Sudden cardiac death (SCD) is a sudden, unexpected death caused by loss of heart function (sudden cardiac arrest). About 95% of people who experience a cardiac arrest die before reaching the hospital. Overall, about 1,000 cardiac arrests occur each day in the United States. SCD is responsible for half of all heart disease deaths. The cause of SCD is fatal abnormal heart rhythm called arrthymia (usually ventricular tachycardia or ventricular fibrillation).
Despite dramatic TV portrayals of patients being revived from cardiac arrest, the chances of survival in real life are slim. Most patients die instantly without much suffering. If basic and advance life support management by trained family members can be administer immediately, chances of survival is better. Onset of brain damage starts at 10 minutes after the heart stops. Therefore some patients may survive but remain in vegetative state if resuscitation was delayed.
How Is Sudden Cardiac Arrest Different from a Heart Attack?
Sudden cardiac arrest is not a heart attack (myocardial infarction) but can occur during a heart attack. In general, a cardiac arrest is much more dangerous than a heart attack.
Heart attacks occur when there is a blockage in one or more of the arteries to the heart, preventing the heart from receiving enough oxygen-rich blood. If the oxygen in the blood cannot reach the heart muscle, the heart becomes damaged.
In contrast, sudden cardiac arrest occurs when the electrical system to the heart malfunctions and suddenly becomes very fast and unproductive. The ventricles may flutter or quiver (ventricular fibrillation), the heart actually stops beating and quivers with uncoordinated contractions and blood is not delivered to the body. In the first few minutes, blood flow to the brain will be reduced so drastically that a person will lose consciousness. Death follows unless emergency treatment is begun immediately.
Emergency treatment includes cardiopulmonary resuscitation (CPR) and defibrillation. CPR is a manual technique using repetitive pressing to the chest and breathing into the person's airways that keeps enough oxygen and blood flowing to the brain until the normal heart rhythm is restored with an electric shock to the chest, called defibrillation.
What Are the Risk Factors of Sudden Cardiac Arrest?
There are many factors that can increase a person's risk of sudden cardiac arrest and sudden cardiac death, including the following:
Previous heart attack with a large area of the heart damaged
A person's risk of SCD is higher during the first six months after a heart attack.
Prior episode of sudden cardiac arrest.
Family history of sudden cardiac arrest or SCD.
Heart failure: a condition in which the heart's pumping power is weaker than normal.
Hypertrophic cardiomyopathy: a thickened heart muscle that especially affects the ventricles.
Can Sudden Cardiac Death Be Prevented?
If you have any of the above listed risk factors for SCD, it is important that you speak with your doctor about possible steps to reduce your risk.
Keeping regular follow-up appointments with your doctor, making certain lifestyle changes, taking medications as prescribed, and having interventional procedures or surgery (as recommended) are ways you can reduce your risk.
To prevent future episodes of sudden cardiac arrest, your doctor will want to perform diagnostic tests to determine what caused the cardiac event. Tests may include electrocardiogram (ECG or EKG), ambulatory Holter monitoring, echocardiogram, cardiac catheterization and electrophysiology studies.
Medications: To help reduce the risk of sudden cardiac arrest, doctors may prescribe medications to people who have had heart attacks or who have heart failure or arrhythmias such as irregular heart rhythms. These medications may include ACE inhibitors, beta blockers, calcium channel blockers, and other antiarrhythmics. For patients with high cholesterol and coronary artery disease, statin medications may be prescribed. Many good quality researches have shown that beta blockers reduce the risk of SCD.
For patients with coronary artery disease, an angiogram and interventional procedure such as angioplasty (blood vessel repair) or bypass surgery may be needed to improve blood flow to the hibernating or ischemic heart muscle. This should be performed first before considering ICD.
Implantable cardioverter-defibrillator (ICD) is indicated for people whose risk factors put them at great risk for sudden cardiac death, an ICD may be inserted as a preventive treatment. An ICD is a small machine similar to a pacemaker that is designed to correct arrhythmias. It constantly monitors the heart rhythm and treats dangerous arrthymia. When it detects a very fast or slow heart rhythm, it delivers energy (a small, but powerful shock) to the heart muscle to cause the heart to beat in a normal rhythm again.
The ICD may be used in patients who have survived sudden cardiac arrest and need their heart rhythms constantly monitored. It may also be combined with a pacemaker to treat other underlying irregular heart rhythms or heart failure.
Educate your family members: If you are at risk for SCD, talk to your family members so they understand your condition and the importance of seeking immediate care in the event of an emergency. Family members and friends of those at risk for SCD should know how to perform CPR.
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