Who is What

-

Learning Objectives:

1) To apply the knowledge of the conduction system

2) To differentiate and identify the different pacemakers as reflected in the ECG

 

Who is responsible for this rhythm?

Now that you have gone through the conduction system and the Normal ECG, lets build and expand on that understanding. As have been emphasized, a Sinus Rhythm is initiated by the SA node and reflected in the ECG by a P wave. However, you would want to differentiate between positive deflection P wave, negative deflection P wave and rhythms with absence of P wave.

 

Positive Deflection P wave




In this rhythm, all the P waves are upright. Hence it is the SA node who is responsible for the Sinus Rhythm.

 


Negative deflection P waves


In this rhythm, all the P waves all negatively deflected and the QRS width are normal . Hence it is the Bundle of His who is responsible for this rhythm. It is call a Junctional rhythm. In addition, a normal QRS width, with either an absence of P waves or biphasic P waves are also characteristics of a Junctional rhythm

 


Absence of P waves with QRS width less than 0.12 seconds

In this rhythm all the p waves are absent. The QRS width is less than 0.12 seconds (less than 3 small squares. Hence it is the Bundle of His who is responsible in initiating this rhythm. This rhythm is called a Junctional Rhythm.


 

Absence of P waves with QRS width more than 0.12 seconds



In this rhythm, all the P waves are absent. The QRS width is more than 0.12 seconds (more than 3 small squares). Hence it is the Purkinjie fibres who is responsible in initiating this rhythm. This rhythm is call a Ventricular rhythm.



In Summary


Comments

Post a Comment

Popular posts from this blog

Conduction System

-
Image
Learning Objectives 1) Describe the conduction system 2) Describe the basic function of the 3 pacemakers 3) Relate the pacemakers to the tracing on an ECG Overview The cardiac conduction system is a group of specialized cardiac muscle cells in the walls of the heart that send signals to the heart muscle causing it to contract. The main components of the cardiac conduction system are the SA node, AV node, bundle of His, bundle branches, and Purkinje fibers. The SA node (anatomical pacemaker) starts the sequence by causing the atrial muscles to contract. From there, the signal travels to the AV node, through the bundle of His, down the bundle branches, and through the Purkinje fibers, causing the ventricles to contract. This signal creates an electrical current that can be seen on a graph called an Electrocardiogram (EKG or ECG). Doctors use an EKG to monitor the cardiac conduction system's electrical activity in the heart. The Sino-Atrial Node Figure 1 (SA) (Figure 1) is an oval sha...
Read more

Calculating the Heart Rate

-
Image
Learning Objectives:   1. Calculate the heart rate using the Box Method and Division Method   Calculating the rate in an ECG is an important as identifying the rhythm itself as it bears implication to the treatment. Although various methods are available, for simplicity and practicality only 2 methods will be introduced here.   The Box Method 1. Find a R wave that lands on a heavy line 2. Place the following value on succeeding heavy line as done in the diagram below 3. If the next R wave falls on a heavy line assigned the appropriate rate value to it. 4. If however the next R wave falls between 2 heavy lines, take the difference between the 2 value and divide by 5. Each of the small square is then worth that quotient.   The Division Method 1) Count the number of large boxes between 2 R waves 2) Divide that number by 300, and assign that as the approximate rate.
Read more

The 11-STEP Method

-
Image
THE 11 STEP METHOD 1. Other 2. Evaluate the P wave 3. Determine the rhythm 4. Determine the rate 5. Calculate the duration of the PR interval 6. Calculate the duration of the QRS complex 7. Evaluate the T wave 8. Calculate the duration of the QT interval 9.  Assess the ST segment 10. Interpretation 11. Treatment     THE 11 STEPS 1. Other Identify anything you consider unusual or obvious about the rhythm, e.g., extra P waves, inverted T waves. 2. Evaluate the P Wave           Are P waves present?           Do the P waves have a normal configuration?           Do all the P waves have a similar size and shape?           Is the P wave consistently followed by a QRS complex?          Is there a QRS after every P wave? 3. Determine the Rhythm You can use the pencil and paper method or the calipers method to assess whe...
Read more