Me Again

• by SMITTY
• 2007-11-15 01:11:27
• General Posting
• 1342 views
• 2 comments

Hello Folks,

Well my trip got delayed a couple of days because I had a flair up of my arrhythmia on Tuesday morning and had to go to the doctor. I got some new medicine and I was instructed to wait until tomorrow or the next day to see if things settle down a little before we leave. So, I'll see if I can give some of you good people something to read.

Some questions I saw today were "How does a sick SA node normally respond to the use of a pacemaker? Does it become lazy, does it recover somewhat due to the load being carried by the PM or does the introduction of a PM have no influence on the node’s behavior?"

As I understand the way a pacemaker works, the sinus node will not even notice the pacemaker. However, the pacemaker will definitely notice the sick sinus node. As you know I'm sure, the sinus node is the location of our heart's natural pacemaker and a manmade pacemaker does nothing until it checks to see if the sinus node is sending an impulse to make the heart beat. If the pacemaker does not see any indication of an impulse from the heart's own pacemaker, then it will send an impulse to make the heart beat. The pacemaker follows this procedure every time your heart beats. I have seen some say that having a pacemaker can make the sinus node get lazy or weaker, but that cannot be true because again the pacemaker does nothing unless it sees a failure to by the heart’s natural pacemaker to make our heart beat. If my theory is correct, then if your heart's sinus node has any recuperative ability it will recuperate and as it returns to the job of making your heart beat the manmade PM gets to sit there doing nothing more often. However, that manmade job will continue to monitor every heart bat to see if it needs to send an impulse.

While I'm on this subject, I recall seeing where someone asked something about what it means to have a pacemaker that works 100% of the time. All pacemakers work 100% of the time. However, that does not mean they are necessarily sending an impulse to make your heart beat 100% of the time. A pacemaker is our heart’s helper not a replacement for anything. Now I know some people's heart for various reasons must have an impulse from the manmade pacemaker to beat, however, even those pacemakers will be checking your heart's PM every time before it sends an impulse. What I'm saying is when someone says your pacemaker is working X% of the time, they should define that a little further.

My PM has a low setting of 70 and a high of 110. Since my normal rate is about 55 to 65, my PM does work most of the time, except when I do something to kick my heart rate up to somewhere above 70. Then the PM just monitors my heart but does nothing to help it beat until it finds my natural PM is failing to send an impulse.

While I'm sitting here, I'll mention something about ejection fractions that I learned yesterday. I've been going to the same heart clinic since 2000. I've had many tests where they determine my EF. I’ve been told I had an EF as low as 37% and as high as the low fifties. Just in case someone is not familiar with exactly what an ejection fraction is, it is an estimate of the amount of blood that is pumped by to our body each time the ventricle contracts. As I understand, a normal heart has about 200 cc of blood to be pumped out each beat, but that normal heart will pump only about 60% of that blood. This means with each beat a normal heart pumps about 120 cc of blood. Now if a person has a 40% EF that means that heart will pump only 80 cc of blood each beat. As anyone can imagine, the lower the amount of blood pumped each beat the more likely that person to get SOB or more tired than someone with an EF of 60%.

Back to my original reason for starting this subject. I was diagnosed with congestive heart failure in the mid-80s and I have known that my EF would be going down as the years go by. I asked for an explanation on how could my EF bounce around since I was certain my heart muscle was getting a little weaker each year. The answer I got was my EF would not increase and the variance in the figures was due to the person interpreting the test results and some are more conservative with their findings than others. It seems that most doctors have a fudge factor, based on their overall knowledge of a patient and their illness, they can apply to the numbers they are given and that number is what the patient is usually given.
I need to add one thing about EF and the amount of blood pumped by a healthy heart. You athletes, especially you runners, that have caused your heart increase due to all you exercising, your EF may be as much as 70%, or more. Also, with your larger heart, the amount of blood available to be pumped can be much more than 200 cc.

Have a good day everyone and if I'm lucky I'll see you down the road.

Smitty