Heart disease is the leading cause of death in the United States. Most of us think of a heart attack when we hear of heart disease but this is only one type of heart disease. Heart attacks damage the heart muscle and weakens the heart but most heart attacks do not cause the heart to stop. When the heart stops it is referred to as sudden cardiac arrest (SCA). Most cases will lead to death within minutes if there is no medical care.
What happens when the heart stops?
To understand what happens when the heart stops, it is first important to understand the function of the heart. After all, when the heart stops its function ceases. The heart is a hollow organ that is made up of four chambers – right atrium, right ventricle, left atrium and left ventricle. Large blood vessels lead to and away from these chambers. Valves control blood flow between chambers and between the chambers and the large blood vessels.
The heart is a pump that receives low oxygen blood from the rest of the body (in the right atrium) and pushes this blood to the lungs (from the right ventricle). The blood is then oxygenated by the lungs and carbon dioxide is expelled. Then the blood returns to the heart (in the left atrium). From here, the oxygen-rich blood is pumped to the rest of the body (from the left ventricle). Therefore the heart is responsible for ensuring that there is sufficient oxygen available for all the cells in the body but blood also carries nutrients and other essential substances.
How does a stopped heart lead to death?
Oxygen is essential for life. Cells use it along with nutrients like glucose to produce energy. This energy maintains all the essential processes that keep us alive. As a result, when the heart stops then there is insufficient oxygen for the cells to continue with normal metabolic functions. Cells die and within minutes this leads to death. The brain tissue is the most oxygen-sensitive. Once the brain is affected to a sufficient degree, death is inevitable.
Read more on sudden cardiac death.
Causes of a Stopped Heart
The heart’s pumping activity is made possible with the electrical impulses that causes the heart muscle to contract and relax. These electrical impulses are generated in the heart’s pacemaker which is known as the sinoatrial (SA) node. It passes the electrical impulses across the conduction system in the heart. This electrical activity keeps the heart beating in a rhythmic manner.
For the heart to stop, this rhythmic beating is disrupted in some way. An irregular heartbeat is known as an arrhythmia. It is the main cause of sudden cardiac arrest (stopped heart). Since the heart can generate its own nerve impulses and spread it across the heart muscle, an arrhythmia is usually due to damage or disturbance of the sinoatrial (SA) node or conduction system. When this irregularity is severe, the heart can stop altogether.
Therefore it is important to look at the causes of arrhythmias and specifically the more serious causes of arrhythmias that can lead to sudden cardiac arrest. This includes:
- Cardiomyopathy (enlarged heart)
- Congenital heart disease (heart defects present from birth)
- Coronary artery disease (narrowed heart artery)
- Conduction system problems (disturbances in the generation and/or transmission of electrical impulses)
- Heart attack
- Heart valve disease
Read more on irregular heart rate.
How Long Before Death Occurs?
Once the heart stops, there is no further distribution of oxygen-rich blood. Any remaining oxygen in the body is used up by cells. Death is not determined solely by cessation of a heart beat. Stopping of breathing and brain function are other factors that need to be considered.
Brain cells will die in approximately 4 to 6 minutes without any circulating blood carrying oxygen to it. If there is no restoration of heart function and reoxygenation of blood within 10 minutes, death will very likely occur thereafter. This time span may be altered to a limited degree by very low environmental temperatures.
It is also important to understand that even if the heart starts pumping and oxygen is being distributed again within minutes, there is still a possibility of some degree of brain damage. A person may therefore not survive without the assistance of ventilators, depending on which part of the brain is affected.
First Aid Treatment
Immediate treatment is required when the heart stops as death will ensue within minutes. CPR (cardiopulmonary resuscitation) is the first aid treatment of choice as it will ensure that oxygen can reach the vital organs to maintain life. CPR must be continued until emergency medical care is available. It is important to note that CPR can save lives in the event of the heart stopping, even if a person does not know how to perform these techniques.
The sequence for CPR used to be Airway, Breathing and chest Compression (ABC) but this has now changed to CAB. In other words, perform chest compressions first. Ensure that emergency medical services are summoned before starting CPR when alone. Alternatively, start CPR and ask another person to contact emergency medical services. With children, CPR should be done for two minutes before calling emergency medical services if alone.
It is important for every person to know how to conduct CPR. However, basic CPR techniques can be conducted even by a person who is not trained. In the event of no CPR training, focus only on chest compressions. Ideally the unconscious person whose heart has stopped should be placed on a flat hard surface like the floor.
- Place the heel of one hand on the center of the person’s chest.
- Use the other hand to cover the hand on the chest. Only one hand may be necessary for children.
- Lock the elbows in a straight position.
- Use the body weight to push down on the chest.
- Compressions should be hard and fast, maintaining a rate of about 100 to 120 compressions per minute.
Airway and Breathing
The other two important steps in CPR involves Airway and Breathing, which needs to be done after every 30 Compressions. Tilting the head backwards and lifting the chin helps to open the airway. It is important to check if the person is breathing on their own. If so, then the next step is not necessary.
The nostrils should be pinched and a rescue breath should be given. A rescue breath involves mouth-to-mouth contact where air is then blown with force. This should be done for one second and if done properly the chest should rise. Repeat for a second a rescue breath. The continue chest compression for another 30 compressions.