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AV Conduction: Difference between revisions
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==Second degree AV block== | ==Second degree AV block== | ||
In second degree AV block not all p-waves are being followed by QRS complexes: beat dropout occurs. Second degree AV block can be categorized in 3 types: | In second degree AV block not all p-waves are being followed by QRS complexes: beat dropout occurs. Second degree AV block can be categorized in 3 types: | ||
===Second degree AV block type I(Wenckenbach)=== | ===Second degree AV block type I (Wenckenbach)=== | ||
In second degree AV block type I, the PQ interval prolongs from beat to beat up until the drop-out of one QRS complex. The characteristics of a Wenkebach block: | In second degree AV block type I, the PQ interval prolongs from beat to beat up until the drop-out of one QRS complex. The characteristics of a Wenkebach block: | ||
* QRS complexes cluster (e.g. a 5:4 block or 4:3 block) | * QRS complexes cluster (e.g. a 5:4 block or 4:3 block) | ||
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The conduction disturbance in a type I block originates in the AV node. Isolated second degree AV block type I is relatively benign and not a pacemaker indication. | The conduction disturbance in a type I block originates in the AV node. Isolated second degree AV block type I is relatively benign and not a pacemaker indication. | ||
{{clr}} | {{clr}} | ||
===Second degree AV block type II(Mobitz)=== | ===Second degree AV block type II (Mobitz)=== | ||
[[Image:Rhythm_Mobitz.png|thumb| Second degree AV block type II (Mobitz)]] | [[Image:Rhythm_Mobitz.png|thumb| Second degree AV block type II (Mobitz)]] | ||
In second degree AV block type II, beats are dropped irregularly without PQ interval prolongation. As the drop out of beats is irregular, no clustering of QRS complexes can be seen as in second degree block type I. Second degree AV block type II marks the starting of trouble and is a class I pacemaker indication. <cite>CITATION</cite> | In second degree AV block type II, beats are dropped irregularly without PQ interval prolongation. As the drop out of beats is irregular, no clustering of QRS complexes can be seen as in second degree block type I. Second degree AV block type II marks the starting of trouble and is a class I pacemaker indication. <cite>CITATION</cite> | ||
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===High grade AV block=== | ===High grade AV block=== | ||
High grade AV block is defined as two or more p-waves not followed by QRS complexes. | High grade AV block is defined as two or more p-waves not followed by QRS complexes. | ||
==Third degree AV block== | ==Third degree AV block== | ||
[[Image:Rhythm_3rdAVblock.png|thumb| 3rd degree AV block. AV dissociation is present: there is no relation between p-waves and the (nodal) QRS complexes.]] | [[Image:Rhythm_3rdAVblock.png|thumb| 3rd degree AV block. AV dissociation is present: there is no relation between p-waves and the (nodal) QRS complexes.]] | ||