Sino-atrial exit block: Difference between revisions
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{{Chapter|Sinus node rhythms and arrhythmias}} | {{Chapter|Sinus node rhythms and arrhythmias}} | ||
[[Image:sa_exit_blok.jpg|thumb|Sino-atrial exit block (more precisely: type II second degree SA exit block)]] | [[Image:sa_exit_blok.jpg|thumb|Sino-atrial exit block (more precisely: type II second degree SA exit block)]] | ||
[[Image:sa_exit_blok2. | [[Image:sa_exit_blok2.png|thumb|Sino-atrial exit block]] | ||
During sino-atrial exit block, the depolarizations that occur in the sinus node cannot leave the node towards the atria. They are blocked. On the ECG this is expressed as a pause. SA exit block can be destinguished from [[sinusarrest]] because the pause in SA exit block is a multiple of the P-P interval that preceded the pause. | During sino-atrial exit block, the depolarizations that occur in the sinus node cannot leave the node towards the atria. They are blocked. On the ECG this is expressed as a pause. SA exit block can be destinguished from [[sinusarrest]] because the pause in SA exit block is a multiple of the P-P interval that preceded the pause. | ||
Revision as of 09:19, 26 November 2007
| This is part of: Sinus node rhythms and arrhythmias |
During sino-atrial exit block, the depolarizations that occur in the sinus node cannot leave the node towards the atria. They are blocked. On the ECG this is expressed as a pause. SA exit block can be destinguished from sinusarrest because the pause in SA exit block is a multiple of the P-P interval that preceded the pause.
Three subtypes can be destinguished:[1]
- Type I second degree (Wenkebach) SA exit block: the P-P interval progressively shortens prior to the pause
- Type II second degree SA exit block: the pause equals approximately 2-4 times the preceding PP interval
- Third degree SA exit block: absence of P waves (can only be diagnosed with an sinus node electrode, during electrophysiological evaluation)