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| Paramedic’s Corner: Atrial fibrillation, Part I |
By: Ambulance Director Gary Carmack
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Posted: Wednesday, April 15, 2009 8:49 pm
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These two EKGs show atrial fibrillation on the top and a normal sinus rhythm on the bottom. As explained in the article, the bottom readout is how your heart should look on the EKG.
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My best friend since childhood has been battling Atrial Fibrillation (a-fib). So is another friend I’ve known since teenage years, and a close relative of mine. People ask a lot of questions about a-fib, so I will attempt to describe this cardiac arrhythmia. This will most likely require two articles, possibly three, because I will need to start with some basic cardiology electrical-conduction information for the readers.
I attended paramedic school in 1976 at the University of Missouri Medical Center in Columbia. My favorite subject was always cardiology. I loved the study, however hard it was — I loved it. Perhaps it is as Carl Sagan says (from Broca’s Brain): “Understanding is a kind of ecstasy” — or maybe it’s just the good feeling when “the light comes on.” Anyway, I have studied cardiology for years and taken care of many patients in atrial fibrillation.
To understand any cardiac arrhythmia it is helpful to understand how the heart electrical conduction system normally functions. There are a group of specialized cells located in the upper–posterior wall of the right atrium. This group of cells is called the sinoatrial node, commonly called the SA node. The SA node is the normal and dominant pacemaker of the heart. In adults when all is normal, the SA node fires at a rate of 60 to 100 beats per minute. This SA node pacing is known as a sinus rhythm, and the SA node fires causing a wave of positive charges to proceed outward to stimulate both atria to contract. This is called atrial depolarization and on the electrocardiogram, this produces a wave on the paper called a “P” wave.
People often ask about the SA node, “OK, but what makes it fire, stimulates it to action?” This unique feature of our wonderful body that God created is called “automaticity.” This means self-excitation, the individual cells of the conduction system can depolarize without any impulse from an outside source. This is how the cells become stimulated — actually this is a story of positively and negatively charged ions, sodium and potassium, called the cell’s sodium-potassium pump.
The cell’s sodium-potassium pump works by expelling sodium (Na+) out of the cell, then after repolarization (a recovery period) the Na+ reenters the cell creating a charge as the potassium (K+) escapes. This creates a positive charge. This influx of sodium and a slower influx of calcium (Ca+) create action and the cells depolarize or fire. Thus, if all is normal and the SA node fires with regularity at 60 to 100 beats per minute, life is good. However, many things can cause a disturbance in the electrical conduction system causing cardiac dysrhythmia. There are many different cardiac dysrhythmia, but for this article we will move on to atrial fibrillation (a-fib), not to be confused with ventricular fibrillation (v-fib) which is deadly ... essentially is death. V-Fib is a “true” arrhythmia, the prefix “a-” meaning “without rhythm.” There is no rhythm in v-fib and the person is in full cardiac arrest. Atrial fibrillation is actually more correctly termed a “dysrhythmia,” the prefix “dys-” meaning difficulty with rhythm. That's the same prefix used in the word “dysfunctional,” and has a similar meaning.
Atrial fibrillation is a dysrhythmia, may be chronic and sustained, and is usually associated with underlying heart disease such as congestive heart disease, rheumatic heart disease, hypertension (high blood pressure), atherosclerotic heart disease, or hyperthyroidism (overactive thyroid). A-fib can also be associated with heavy alcohol ingestion, such as binge drinking (so-called holiday drinking), or chronic heavy intake.
Usually atrial fibrillation itself isn’t life-threatening, but it is a medical emergency. From the paramedic’s point of view, as far as emergency care, we are educated to determine two types. One is controlled a-fib, which means the rate is still slow enough that the heart can still fill with enough blood to pump out and maintain life. When a-fib is controlled with a slow ventricular rate it is fairly safe as far as the trip to the hospital. With that said, it should be noted that a-fib is not an arrhythmia of healthy, young individuals. It is a very irregular chaotic heart arrhythmia that is the result of a very irritable atrium. Nevertheless, if it is controlled (slow), paramedics will usually start oxygen, an IV life-line, monitor the heart with an EKG and closely observe in case the a-fib become what we call a rapid or uncontrolled a-fib with a rapid ventricular response. When this happens, the patient becomes in danger of poor perfusion because the heart can’t fill properly and provide the body with sufficient blood supply. Therefore, the person might go into heart failure. Another danger is the possibility of emboli (blood clots) developing, and the emboli can cause a stroke.
If the a-fib is rapid and uncontrolled, the paramedic will start oxygen, start an IV life-line, and then either administer an emergency medication, or if the case is serious enough, will shock the heart with a controlled shock called cardioversion. Usually we will only cardiovert if the heart rate goes above one hundred and fifty and the patient is becoming unstable.
Next week we will focus more on a-fib, the symptoms which the patient will notice, the possibility of stroke, and various treatments.
At the top of this article are two EKGs showing the readers the difference. The top EKG is atrial fibrillation. Note the totally irregular rhythm, total chaos, and absent P waves. The waves the arrow is pointing to are called F waves, for fibrillatory waves. This means there is no coordinated atrial activity and there is a loss of normal cardiac output.
Then look at the bottom rhythm. There are nice P waves, with a regular and normal sinus rhythm. The bottom one is how your heart should look on the EKG.
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