Heart Blocks Interpretation | SA block, AV block, intraatrial block

Heart Blocks Interpretation | SA block, AV block, intraatrial block

Block - is an obstacle that is located on any part of the conduction system of the heart and makes it difficult for impulses and excitation to pass through it.

These obstacles may either slow (notice how the impulse slows up)

or at all close the way for the impulses to path (notice how there is no excitation at all)

SA-blocks!

SA-blocks are of three degrees: I degree, II degree and III degree

I degree SA-block
In first degree SA-block, the impulse arising from the SA-node to the atrium in slowed up, which oftenly occurs due to problems in the transition zone, which is shown in the figure by a curved arrow.

II degree SA-block
Unlike the first degree SA-block, where the impulse in the transition zone only slows down, but in the case in the II degree SA-block, the pulse periodically either does not appear at all in the SA node,or arises, but does not have enough force, to pass through the transition zone -

III degree SA-blocks
during the third degree of the SA-block, not a single impulse arising in the SA-node reaches to the atria
Because of that, theoretically, an isoline should be recorded on the ECG - in other words - cardiac arrest

Interatrial block
due to intra-atrial blocks, an obstruction occurs on these paths that slows up the conduction of the impulse - it passes more slowly
Atrioventricular block (AB - block).
AV blockades are also of three degrees:
-I degree
-II degree
-III degree

Criteria for I degree AV block:
-PQ interval more then 0.2 sec
-or PQ segment more then 0.1 sec

Criteria for second type of the II degree AV block (Mobitz 2) :
-P wave are always normal
-PQ intervals are the same
-QRS complex periodically drops out

Criteria for the first type of the II degree AV block (Mobitz 1):
-P wave are in normal
R-R intervals are the same
-QRS complex periodically drops out
-progressive lengthening of PQ intervals before falling out of the QRS complex

Criteria of III degree AV block :
-P-P intervals are the same; one rhythm
-R-R intervals are the same; different rhythm
there are no relationships between the appearance of P waves and QRS complexes - we notice a complete disconnection between the atria and the ventricles