Thursday March 22 2012
Heart collapses like Fabrice Muamba's are serious
The mid-game collapse of footballer Fabrice Muamba has received massive press attention this week, as the 23-year-old was left in a critical condition after his heart stopped beating. The Bolton Wanderers midfielder collapsed during an FA Cup tie against Tottenham and needed urgent medical attention to restart his heart.
Since his collapse on Saturday, Muamba has been treated at the London Chest Hospital, where his condition has improved. He has now regained consciousness and is reported to be comfortable, although medics are still monitoring his health. The exact cause of Muamba's cardiac arrest has not been revealed.
A great deal of newspaper coverage has centred on the potential risk of serious hidden heart problems among young people. However, these types of collapses and conditions are not common and the public’s awareness of them is often higher when they occur in a high-profile setting, such as during televised sport.
What is a cardiac arrest?
A cardiac arrest occurs when the heart suddenly stops pumping blood around the body. The immediate cause of this is usually an abnormal heart rhythm, called ventricular fibrillation. This occurs when the electrical activity of the heart becomes so chaotic that the heart stops its normal rhythmic beating and quivers instead. Someone who has a cardiac arrest loses consciousness almost at once, and it is vital that their heart is restarted as soon as possible to ensure they survive. This will often require the use of an electronic device called a defibrillator to shock the heart back into normal beating.
A cardiac arrest is not the same as a heart attack, which occurs if the flow of oxygen-rich blood to a section of heart muscle suddenly becomes blocked. If blood flow isn't restored quickly, the section of heart muscle begins to die. A heart attack usually happens because of coronary heart disease.
A cardiac arrest may also be caused by the loss of large amounts of blood or fluid, lack of oxygen, the body being very hot or cold, and a blood clot in the lungs or arteries. A heart attack can lead to cardiac arrest in some cases.
What is cardiopulmonary resuscitation?
A sudden stoppage of the heart can cause permanent damage to other organs and it is vital that blood flow is restored quickly. Cardiopulmonary resuscitation (CPR) is an essential technique that is used to prevent permanent damage or even death. In CPR, the heart is pumped by external cardiac massage to keep the circulation going. CPR may also involve rescue breathing, where the lungs are inflated using mouth-to-mouth resuscitation, often referred to as the “kiss of life”.
Cardiac arrest can sometimes be corrected by giving an electric shock through the chest wall using a defibrillator. Defibrillators are increasingly found in public places, including sports grounds, although they should only be used by people who are trained to use them.
What could have caused Muamba’s cardiac arrest?
There are many different causes of cardiac arrest in young people. It has not been revealed what caused Muamba to collapse, but there has been much speculation in the press about possible causes. Most cardiac arrests in young people stem from either genetic abnormalities in the heart muscle (cardiomyopathies) or abnormalities of the heart’s electrical activity. Some of the conditions discussed in recent news include:
- Hypertrophic cardiomyopathy (HCM, also known as hypertrophic obstructive cardiomyopathy). This is the most common cause of cardiac arrest in young people. In HCM, the heart muscle becomes excessively thick, which makes the heart vulnerable to abnormal heart rhythms (including ventricular fibrillation). This is a genetic, inherited abnormality but can be made worse by prolonged athletic training, which causes the heart muscle to thicken, similar to the way exercise causes the muscles in our limbs to increase in size.
- Arrhythmogenic right ventricular cardiomyopathy (ARVC, also called right ventricular dysplasia). This is another common cause of cardiac arrest in young people. It often runs in families and happens when some of the heart muscle (in the right ventricle) is replaced by fibrous tissue and fat.
- Ion channelopathies, a range of rare genetic disorders. These cause abnormalities in the microscopic channels within the cells of the heart, which regulate the flow of sodium, potassium and calcium into and out of the cells. These chemicals are important in the way the heart generates electricity to power its beating. If these channels do not work properly, the electrical currents in the heart muscle cells are disturbed, which can lead to abnormal heart rhythms. One of the highest-profile ion channelopathies is called Long QT Syndrome.
In middle-aged and older adults, cardiac arrest and sudden cardiac death is usually caused by coronary artery disease, in which the small blood vessels that supply the heart become narrowed by a build-up of fatty material and may suddenly block.
Are these conditions common?
The defects that can cause cardiac arrest in young people are not common. For instance, in the UK it is estimated that 10,000 people have hypertrophic cardiomyopathy.
However, according to the charity Cardiac Risk in the Young (CRY), each week at least 12 people under the age of 35 die suddenly in the UK from undiagnosed heart conditions, although it believes this may be an underestimate of the extent of sudden cardiac deaths. CRY says that many of those who die are involved in sport which, while it does not cause the problem, can exacerbate existing undiagnosed heart conditions.
What about screening?
There has also been much debate in the papers about whether medical checks for these conditions in people at risk are adequate. Screening for cardiac conditions may include an electrocardiogram (ECG), which looks at the electrical conduction pathways around the heart, and an echocardiogram, an ultrasound scan of the structure of the heart. Screening techniques will detect some but not all of the conditions that can cause cardiac arrest, and even repeated screenings may not detect some heart problems. While most elite athletes will be regularly screened, the European Society of Cardiology and the International Olympic Committee recommend cardiac screening for any young person taking part in competitive sport.
Because the conditions that cause cardiac arrest in young people can be inherited, relatives of anyone who has died suddenly after a cardiac arrest should be evaluated for signs of any relevant heart condition, as they could be at risk of similar events.
What should I do if someone has a cardiac arrest?
If someone is not breathing normally and is not moving or responding to you after an accident, call 999 for an ambulance. Then, if you can, start performing CPR straight away. CPR can keep blood and oxygen circulating in the body. If you can do CPR, it may buy the vital time needed for professional help to arrive. Find out more about CPR.
The British Heart Foundation and other organisations run courses that teach important emergency life-support techniques. Read more information on the British Heart Foundation website.