It's not a Heart Attack

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It's not a Heart Attack

Sudden cardiac arrest (SCA) is not the same as a heart attack. Often confused, the two problems have different origins, causes, and outcomes.

SCA happens when the heart abruptly and without warning starts beating very rapidly and erratically. It is a leading cause of death in the United States, responsible for half of all heart disease deaths.

SCA occurs when the heart’s electrical system malfunctions. It is not a heart attack, which is also known as a myocardial infarction (MI), although SCA can occur in association with a heart attack. A heart attack occurs when a blockage in a coronary artery (blood vessel that supplies oxygen to the heart) interrupts the flow of oxygen-rich blood to the heart, causing heart muscle to die. If the heart can be compared to a house, a heart attack occurs when there is a plumbing problem, and SCA occurs when the problem is electrical.

The most common cause of SCA is an arrhythmia called ventricular fibrillation (VF). In a healthy heart, the built-in electrical system has a “pacemaker” that triggers a normal heartbeat spreading from the top chambers (atria) to the lower chambers (ventricles) in an organized manner. This causes the heart muscle to contract and pump blood throughout the body.

In VF, the normal electrical signals become overwhelmed by rapid and chaotic electrical signals coming from the ventricles. The ventricles start to quiver (fibrillate) instead of contract, and they no longer pump blood through the body. With a lack of blood flow, the brain becomes starved of oxygen, causing the victim to lose consciousness within seconds. Unless the heart’s regular rhythm is restored by an emergency shock, using a machine called a defibrillator, death occurs within minutes. The majority of VF and SCA victims die before reaching the hospital.

	Heart Attack	Sudden Cardiac Arrest
Other Names	Myocardial Infarction (MI)	Cardiac Arrest Sudden Cardiac Death
Cause	Clogged artieries (coronary artery disease)	Electrical problem that makes two of the heart's four chambers quiver instead of contract. Arrhythmias called ventricular fibrillation (VF) and ventricular tachycardia (VT).
What Happens	Clogs block the flow of oxygen-rich blood to the heart, which may cause some heart muscle to die	Chambers stop effectively pumping blood; no oxygen-rich blood reaches the brain or body. The victim loses consciousness and dies within minutes if no treatment is provided (CPR and/or shock from a defibrillator).
Likelihood of Making it to the Hospital	People usually survive. Many victims carry medicines, such as nitroglycerin, that help prevent or limit heart attachs. Many arrive at the hospital in time to receive emergency treatment.	Unlikely. The vast majority of SCA victims die within a few minutes, often before an ambulance arrives.
Warning Signs	Usually symptoms like chest pain or pressure. They may be mild at first and become more severe.	Often no warning. Suddenly, the heart beats extremely quickly and/or irregularly.
Advance Notice	High blood pressure High cholesterol Overweight Lack of exercise	Victims often are active and appear healthy and free of heart disease. However, SCA victims typically had health problems, often coronary artery disease, and did not know it.
Emergency Treatments	Medicines Angioplasty or bypass procedures to clear blocked vessels CPR	An emergency shock to the heart using the "paddles" of a machine called a defibrillator. CPR can help to keep blood flowing until a shock is administered. Some patients who are at risk of SCA may have a defibrillator implanted in the chest, to administer an instantaneous shock in the event of a dangerous arrhythmia.