Sudden Cardiac Arrest and Sudden Cardiac Death - Are They The Same?

What is Sudden Cardiac Death?

Sudden Cardiac Death refers to sudden, unexpected death caused by sudden cardiac arrest. It is estimated to be responsible for all deaths caused by heart disease.

Sudden Cardiac Arrest occurs when the electrical system of the heart malfunctions and becomes highly irregular. This in turn causes the heart to beat dangerously fast. Subsequently, ventricular fibrillation might occur with the end result being blood not being delivered to the body. Reduced blood flow to the brain will result in unconsciousness and emergency treatment is required.

Heart attacks, as the term is used in a traditional sense, refers to the situation where heart tissue fails to receive sufficient nutrients and blood flow due to blockages to one or more of the arteries supplying the heart, resulting in eventual cardiac tissue damage. With sufficient cardiac tissue damage, the electrical system of the heart will malfunction and that eventually leads to cardiac arrest.

Cardiopulmonary Resuscitation (CPR) and electrical defibrillation remain the mainstay of Emergency treatments for cardiac arrests.

CPR is a manual technique using repetitive chest compressions and manual assisted breathing to maintain sufficient oxygen and blood flow to the brain until a normal heart rhythm is restored. Defibrillation refers to the deliverance of an electrical current as an electric shock to the heart in an effort to reset the electrical rhythms therein and restore normal heart rhythm.

What Are the Symptoms of Sudden Cardiac Arrest?

Symptoms vary and can include:

• A racing heart beat
• Unexplained dizziness and giddiness
• Chest pain

Sometimes, cardiac arrest can occur without prior symptoms.

What Causes Sudden Cardiac Death?

Sudden Cardiac Death are caused by abnormal heart rhythms called arrhythmias, the most life threatening of which is ventricular fibrillation - an erratic and disorganized firing of impulses within the ventricles of the heart. If left untreated, ventricular fibrillation can cause brain death within minutes.

What Are the Risk Factors of Sudden Cardiac Arrest?

Risk factors include:

• History of previous cardiac events, especially if significant cardiac tissue damage has occurred.
• 6 months after an initial heart attack
• Coronary Artery disease
• Smoking
• Hypertension
• High cholesterol levels
• Family history of heart disease
• A cardiac Ejection fraction of <40%
• Congenital heart defects
• Recurrent syncope and fainting
• Heart Failure

• Hypertrophic cardiomyopathy - a condition where heart muscle is thickened without proper electrical connectivity
• Biochemical abnormalities, such as fluctuations in potassium and magnesium levels from use of other drugs (eg diuretics like Frusemide)
• Obesity
• Diabetes Type II
• Recreational drug use

Can Sudden Cardiac Death Be Prevented?

The following steps are recommended:

• Speak with your Doctor if you have any known risk factors and have a full medical assessment.
• Perform the necessary diagnostic tests such as a simple bedside electrocardiogram (ECG) or transthoracic echocardiogram.
• Determine your ejection fraction.

Ejection Fraction (EF): EF is a measurement of the percentage (fraction) of blood pumped (ejected) out of the heart with each beat.

It is usually measured during a transthoracic ultrasound echocardiogram and usually ranges from 55% - 75%.

An EF <40% predisposes a patient to sudden cardiac arrests.

• Lifestyle changes. These include quitting smoking, losing weight, exercising regularly, low fat diets etc.
• Control diabetes, hypertension and cholesterol levels.
• Medications as prescribed by your doctor.
• In certain situations where abnormal cardiac rhythms occur sporadically, and implantable cardioverter-defibrillator (ICD) can be inserted.

An ICD is a small machine similar to a pacemaker designed to correct arrhythmias once detected. It constantly monitors the heart rhythm and detects abnormal cardiac rhythms and records them. When it detects abnormal cardiac rhythms, it delivers a small electrical shock to cardiac tissue to reset the heart back to its normal rhythm. These events are then recorded and can be viewed by the attending doctors at a later date for further analysis and adjustment of the ICD.

ICDs are used for survivors of sudden cardiac arrests and for patients who require constant monitoring of their hearts due to existing conditions causing abnormal heart rhythms.

• Interventional Surgery such as angioplasty for patients with coronary artery disease or bypass surgery can be performed to reduce the risk of SCDs. For patients with congenital abnormalities or cardiomyopathies, surgical intervention will likely be needed to correct any underlying abnormal cardiac rhythms.
• Other non-invasive procedures like cardioversion electrically or catheter ablation techniques can also be used.
• Socially, speaking with family members who are at risk of SCD is the first step to preventing the occurrence of SCDs.

Can Sudden Cardiac Arrest Be Treated?

Cardiac arrests require immediate action. If CPR and defibrillation is performed adequately during the initial few minutes of onset, survival is estimated to be as high as 90%.

What Should I Do if I Witness Sudden Cardiac Arrest?

• Call the emergency helpline and activate an ambulance immediately.
• Perform CPR if you are trained.
• Use a defibrillator if available and you are trained.
• Post CPR, have patient transferred to hospital at the earliest possible time.

Sudden Cardiac Death and Athletes

Do be aware that cardiac death can also occur in athletes. The usual scenario being that of runners participating in social marathons and collapsing in the process.

Hence, do not take the risk. See your doctor for the relevant investigations.

About The Author

Dr Lau Tzun Hon is a resident housecall doctor at CMY Medical. He received his MBBS (Hons) from Sydney University in 2001 and has served in the both private and government restructured hospitals prior to commencing his practice in Home Care.

While in the Government Restructured Hospitals, Dr Lau served primarily in the Department of Accident & Emergency Medicine and Anaesthesia. Upon entering the Private sector, Dr Lau worked in both public and private A&E departments before venturing into Home Care.

Over the years, he has developed a strong passion to maintain and  enhance the quality of life for patients under his care.  A strong believer that healthcare does not need to be financially straining, Dr Lau often delivers more value beyond expectations.

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