Flashcards in Chapter 8 Deck (22):
Heart Block Dysrhythmias
The electrical current has difficulty traveling along the nl conduction pathway, causing a DELAY IN OR ABSENCE OF ventricular depolarization. There are three levels of heart blocks. The P-P interval is regular with all heart blocks.
First Degree Atrioventricular Block
Is a DELAY in electrical conduction from the SA node to the AV node, usually around the AV node, which prevents an electrical impulse from traveling to the ventricular conduction system. Similar to being in a traffic jam. The time it takes for the electrical current to stimulate ventricular depolarization is longer than normal
Fist degree atrioventricular block criterial for classification
The PR interval is constant and measures greater than 0.20 seconds, all other measures are WNL
Signs and sx's in fist degree atrioventricular block
Pts will be able to maintain nl cardiac output. No change should occur with pt. It is important to observe the cardiac output parameters to assess the blood supply to the vital organs.
Second Degree Atrioventricular Block
Irregular VENTRICULAR responses. There are two types. This category has some blocked or non-conducted electrical impulses form the SA node to the ventricles at the atrioventricular junction region. As a result there are missing QRS complexes. Depending on the type, the conduction through the AV node may be delayed and at some point blocked in a pattern or the impulse is blocked entirely, resulting in missing QRS complexes.
Second Degree Atrioventricular Block Mobitz I
Type I or Wenckebach: Caused when diseased or injured atrioventricular node tissue conducts the electrical impulse to the ventricular conduction pathway with increasing difficulty, causing a delay in time until one of the atrial impulses fails to be conducted or is blocked. AFTER THE DROPPED ATRAIL IMPULSE, THE ATRIOVENTRICULAR NODE RESETS ITSELF TO BE ABLE TO HANDLE FUTURE IMPULSES MORE QUICKLY AND THEN PROGRESSIVELY GETS MORE DIFFICULT UNTIL IT DROPS OR IS BLOCKED AGIAN. This patterns will repeat itself.
Who discovered Second degree atrioventricular blocks
Dr. Woldemar Mobitz, a German internist. It was then further investigated by Dr. Wenckebach
Second Degree Atrioventricular Block Mobitz I Criteria for Classification
Has a cyclical prolonging PR interval until the QRS is dropped. Then the cycle "resets" and begins again (irregular ventricular response) "lengthen, lengthen, drop"
Signs and sx's in second degree atrioventricular block type 1
Pt may or may not exhibit sx's of decreased cardiac output depending on the rate of ventricle contraction (decreased or =40 bpm)
What caused second degree atrioventricular block type 1?
Inflammation around the atrioventricular node, it a temporary condition that will resolve itself and return to a nl heart rhythm
Tx of second degree atrioventricular block type 1
Monitoring the way pt tolerates rhythm., medication, danger to progress to third degree heart block
Second Degree Atrioventricular Block Mobitz II
Also called classical heart block because it was the first rhythm observed to have an occasional dropped complex. The atrioventricular node selects which electrical impulses it will block. This might be seen as 2. 3. 4 P waves between each QRS complex. Expressed in ration (3:1 second degree type II) FREQUENTLY THIS DYSRHYTHMIA WILL PROGRESS TO THIRD DEGREE ATRIOVENTRICULAR BLOCK.
Main difference between type 1 and type 2 in second degree block
The PR interval in type 1 progressively gets longer and then disappears with a QRS complex and RESETS, type 2 PR intervals are all the same but there is QRS complex that disappears.
Second Degree Atrioventricular Block Mobitz II criteria for classification
QRS complexes are missing, but, wherever a P is with the QRA complex, the PR interval will always measure the same
Signs and sx's of second degree block type 2
Sx's of low cardiac output that could lead to third degree atrioventricular block or complete heart block (CHB) within second.
The classical block can quickly lead to
Third degree block/complete heart block which calls for a Code Blue emergency
Tx for second degree block type 2
Monitoring and temporary external pacemaker
Tips on determining type 1 from type 2
1. Identify missing QRS complexes
2. Analyze PR interval
3. Type 1 will have progressively pronging pattern followed by a missing QRS complex
4. Type 2 will have regular PR intervals with a missing QRS complex
Third Degree Atrioventricular Block (Complete)
(CHB) All electrical impulses originating above the ventricles are blocked and prevented form reaching the ventricles. There is no correlation beween atrial and ventricular depolarization. There will be noticeable and suspicious dissociative properties; namely the P-P and R-R intervals. Atria and ventricles fire at completely different rates, resulting in a variable PR interval. Ventricular rate will be slower than atrial rate.
Third Degree Atrioventricular Block (Complete) Criteria for classification
The P-P and R-R intervals are regular (constant) but firing at different rates, P wave location may be buried within the QRS either before or after the QRS complex
Signs and sx's of CHB
Atria are electrically separated from one another (AV dissociation). There is loss of atrial kick from atria and ventricles firing at different times. Sx's of low cardiac output will be seen, and even LOC.