Definition of Sudden Death

An unexpected, natural, death that occurs suddenly and abruptly and usually within one hour of the onset of symptoms in an apparently well person without prior known condition that would appear fatal and where the death could not be ascribed to other causes.

Definition of Sudden Cardiac Death

The commonest cause of sudden death is due to cardiac abnormalities and hence the term“sudden cardiac death“. Sudden cardiac death is an unexpected, natural death, due to cardiac causes initiated by an abrupt loss of consciousness usually within one hour of the onset of symptoms in a person who may or may not have recognised pre-existing heart disease but in whom the time and mode of death are unexpected.

Prevalence

Sudden cardiac death is the main cause of sudden death and is responsible for more than 80% of all the causes of sudden death.

The main mechanism of the terminal event in sudden cardiac death that occurs within the first hour is usually due to a serious abnormal rhythm of the heart (arrhythmia). This rhythm is known as ventricular fibrillation and it describes the loss of function of the heart muscles resulting in failure of the heart to pump. The heart muscles quiver instead of contracting. This abnormal rhythm occurs in about 90% of patients with sudden cardiac deaths

The Magnitude of the Problem of Sudden Cardiac Death

Sudden cardiac death is responsible for about half of all deaths related to heart diseases worldwide. The most common being heart attack. It has been estimated that about half the patients who suffer heart attack will die of sudden death. In USA more than 300,000 sudden deaths per year from heart attacks.

The problem and challenge of sudden cardiac death for doctors is that there is only a small portion of potential victims who are at risk of sudden cardiac death that could be identified and this is classified into the high-risk group. However those patients who are at high-risk for sudden cardiac death represent a very small portion of the total sudden cardiac death population. The vast majority (85%) of the sudden cardiac death event occur in patients with no clear risk or minimal risk for sudden cardiac death. This pose a challenge to doctors to find ways to identify those people, not yet patients, with no obvious risk of sudden cardiac death but potentially may die suddenly.

Who is at Risk for Sudden Cardiac Death?

Special Issues of Sudden Death in the Young

Recently there has been numerous media attention on young people and competitive athletes collapsing and dying suddenly. This warrants special attention.

Sudden death in young, competitive athletes especially marathon runners and triathlons

What is known?

1. Sudden death can occur in young, competitive athletes participating in extreme sports i.e. marathon runs, triathlons or ironman. This has been documented way back in 2500 years ago.
2. Such fatalities at sporting events usually attract broad attention in the modern media because of the iconic representation of such athletes as the epitome of health and admired by many people because of their athletic prowess. Death is therefore counter intuitive in this population. And so when it occurs, it usually has a tremendous devastating impact on families, communities and physicians and attract considerable public and media attention.
3. The absolute risk is however small, but nonetheless “not inconsequential” and therefore warrants action to identify young competitive athletes that may be prone to sudden cardiac death.
4. It is usually the final 1.6 km of marathon run which represents less than 5% of the total distance and yet accounts for almost 50% of sudden cardiac deaths.
5. The final sprint with sudden cessation may also be more dangerous than generally realised.
6. Sudden cardiac death appears to be greater in triathlons than in marathon runners. The risk of sudden cardiac death in triathlons is 2 times that the risk of marathon runners. The risk of sudden cardiac death in the triathlons is usually in the swimming portion of the event.
7. The risk of sudden cardiac deaths in particular exists in short distance triathlons, i.e. those events that are filled with typical “weekend warriors”.
8. Sudden cardiac deaths events occur more frequently in the males than the females in a ratio of 9:1. The reason perhaps young women are less frequently affected is probably because of the lower overall participation rates and their absence from certain extreme sports.

The common causes of sudden cardiac deaths in young athletes differ from that in middle and older athletes.

The young athletes are defined as below the age of 35 and the older athletes include ages above 35 years old. For the young athletes below the age of 35, the commonest cause of sudden cardiac death is an inherited condition called hypertrophic cardiomyopathy (33% of deaths occurs with this condition). This is a condition where there is thickening of the muscles of the heart. The next commonest cause is a condition called coronary anamolies, i.e. the coronary arteries that supplies the heart are coming out in abnormal direction from the usual site and results in a cut-off of blood supply during extreme physical activities. This represents 14% of the causes of sudden deaths in young athletes.

Other common condition include myocarditis which is an infection of the muscle of the heart in particular especially viruses, coronary artery disease (5 – 10%), rupture of the aorta (7%), indeterminate causation of left ventricular hypertrophy (18%), i.e. muscle thickening of the heart and 3% are totally unexplainable. The most common non-cardiac sudden death is heat stroke.

In competitive athletes above 35 years old, the major causes of sudden cardiac death is usually due to coronary artery disease and is similar to that described under the heading of who is at risk of sudden cardiac death.

How Can Sudden Death Be Prevented?

There are several things that can be done to reduce the risk of developing sudden cardiac death. First, one can go through a check-list to see whether he or she is at risk of sudden cardiac death.

The check-list would include the following :

Modified 12-Element AHA Recommendations for
Preparticipation Cardiovascular Screening of Competitive Athletes

There are several things that can be done to reduce the risk of developing sudden cardiac death. First, one can go through a check-list to see whether he or she is at risk of sudden cardiac death.

The check-list would include the following :

Modified 12-Element AHA Recommendations for
Preparticipation Cardiovascular Screening of Competitive Athletes

* Exclude physical examination to be done by doctor
Based on the above check-list, if any of these are present, one should see a doctor to undergo further evaluation with a physical examination and also investigations as discussed by my colleague which may include ECG, 2D Echo/Doppler study, treadmill exercise stress test, 24-hour Holter monitoring, etc.

Treatment of Underlying Conditions that May Lead to Sudden Cardiac Death

After the clinical assessment, if the patient is found to have treatable cardiac disease, then it is obvious that this will have to be done. The most common obviously are as follows :

Coronary artery disease. Sudden cardiac death can occur during a heart attack and as mentioned, half of such patients will not arrive in hospital on time. Heart attack results in a sudden loss of the heart muscle due to damage of the muscles from the lack of blood supply by a blocked coronary artery. If found to have significant coronary artery disease, patient will require medication, PTCA/stenting or coronary artery bypass surgery to avoid the heart attack and therefore prevent the occurrence of sudden death.

Secondary prevention of coronary artery disease

Once a patient has documented coronary artery disease (chest pain which is due to angina, survived a previous heart attack, angioplasty/stenting or bypass surgery) he should be put on a series of medications that would include beta-blocker, ACE inhibitor, statins and anti-platelet agents (like Aspirin or Plavix).

Heart failure

In heart failure patients, sudden cardiac death is one of the commonest presentation. These patients have very poor heart function and the heart pump is severely weakened due to damage of the muscles of the heart. These patients should be monitored carefully and long-term medications are required. It would include all that were mentioned above as well as special medications to prevent abnormal rhythms of the heart.

Furthermore in patients with documented electrical activities (arrhythmias) that are potentially life-threatening, an ICD (implantable cardioverter defibrillator) which is a pocket-sized device that sends electrical currents to the heart to stop the fibrillation of the heart may prolong life by preventing or treating such abnormal rhythm. The ICD is about the size of a standard pager with leads (wires) put into the heart chambers and a pulse generator underneath the skin of the chest. The ICD can automatically detect abnormal rhythm of the heart which may lead to sudden cardiac death and revert the rhythm back to normal by delivering a small electrical shock to terminate the fibrillation. In addition the ICD can also function as a pacemaker if the heart beat is slow or did not recover from the shock.

Inherited muscle disorders of the heart

As mentioned previously, some of the more important inherited disorders of the heart muscles include a condition called hypertrophic cardiomyopathy which results in abnormal thickening of the muscles of the heart. These changes in the heart muscles can cause ventricular fibrillation resulting in sudden cardiac death. The diagnosis is usually made on a 12-lead ECG and a 2D Echocardiogram. When a person is diagnosed to have hypertrophic cardiomyopathy, he/she is at high risk of sudden cardiac death especially when their siblings have also died from the same condition. Once again it is usually due to abnormal rhythm of the heart, in particular ventricular fibrillation. People with this condition should avoid extreme sports and should avoid sudden strenuous physical activities which may trigger off the abnormal heart rhythm. An ICD can be implanted to prevent and treat the abnormal heart rhythm should it occur.

Electrical disorders of the heart

As mentioned before, there are numerous electrical disorders of the heart of which most of them could be detected on 12-lead ECG. The commonest being a condition called Wolff-Parkinson-White syndrome which is due to an extra electrical pathway which connects the upper to the lower chambers of the heart. This can potentially cause an electrical short circuit resulting in a rapid heart beat. This can be treated by medications or by a procedure called catheter ablation where a catheter can be advanced into the heart via a vein usually from the arm or groin to locate the site of the extra pathway and a radiofrequency wave could be delivered to burn off this abnormal pathway.

The other 2 common electrical disorders are called ion channel disorders of the heart muscles and this would include the Brugada’s syndrome and long QT interval, both of which occurs in apparently healthy individuals with no known heart problems. The diagnosis can be made on 12-lead ECG and usually symptoms of fainting spells or epileptic fits must be looked for. In such patients, an ICD would be required to prevent the sudden cardiac death syndrome.

How can sudden cardiac death be treated? – Role of Bystander CPR

The only treatment when the heart suddenly stops beating (i.e. cardiac arrest) is to perform bystander CPR. This is a stop-gap measure while awaiting for definitive treatment by the paramedical service personnel arriving in an ambulance. The bystander CPR include rapid continuous chest compression (ccc) to allow the blood to circulate to the brain as well as to the heart and to then await for a defibrillator which is the equipment that delivers an electric shock to the heart and reverting the fibrillation back to normal rhythm. This is the definitive treatment for sudden cardiac arrest and this should be done within 5 minutes from the time of a witnessed collapse.