Dear Ashley, Ashleigh, Danielle, Kim and Heather:
Oops! I guess I got carried away with the big words. Let me try to explain the "QRS Absent" question once again.
First of all, you need to know that the heart has four chambers. The top two chambers are the Left & Right Atria (singular = Atrium). The bottom two chambers are the Left and Right Ventricles. The heart beat is started by a tiny electrical event that is created by the SA (sino atrial) Node. The SA Node is located near the top of the Right Atrium. When the heart beats, it beats from top to bottom. The electrical event that was started in the SA Node travels down the muscle in the Right Atrium and over to the muscle of the Left Atrium and, kind of like dominos falling, continues down to the Right and Left Ventricles.
There is an area of very special tissue that is located between the top and bottom chambers, called the AV (atrio ventricular) Node. The AV Node is there to *slow down* the electrical signal before it can go down to the ventricles. When the AV Node does it job the way it is supposed to, the heart beats normally. If the AV Node is sick, the electric signal from the Right Atrium can be slowed way too much and, sometimes, even completely blocked. When this happens the person is said to have "Heart Block." This is like trying to knock over all the dominoes, but when the domino that is supposed to start the lower bunch falling reaches one that has been placed a little too far away the dominoes stop falling.
Because all of this electrical stuff is going on inside the heart, we can measure the electricity with something called an electrocardiogram, ECG for short. The ECG machine looks at the electrical signals that are going on inside the heart and allows us to record the signals on paper. To make it simple to describe what we are seeing on the ECG, we have devised a "lettering" system to identify the parts of the ECG. When the top chambers are contracting (having a heart beat), the ECG prints something called a "P" wave. When the ventricles are contracting, the ECG prints out the "QRS" wave. When the ventricles are relaxing (this happens after every heart beat), the ECG prints out what we call the "T" wave. If you know how to check your own pulse, you can feel every time the ventricles contract. You cannot feel the atria contract because they are only used to push blood into the ventricles.
O.K., why is the QRS absent? In a person who has "heart block," not every beat (electric signal) can get past the road block caused by the sick AV Node (the domino that doesn't fall every time). No electric signal, no QRS. I am sorry that this stuff is so complicated, but I did not invent the system (but I'd like to find out who did!) ;-). Please let me know if I have done a little better job explaining why the QRS is absent. If it is still too difficult, please try to tell me specifically what is confusing and I will try to break it apart one little piece at a time.
I really love the pictures on the web pages. It makes me feel as if I am sitting in a circle of my curious friends answering their questions. Keep 'em coming!
Big Warm South Florida Hugs
DJ
Delos Johnson
D,
The kids really didn't have enough time to write to you today because we had so much fun with the dominoes and making them fall down - first stopping at the AV node and then falling all the way. Next week I'll talk to them about the 'QRS absent' that still needs explaining. I only got to the top part of your message today. Gosh a half hour goes by quickly.
Patti
Dear Mr. Delos,
Hi!! How are you ? No huh this time. Guess What I don't need a pacemaker. I checked. We did dominoes. My heart worked perfectly. Thanks for making this stuff easier. I still don't know the answer. It took up so much time to do this that I only get 5 minutes to write. I know the chambers now thanks for telling me. Well, I have to go.
Sincerely,
Ashleigh
PS -Please write back
Hi!! Guess what? I need a pacemaker. We did Dominnoes. And my didn't work too well.. Thanks for making that stuff clearer. Well, got to go.
Your Key PaL,
Heather
Dear Mr. D,
Thanks for clearing up your letter. Mrs.Weeg and I made a heart with dominoes around it. It looked just like your diagram. It helped me understand. Write back soon!
Your Friend,
Danielle
Dear Mr. D,
Hello!!! I have something great to tell you!!! Mrs. Weeg and I have come up with a way to make a model of how to test the heart with dominos. It's fun! We take the dominos and put them on a piece of paper with a drawing of the heart in it. Put the dominos on the piece of paper and then knock them down!!!! If something is wrong you need a pacemaker!!!!!!!!!!!!!!!!!!
your key pal,
ashley
Dear Mr Johnson,
Mrs. Weeg let us use Dominoes to understand how our hearts work. We all need Pacemakers to help our Dominoe hearts work. I think it was fun to use the Dominoes. Ashley Adkins kept accidentally knocking hers down before. She almost gave up, but Mrs. Weeg wouldn't let her.
Your friend,
Kim
