight: bold; text-decoration: none;">Triggered </del>activity''' <del style="font-weight: bold; text-decoration: none;">vuren cellen twee keer</del>, <del style="font-weight: bold; text-decoration: none;">terwijl ze maar één keer gestimuleerd zijn</del>. <del style="font-weight: bold; text-decoration: none;">Dit </del>is <del style="font-weight: bold; text-decoration: none;">meestal het gevolg van zogenaamde </del>''<del style="font-weight: bold; text-decoration: none;">nadepolarisaties</del>'' (early <del style="font-weight: bold; text-decoration: none;">of </del>delayed afterdepolarisations <del style="font-weight: bold; text-decoration: none;">EAD's </del>/ <del style="font-weight: bold; text-decoration: none;">DAD's</del>) <del style="font-weight: bold; text-decoration: none;">door electrische onstabiliteit </del>in <del style="font-weight: bold; text-decoration: none;">de hartcelmembraam</del>. <del style="font-weight: bold; text-decoration: none;">Een typisch voorbeeld hiervan </del>is [[<del style="font-weight: bold; text-decoration: none;">#Torsade_de_pointes|</del>Torsade de <del style="font-weight: bold; text-decoration: none;">pointes</del>]].</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">During </ins>'''<ins style="font-weight: bold; text-decoration: none;">triggered </ins>activity''' <ins style="font-weight: bold; text-decoration: none;">heart cells contract twice</ins>, <ins style="font-weight: bold; text-decoration: none;">although they only have been activated once</ins>. <ins style="font-weight: bold; text-decoration: none;">This </ins>is <ins style="font-weight: bold; text-decoration: none;">often caused by so called </ins>''<ins style="font-weight: bold; text-decoration: none;">afterdepolarizations</ins>'' (early <ins style="font-weight: bold; text-decoration: none;">or </ins>delayed afterdepolarisations <ins style="font-weight: bold; text-decoration: none;">EADs </ins>/ <ins style="font-weight: bold; text-decoration: none;">DADs</ins>) <ins style="font-weight: bold; text-decoration: none;">caused by electrical instability </ins>in <ins style="font-weight: bold; text-decoration: none;">the myocardial cell membrane</ins>. <ins style="font-weight: bold; text-decoration: none;">A typical example of this </ins>is [[Torsade de <ins style="font-weight: bold; text-decoration: none;">Pointes</ins>]].</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{clr}}</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{clr}}</div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"></ins></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Abnormal conduction==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Abnormal conduction==</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Conduction delay===</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Conduction delay===</div></td></tr>
</table>Drjhttps://en.ecgpedia.org/index.php?title=Mechanisms_of_Arrhythmias&diff=2456&oldid=prevDrj: /* Principles of Arrhythmias */2007-06-17T23:23:04Z<p><span dir="auto"><span class="autocomment">Principles of Arrhythmias</span></span></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 23:23, 17 June 2007</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Abnormal impulse formation==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Abnormal impulse formation==</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Abnormal impulse formation can result in an abnormal frequency, as in symptomatic [[#sinusbradycardia|sinusbradycardia]], but oftenwise the problem is an abnormal location of impulse formation, as is the cause in an [[#ectopic_pacemaker|ectopic pacemaker]].</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Abnormal impulse formation can result in an abnormal frequency, as in symptomatic [[#sinusbradycardia|sinusbradycardia]], but oftenwise the problem is an abnormal location of impulse formation, as is the cause in an [[#ectopic_pacemaker|ectopic pacemaker]].</div></td></tr>
</table>Drjhttps://en.ecgpedia.org/index.php?title=Mechanisms_of_Arrhythmias&diff=2454&oldid=prevDrj: New page: =Principles of Arrhythmias= ==Abnormal impulse formation== Abnormal impulse formation can result in an abnormal frequency, as in symptomatic sinusbradycardia, but oft...2007-06-17T23:21:49Z<p>New page: =Principles of Arrhythmias= ==Abnormal impulse formation== Abnormal impulse formation can result in an abnormal frequency, as in symptomatic <a href="#sinusbradycardia">sinusbradycardia</a>, but oft...</p>
<p><b>New page</b></p><div>=Principles of Arrhythmias=<br />
==Abnormal impulse formation==<br />
Abnormal impulse formation can result in an abnormal frequency, as in symptomatic [[#sinusbradycardia|sinusbradycardia]], but oftenwise the problem is an abnormal location of impulse formation, as is the cause in an [[#ectopic_pacemaker|ectopic pacemaker]].<br />
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===Abnormal automaticity===<br />
The sinus node contains pacemaker cells that have spontaneous firing capacity, this is called ''normal automaticity''. '''Abnormal automaticity''' occurs when other cells start firing spontaneously, resulting in premature heartbeats. All cardiac cells have spontaneous firing capacity, but at only at a very slow heartrate. Therefore, during a normal heart rate, they will never have the chance to show off their firing capacity. However in pathologic conditions, such as during extreme bradycardia other cells can take over and cause for example a [[AV nodal rhythm|AV-nodal heart rate]].<br />
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===Triggered activity===<br />
'''Triggered activity''' vuren cellen twee keer, terwijl ze maar één keer gestimuleerd zijn. Dit is meestal het gevolg van zogenaamde ''nadepolarisaties'' (early of delayed afterdepolarisations EAD's / DAD's) door electrische onstabiliteit in de hartcelmembraam. Een typisch voorbeeld hiervan is [[#Torsade_de_pointes|Torsade de pointes]].<br />
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==Abnormal conduction==<br />
===Conduction delay===<br />
Conduction delay can cause a slow heart rate, as happens during [[#AV-block|AV conduction blocks]]. If conduction delay occurs more distally in the heart, i.e. within the ventricles, the QRS complex will widen and a [[Conduction|left or right bundle branch block]] can be seen on the ECG.<br />
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===Re-entry===<br />
[[Image:reentry_inititation.png|thumb|'''Re-entry'''. Image A shows two pathways. The signal splits in two at arrival, but no arrhythmia is initiated as the slow signal extincts when in meets the fast signal. However, in image B re-entry is initiated by an extrasystole. The extrasystole follows shortly after the previous signal. The fast pathway is still in a refractory state and blocks the signal. The slow signal reaches the 'tail' of the fast path by the time that the fast path's refractory period is finished. The fast path conducts the signal towards the start (upwards) and the circle completes.]]<br />
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Re-entry is a common cause of arrhythmias. [[#Ventricular tachycardia|Ventricular tachycardia]] and [[#AVNRT|AV-nodal re-entry]] are typical examples. Re-entry can occur when a conduction path is partly slowed down. As a result of this, the signal is conducted by both a fast and a slow pathway. During normal sinus rhythm this generally does not cause problems, but when an extrasystole follows rapidly upon the previous beat, the fast pathway is sometimes still refractory and cannot conduct the signal. Now the following sequence results in re-entry.<br />
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# The atrial signal coming from above is conducted by the slow pathway<br />
# As the signal through the slow pathway reaches the end of the fast pathway, it finds this pathway willing to conduct.<br />
# The signal is conducted through the fast pathway up to the beginning of the slow pathway, which by that time is willing to conduct.<br />
# This circle is perpetuated and a signal generator is created. In the case of [[#AVNRT|AV-nodal re-entry]] this will typically generate a signal at a frequency of 180-250 bpm.<br />
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