References

Brashers, V. L.  (2006).  Alterations in cardiovascular function.  In K. L.
         
           McCance and Huether, S. E. (Eds), Pathophysiology: The biologic
          
           basis for disease in adults and children (5th ed., p. 1081-1146). St.
         
           Louis, MO: Elsevier

Critical Care Nursing (2008).  Critical care nursing made easy (2nd ed.).
         
          Ambler, PA: Lippincott Williams & Wilkins

Thaler, M. S. (2003).  The only EKG book you'll ever need (4th ed.). 
          
         Philadelphia, PA: Lippincott Williams & Wilkins

EKG Scenario: can you identify what is going on?

A 68 year old male walks into the ER with his right hand holding his chest.  He is diaphoretic, feeling nauseated, and tells the triage nurse that his chest feels like an elephant is sitting on it.  The nurse takes him back to a room and hooks him up to a 12-lead EKG monitor.  This is the rhythm she sees:   

What do you see on this EKG?  Is there ST depression, STelevation, or no ST elevation. Does this mean there is ischemia, injury, or infarction?  What is going on with this rhythm?  What is the rate?  See if you can answer these questions and let Marna know.  If you have any questions ask Marna.   

               

Can we calculate the rate?

Now that we have learned how to read EKGs, let's learn how to calculate the heart rate.  It is very simple.  Each large box has 5 small boxes with each small box equal to .04.  5x.04= 0.2.  Each large box = 0.2 seconds each.  1 second = 5 cycles or beats per minute (bpm) ( 1 divided by 0.2 = 5 ).  Then 1 minute equals 300 cycles of heart beats or beats per minute (5 x 60 seconds = 300).  If each R wave to R wave measures one large box then the heart rate is 300 bpm.  2 large boxes = 150 bpm (0.2 + 0.2 = 0.4), 3 large boxes = 100 bpm, 4 large boxes = 75 bpm, 5 large boxes = 60 bpm, and 6 large boxes = 50 bpm.  The easiest way to count the rate of this rhythm is to look at the R wave and the heavy long line (start/red arrow).  Count each large box between each R wave.  In this strip there are almost 4 boxes between each R wave. 4 large boxes = 75 and it is just shy of 4 large boxes therefore this heart rate is approximately 75-80 bpm.  Understanding the rate of a rhythm can tell alot about what kind of rhythm it is.  We will discuss the different rhythm rates another time.  Another way to make it easy is to count the R to R wave large boxes and divide the number of boxes into 300.  For example, this R to R wave is 4 large boxes therefore, 300 divided by 4 = 75. 
Here is another way to do a rapid heart rate count.

Using the formula above, can you see how we arrived at the rhythm rates you see?  Look at the following rhythms below and try to figure out the rhythm rates.  If you have any questions, feel free to ask Marna.

Can you identify the rate and rhythms?

Electrical system, ST elevation, and lead placement

When we look at an EKG, the electrical system of the heart is what we are seeing.  Please note how the electrical system functions.  The way the EKG leads are placed on the body is how the electrical system is read.  The following diagram shows the limb lead and precordial lead positions and what is seen on the EKG. 

 Leads II, III, and AVF are the inferior leads and look at the inferior surface which is the right side of the heart. When there is ST elevation in these leads then there is an  inferior injury or myocardial infarction (MI) to the heart.  It is considered an ST elevation MI or STEMI.  Leads I, AVL, V5, and V6 are lateral leads.  When you look at the EKG and see ST elevation in these leads it is a left lateral wall MI as the EKG view is looking at the left lateral side of the heart.  Leads V1, V2, V3, and V4 view the anterior portion of the heart and when there is ST elevation in these leads it is considered an anterior MI as the EKG looks at the left ventricle which is the front of the heart. V1 and V2 also lies over the right ventricle and septum of the heart and are considered to be the leads for the septal portion of the heart.  Therefore, an injury or MI showing injury to V1, V2, V3, and V4 is considered an anterioseptal MI.  

When there is an understanding of the EKG lead placement and the electrical system of the heart and where each lead is looking at the heart it makes understanding the connection of what part of the heart the EKG is viewing easier.  When there is ST elevation in certain leads, there is a greater understanding of what part of the heart is having the injury take place. 

Continue to practice reviewing EKGs and look for EKGs that have ST elevation and look at those particular leads to see if you can tell what area of the heart is being affected.                     

Now that we understand what a PQRST is, the anatomy function that occurs to produce each letter, and some actual rhythms, let's try to understand an EKG and what leads affect what part of the heart.  On a 12-lead EKG, there are 6 limb leads which include 3 standard leads and 3 augmented leads. The 3 standard leads are: Lead I, Lead II, and Lead III by placing 2 electrodes, one on each arm and 2 electrodes, one on each leg.  The 3 augmented leads are somewhat different.  Any of the three leads can be positive and the other two negative with their average serving as the negative electrode or common ground.  Lead AVL, Lead AVR, and Lead AVF.  Lead AVL is created with left arm positive and the other limb leads negative, lead AVR is created with right arm positive and the other limb leads negative, and AVF is created with the legs being positive and the other limb leads negative.   There are also 6 precordial or chest leads arranged across the chest in a horizontal plane.  They are: V1, V2, V3, V4, V5, and V6 and are placed in specific areas on the chest.  V1is placed 4th intercostal space (ICS) to the right of the sternum, V2 placed 4ICS to the left of the sternum, V3 between V2 and V4, V4 placed 5ICS at midclavicular line, V5 placed between V4 and V6, and V6 placed 5ICS at the midaxillary line.  I understand this is a lot of information but please watch the video and you will understand better.  When the video is finished, please try on your own to mark the areas where the leads should be placed.  We will continue the 12-lead EKG in the next session.  If you have any questions please feel free to ask Marna!

Can you tell me the differences?

This is what sinus arrythmia sounds like.  Can you hear the difference between sinus arrthymia and normal sinus rhythm?  Please listen to both videos and explain the difference between the sounds and rthythms. What do you think can cause a sinus arrhythmia? 

                      

Rhythms and rationale? Anyone?

Sinus Arrythmia

 Can anyone identify why this is a sinus arrythmia?  How do you count the ways?

Normal Sinus Rhythm

Sinus bradycardia

How is this normal sinus rhythm different from sinus brady and sinus arrythmia?





What makes this rhythm sinus bradycardia?

Can anyone identify the rate of each rhythm? 
How do we determine the rhythm?
How do we count?

For those of you who can answer these questions, please feel free to leave your answers on the blog and we can discuss them next time. 

Review and What's Ahead

Now that we have the basics out of the way, let's take a moment and review.
EKGs can tell us a lot about a patient.  An EKG should be done on every patient that complains of chest.  Knowing how to interpret them may save someone's life.  For every P wave there should be a QRS followed by a T wave.  Knowing what the PR interval, ST segment and QT interval are can tell us whether the rhythm is normal, there is injury or ischemia, or if there may be  medication affecting the rhythm. 

Tomorrow we will begin to look at normal sinus rhythms, sinus brady, and what asystole and look at some atrial  arrhythmias.  Please feel free to review the videos to stay up on what we have just learned.  Any questions, feel free to ask Marna.

How do they measure?

Ekg rhythm's have a certain measurement for every  PR interval, QRS width, ST segment and the QT interval on Ekg paper. The PR interval typically measures 0.12 to 0.2 seconds, QRS typically measures 0.06 to 0.1 seconds,  ST segment if elevated 1mm or greater is ST elevation and means there is active injury taking place. If there is ST depression there is ischemia that has occurred.  QT interval measures the time it takes for the ventricles to depolarize an repolarize to the ventricular repolarization. For more information on this topic please see: http://geekymedics.com/body-systems/cardiology/understanding-an-ecg/. 
This Ekg grip can show the rhythm strip paper and what each box measures.  One small box measures 0.04 seconds.  There are 5 small boxes measuring 0.04 in one large box.  0.04 x 5= 0.2 seconds.  When looking at rhythms and measuring them these boxes are an important component of measurements and rhythm rate.  Please review this grid and see the example rhythm strips below.  Can you identify the PR interval, QRS width, ST segment and is it ST elevation or ST depression and the QT interval? If you have any questions feel free to ask Marna.

Putting it all together

Can you identify the PQRST, PR, QT, and ST parts of this EKG?  What do the lines on the paper help determine?  Does anybody have any experience in reading EKGs?  If you do, what is this rhythm?  How do you know? What identifying features does this rhythm have?  We will discuss the large and small blocks on the paper and what they represent the next time we meet. 

PR, ST, QT

The PR interval measures the time from the start of atrial depolarizationto the start of ventricular depolarization.  The PR interval includes the P wave and the straight line connecting it to the QRS complex. 
The ST segment measures the time from the end of ventricular depolarization to the start of ventricular repolarization.  The ST segment is the straight line connecting the end of the QRS complex with the beginning of the T wave.
The QT interval measures the time from the beginning of ventricular depolarization to the end of ventricular repolarization.  The QT interval includes the QRS complex, the ST segment, and the Twave.
Why are these intervals and segments important?  Please take time to review some of the videos provided in the blog header to understand these important elements of an EKG.  Please review the following site for more info. 
http://www.nottingham.ac.uk/nursing/practice/resources/cardiology/function/normal_duration.php

PQRST an electrical event

An EKG is an electrical waveform recording that records each cardiac cycle of contraction (systole) and relaxation (diastole).  These electrical events are what produce the basic waves and lines of the standard EKG.  Please see below.  The P wave is produced by atrial contraction or depolarization represented by the upward curve of the image below.  The QRS is produced by ventricular contraction or depolarization which is represented by the next wave which may have several variations.  This electrical waveform begins with a downward deflection or the Q wave, the next and first upward deflection or the R wave, and the next downward deflection after the upward deflection is called the S wave.  The T wave is the electrical representation of the ventricles end of depolarization and the start of ventricular repolarization or relaxation. 

 



Notice in the EKG strip on the right the locations of the PQRST.  For more information on the background of the PQRST and their meaning on the EKG please read http://www.edinformatics.com/inventions_inventors/electrocardiogram.htm

EKG: A tool with remarkable clinical power

- An EKG reading can diagnose an evolving heart attack, identify life threatening arrhythmias, effects of a pulmonary embolus or blood clot in the lungs, or just a normal heart that functions and beat properly.

- Come learn with me how to read EKGs.  They are easy to read, fun to interpret and can carry BIG meaning behind their readings. 

- Do you know the heart gives off electricity and what that electricity helps with?
- Do you know what the letters PQRST mean?