Asystole: The Total Absence of a Heart Beat
Asystole is defined as the absence of cardiac electrical impulses. This means the heart's electrical system is no longer sending out signals and therefore the heart muscles are no longer contracting. This will result in no blood flow and, if not quickly corrected, death.
About the Heart
The heart is primarily regulated by hormones, nerves, and electrical impulses. The hormones and nerves normally control the heart rate. They do this by telling the heart's electrical system how slow to send electrical signals which will cause the heart muscles to contract. If the heart is left on its own, with no hormonal interference, it will beat at about 100 beats per minute. At rest, the hormones actually slow down the heart rate.
The heart's electrical system is controlled by two nerve bundles. The top one, located in the right atrium (top chamber), is called the sino-atrial node, or SA node. The lower one, located on the right ventricle (lower chamber), is called the atrio-ventricular node, or AV node. The SA node will send an electrical signal that will flow through the top chambers and cause them to contract. This signal will also be sent to the AV node which will absorb the signal and ‘hold onto it' for a split second. Then, it will release it and allow it to travel through the muscles of the lower chamber and cause them to contract. The need for this ‘holding onto' the signal is so that all chambers do not contract at the same time. If this were to happen the heart would not be able to pump blood effectively.
When this electrical system malfunctions, because of injury, a heart attack, or some other kind of heart malfunction the heart can't beat properly. Although it does not happen immediately, if the heart rhythm is not restored, the heart may suffer what is known as asystole.
Asystole sometimes follows bradycardia or tachycardia when either are severe enough and untreated.
First Aid and Treatment
As first aiders we have absolutely no way of knowing if a person is suffering from asystole. All we will know is that the casualty is not breathing, and therefore most likely will also not have a heart beat. We cannot know what is happening electrically. Therefore, all we can do is cardiopulmonary resuscitation (CPR) and call for advanced medical care. It is impossible for someone to be suffering asystole and still be conscious.
In asystole, the heart is not likely to respond to defibrillation because it is already depolarized. This means shocking the heart will not ‘reset' it, because there is nothing to ‘reset'. Again though, keep in mind that we have no way of knowing this, so we need try our best to revive the person.
Some emergency physicians do, however, advocate the trial of defibrillation in case the rhythm is actually fine ventricular fibrillation, or a rhythm that is shockable but too small to be seen on the monitor.
When asystole is confirmed by a physician, there are still treatments that may be effective in a hospital setting. These include:
- Administration of epinephrine, also known as adrenaline.
- Administration of atropine to block vagal tone that may be preventing the heart from beating.
- Surgically opening up the chest and applying a small electric shock to the heart at a regular rate in hopes of causing it to beat.
- Open heart massage. Obviously this is very invasive and only done as a very last resort in an attempt to save the person.
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