Monday, October 31, 2011

EKG Rhythm Strips 15: Sinus Rhythms

Identify the following sinus rhythms
1.
2.
3.

4.
5.

6.

7.
8.


9.
10.


Answers:

1.
Sinus Arrhythmia

Sinus Arrhythmia.   The rhythm is irregular.  There is one upright P wave for each QRS complex. The rate is between 60-100.  The rhythm is determined by measureing the distance between the adjacent R waves, called the R-R interval.  If the rhythm is regular, the R-R interval should be the same.  With sinus arrhythmia, the difference between the shortest and longest R-R interval is over 0.12. sec. and the PR interval should be the same.  Some normal rhythmic variation occurs with respirations.  The heart rate speeds up slightly with inspiration and decelerates with expiration.

2.
Normal Sinus Rhythm

Normal Sinus Rhythm.  The rhythm is regular.  There is one upright P wave with each QRS complex.  the PR interval is < 0.12 sec.  There are no ectopic beats.  The rate is 79.  A PR interval > .20 seconds is characteristic of what heart block?

3.
Sinus Bradycardia
Sinus Bradycardia.   The rhythm is regular.  There is one upright P wave associated with each QRS complex.  The PR interval falls within normal range.  What is the normal PR interval?  There are no ectopic beats.  The rate is < 60 beats/min.  

4.
Sinus Bradycardia

Sinus Bradycardia. The rhythm is regular. There is one upright P wave associated with each QRS complex. The PR interval falls within normal range.  There are no ectopic beats. The rate is < 60 beats/min.   What do you notice about the ST segment?  The normal ST segment is flat, isoelectric.  Could be indicative of some ischemia or an electrolyte disorder. 

5.
Normal Sinus Rhythm
Normal Sinus Rhythm. The rhythm is regular. There is one upright P wave with each QRS complex. the PR interval is < 0.12 sec. There are no ectopic beats. The rate is 65 beats/min.

6.
Sinus Rhythm with Sinus Arrest

Sinus Rhythm with Sinus Arrest.  Except for the pauses, the rhythm is regular.   There is one upright P wave for each QRS complex.  The PR interval is 0.16 sec.  There are no ectopic beats.   One cause for the sinus arrest may be sick sinus syndrome.  If theses pauses occur frequently causing the patient to be unstable, then immediate transcutaneous pacing is indicated.  What are some other possible cause of unstable bradycardia?   (Think Hs&Ts).  

7.
Sinus Arrhythmia

Sinus Arrhythmia.   The rhythm is irregular. There is one upright P wave for each QRS complex. The rate is between 60-100.   In this rhythm strip,  the difference between the shortest and longest R-R interval is over 0.12. sec. and the PR intervals should be the same. 

8.
Sinus Tachycardia

Sinus Tachycardia. The rhythm is regular. There is one upright P wave with each QRS complex. the PR interval is < 0.12 sec. There are no ectopic beats. The actual rate is ____ beats/min.    Sinus tachycardia is a symptom of some underlying problem:  anxiety, fever, pain, dehydration and so forth.   Always look for the underlying cause.   How would you distinguish between SVT and sinus tachycardia?   With Sinus tachycardia the rate is between 100-150.   With SVT the rate is usually over 150.   With sinus tachycardia there are identifiable P waves.   In SVT the P waves are not generally seen.   With sinus tachycardia, you can usually relate it to a primary cause.  When you treat the cause, the rate slows down.   However, with SVT it may not be related to a primary cause such as fever, activity, or pain.   It is usually sustained, though it may occur in paroxsyms.  With sinus tachycardia the electrical impulse from the SA node follows the usual conduction pathway.  But with SVT, the electrical impulse gets caught in an reentry pathway.    Let me pick you brain some more.   What medication is indicated for the treatment of SVT?   One are the initial and subsequent dosages?   Describe the technique for administering the medication?   Hint:  it has a very short half life.

9.
Bradycardia with Sinus Arrhythmia
Bradycardia with Sinus Arrhythmia. The rhythm is irregular. There is one upright P wave associated with each QRS complex. The PR interval falls within normal range and the PR intervals are the same. There are no ectopic beats. The rate is < 60 beats/min.  If the P waves were of different morphology and the PR intervals were different then you would expect the arrhythmia to be ectopic in origin.   What is the difference between the shortest and longest P-P interval?  

10.
Sinus Rhythm with Sinus Arrest
Sinus Rhythm with Sinus Arrest.  As above (#6), except for the pause, the rhythm is regular. The is one upright P wace for each QRS complex. The PR interval is 0.16 sec. There are no ectopic beats. 
How many seconds does the pause last?   Physiologically, this represent an abrupt cessation in blood flow so the patient may experience a syncopal episode.  


Reviewed 2/28/16

Saturday, October 29, 2011

EKG Rhythm Strips 14: Junctional Rhythms

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3.


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5.


6.

7.
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9.






10.







Answers
1.
Junctional rhythm





Junctional rhythm.  The rhythm is regular.  There are P waves but they are inverted and the QRS complexes are narrow (< .12 sec).  What is the rate?   This is the factor for determining which junctional rhythm you are looking at.  Junctional rhythms arise from around the AV junction.  The inherent rate of AV junctional area is 40-60 and the rhythm is called a junctional rhythm.  When the rate is between 60-100 it is called an accelerated junctional rhythm and it is called junctional tachycardia when the rate exceeds 100 beats per minute.  The characteristics of a junctional rhythm is that the rhythm is regular.  The P wave may be absent or be present but inverted and precede or follow the QRS complex.  The QRS complexes are usually narrow. 
2.
Junctional Tachycardia






Junctional Tachycardia.  The rhythm is regular.  What is the rate?   Recall that you can either count the number of QRS complexes in a 6 second strip and mulitiply that number by 10 in order to determine the rate.  Each small square is 0.4seconds.  Each larger square is 0.2 seconds.  So 5 large squares equals one second.  The small hash marks at the bottom of the strip represents 3 seconds.  Now that you know how to determine the rate, what is the rate and what is the rhythm?
3.
Junctional Rhythm





Junctional Rhythm.  Actually this rhythm strip is a little slower than a normal junctional rhythm.  But anything is possible when dealing with a sick heart.  But it shows some good characteristics of a junctional rhythm.  The inherent rate of the junctional tissue is______?   The junctional tissue is inferior to the SA node and the atrium in the conduction pathway.   So in order to activate the atrium, the impulse arising from the AV junction has to travel northward (antegrade).   On the electocardiogram this will appear as a negative (inverted) P wave.  If the atrium are depolarized before the ventricles then the inverted P wave will appear before the QRS complex.   If the atrium and ventricles are depolarized at the same time, then the P wave will be absent.  If the atrium are depolarized after the ventricles then the inverted P wave will appear after the QRS complex.  In this rhythm strip the P wave follows the S wave (the small hump at the begining of the T wave).  The P wave appears upright but this is not the case. As the T wave begins to rise and become more positive, you will see that it is interupted by a negative deflection, this is the negative P wave.
4.
Junctional Rhythm







Junctional Rhythm.  What is the rate?  Is the atrium or ventricle depolarized first?   This is a slow rhythm and the patient may be symptomatic or unstable or even pulseless.  If the patient is pulseless, proceed using the PEA alorithm.  If the patient is unstable: think immediate transcutaneous pacing.  While setting up for pacing the MD may try Atropine 0.5mg or a catecholamine infusion with Dopamine or Epinephrine.  What is the dosage range for Dopamine?   Dopamine is a positive inotrophic agent will dilate the renal and messentary arteries at lower dose and cause increase myocardial contractility and vasoconstriction at higher doses.   Thus, the MD might have you start at a dose of 5mcg/kg/min or higher in order to increase cardiac ouput and heart rate.
5.
Junctional Tachycardia





Junctional Tachycardia.   The rate is 125 so this puts it in the range of being a junctional tachycardia.  The ventricles are depolarized first so the inverted P wave follows the QRS complex.  A patient will not usually begin to be symptomatic until a heart rate gets over 150 (there are always exceptions).  In general a junctional rhythm does not respond to cardioversion.  Unlike SVT where the mechanism is a re-entry problem, a junctional rhythm arises from an escape mechanism.   Whereas cardioversion can be used to interupt and break the re-entry cycle, it generally has no effect on rhythms that ectopic in nature.  What is another fast ectopic rhythm?  Hint:  The rate is over 100 and it has a least 3 P waves of varying morphology?  Hmmmm?
6.
Accelerated Junctional Rhythm





Accelerated Junctional Rhythm.   The rhythm is regular.  There are no P waves.  The QRS complex is narrow.  Based upon the rate (what is the rate?) it is called an accelerated junctional rhythm.  Where are the P waves?  (See answer for rhythm 3 above)   Notice that the QRS complex is narrow.  This occurs because the ventricles are depolarized along the normal conduction pathway.  If the QRS complexes in this rhythm strip were wide (>.12 sec) then you would probably say that the rhythm was ventricular in orgin.  In which case it would be called an accelerated  ______  rhythm?  Hint:  it is characterized by a wide QRS complex with a rate between 40 and 100).


7.
Accelerated Junctional Rhythm







Accelerated Junctional Rhythm.  Based upon the rate of 69, this rhythm is properly identified as an accelerated junctional rhythm.  There are P waves present and they are inverted before the QRS complex.  They almost resemble delta waves.  In what rhythm are delta waves associated with? 

8.
Accelerated Junctional Rhythm




Accelerated Junctional Rhythm.   The rhythm is regular.  The rate is 88.  The P waves are inverted and the QRS complex is narrow.  The inverted P waves suggests a rhythm that is junctional in nature.

9.
Junctional Rhythm






Junctional Rhythm.   The rhythm is regular.  The P waves are inverted and follow the QRS complex.  Based upon the slow rate, the rhythm is properly identified as a junctional rhythm.  If the patient were hypotensive, cold and clammy, confused, short of breath, and had chest pain, how would you treat the patient? 

10.
Junctional Tachycardia




Junctional Tachycardia.  The rhythm is regular.  The P waves are inverted and follow the QRS complex.  The QRS complex is narrow.  Because the rate is > 100, this rhythm is readily identified as junctional tachycardia.   As the rate approaches 150 the QRS complexes get closer and closer together and the P waves may not be evident at all.  If the patient were symptomatic only, you might try some vagal manuvers in order to treat or identify the rhythm.  Recall that vagal maneuvers are both theraputic and diagnostic.  What are 5 vagal maneuvers you could try?   What are the restrictions for using carotid sinus massage?


Reviewed 2/28/16


Friday, October 28, 2011

EKG Rhythm Strips 13- Heart Blocks

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02.

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04.
05.

06.

07.
08.
09.

10.




Answers
01.
Sinus Rhythm With 1st Degree AV Block

Sinus Rhythm With 1st Degree AV Block.  This block is characterized by a PR interval that is greater than .20 sec.  The rhythm is usually regular.  There is one P wave for each QRS complex (no dropped beats).  What is the actual PR interval in this strip? 

02.
3rd Degree Heart Block

3rd Degree Heart Block  or Complete Heart Block is identified by P waves and QRS complexes that do not occur together.  Recall that in a sinus rhythm there should be one P wave for each QRS complex and that the PR interval should be < .20 seconds.   In most cases, structually there is a block below the level of the AV node so this prevents electrical impulses by the SA node from reaching the ventricles. Thus, an escape mechanism comes into play and the ventricular rate will be dependent upon a junctional focus (40-60) or ventricular focus (20-40).
It is well worth mentioning the pacemaker rule for the heart.  The Pacemaker Rule:  the fastest rate controls the heart.
1. This is usually the SA node unless an irritable foucs is faster: called irritability
2. If an upper pacemaker fails, then the lower pacemakers (junctional or ventricular) assumes control: escape beat or rhythm

03.
Sinus Rhythm With 1st Degree AV Block

Sinus Rhythm With 1st Degree AV Block.  Again the PR interval is over > 0.20 sec.  The rhythm is regular except for the PVCs  The rate is 75.  The PR interval is ___?  The QRS is < .12.   QT .44.     What does the PR interval represent?   There are also two unifocal PVCs present.

04.
2nd Degree Heart Block Type II (Mobitz II)
2nd Degree Heart Block Type II (Mobitz II).  When you look at the rhythm strip you see that there are P waves that are not immediately followed by QRS complexes.  These P waves are referred to as nonconducted P waves or nonconducted beats.  These nonconducted beats are atrial in orgin but they are not conducted down the conduction pathway of the heart to the ventricles.  Usually there is a block below the level of the AV node that prevents them from reaching the ventricles.  When you see nonconducted beats:  Think no cardiac output- no blood flow. 

05.
2nd Degree Heart Block Type II (Mobitz II)
2nd Degree Heart Block Type II (Mobitz II).  As above,  there are nonconducted P waves but then there are some P waves that are followed by QRS complexes that appear sinus in origin.   On these conducted beats there is one P wave for each QRS complex.  The PR interval is constant, usually less than 0.20 sec. and the R-R interval is also constant.  This is important to remember when trying to distinguish  a Mobitz I from Mobitz II block.  On a Mobitz II block the PR interval on the conducted beats will be the same whereas on a Mobitz I block the PR interval progressively lengthens.

06.
2nd Degree Heart Block Type I (Mobitz I or Wenchebach)
2nd Degree Heart Block Type I (Mobitz I or Wenchebach).  The rhythm is irregular.  There is no one P wave for each QRS complex and the PR interval progressively lengthens.  Usually this occurs in cycles on the rhythm strip where you will have 3 or 4 beats that is followed by a nonconducted P wave.  Usually this block occurs at the level of the AV node.   What coronary artery profuses the AV node?  What kind of MI would you likely see this block in?  Inferior?  Anterior?  Lateral? 

07.
3rd Degree Heart Block
3rd Degree Heart Block.  In looking at this rhythm strip, you immediately notice that there are P waves that do not match up with the QRS complexes.  This should clue you in to the fact that the Atrium and Ventricles are not beating in synchronization.  Calculate the atrial rate and the ventricular rate.   Are they the same?  If you measure the P-P interval you will see that there are some P waves that are buried within the QRS complexes. 

08.
2nd Degree Heart Block Type II (Mobitz II)
2nd Degree Heart Block Type II (Mobitz II).  As you look at this rhythm strip, you see that there are more P waves than QRS complexes.  There are actually 3 P waves for each QRS complexes so you might see this referred to as a 3:1 conduction.  What is the atrial rate? (Measure the number of small boxes between the P waves and divide that number into 1500)  What is the ventricular rate?   With a slow rate, there is an insufficient amount of blood being pushed into the systemic circulation by the ventricles so the patient may be symptomatic (dizzy, light headed, feel weak) or unstable (short of breath,  cold and clammy, have chest pain, hypotensive).  If the patient is only symptomatic- think medications.  If the patient is unstable- think electrical interventions: pacing.  Use Atropine cautiously in Mobitz II and complete heart blocks as it may worsen the block.  The AHA now recommends catecholamine infusions as an acceptable substitute for pacing.  What are the catecholamines infusions and what is the dosage range?  What is the dosage of Atropine?  What is the maximum cumulative dose of Atropine?

09.
2nd Degree Heart Block Type I (Mobitz I or Wenchebach)
2nd Degree Heart Block Type I (Mobitz I or Wenchebach).  There is progressive lengthening of the PR interval in the conducted beats and this is followed by a nonconducted P wave.  This is rarely a serious block.  

10.
3rd Degree Heart Block
3rd Degree Heart Block.  Now that you know how to measure the P-P interval and the R-R interval, determine the atrial rate and the ventricular rate.  This block occurs below the level of the AV node somewhere near the septum. You might see this kind of block with involvement of the LAD artery.  What kind of MI would you see with LAD involvement?  Inferior?  Anterior?  Lateral?   Let us say that our patient is unstable and that the MD decides to try transvenous pacing on the patient with this heart rhythm.  What is the correct places to place the comb pads?   What is the difference between a demand pacing mode (synchronous) and non-demand (asynchronous) mode.   What is meant by the term pacing threshold?  How would you assess for mechanical capture?   : )

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Reviewed 2/28/16