Heart Attack and Sudden Cardiac Arrest

Heart attack and sudden cardiac arrest are two related but separate conditions of the same muscle of the body often mistakenly used interchangeably. Even though they are both cardiac related, prevention and treatment for each is different. Understanding the differences between the two most common and deadly heart conditions, and knowing how to recognize the signs and symptoms of each could mean the difference between life and death for the victim.

Physiology of a Heart Attack

A heart attack, also known as a myocardial infarction, is a sudden and complete blockage of one or more arteries which supply oxygen-rich blood to the heart. This kind of blockage is common in many forms of heart disease. One example is a condition known as atherosclerosis, which is clinically defined as “hardening of the arteries”. When arteries harden, “plaque” forms on the walls of the artery and ultimately blocks the artery completely. It can be thought of as a “plumbing problem”.

As more arteries become clogged completely, the circulatory system is unable to supply the heart with enough oxygen and the muscles within the heart begin to die. This condition, when it reaches its end-stage form, will generally result in a patient suffering a heart attack.   

Physiology of Sudden Cardiac Arrest

Conversely, sudden cardiac arrest (SCA), can be described as an “electrical problem.” It is a direct result of a lethal cardiac arrhythmia, generally ventricular fibrillation, which can occur in any person, at any time, regardless of health condition. Ventricular fibrillation is a rhythm defect in the heart, caused by an interruption of the natural electrical impulses produced by the sinoatrial node. The sinoatrial node acts as the heart’s natural pacemaker.

The lower chambers of the heart, known as ventricles, begin to beat in an irregular and often rapid pattern, which prevents the heart from pushing blood throughout the body. Without oxygenated blood flowing to the brain, heart and other vital organs, immediate clinical death occurs.

It is crucial to understand sudden cardiac arrest is not a condition which can be prevented entirely by lifestyle changes.  While exercise and a healthy diet help curb artery blockages, other causes of SCA include:

• An undiagnosed genetic condition such as Wolff Parkinson White Syndrome or Brugada Syndrome
• Choking
• Drowning
• Electrocution
• Excessive physical activity.

Symptoms of a Heart Attack

A heart attack has classic signs and symptoms a bystander can easily learn to recognize. Generally, someone in the midst of a heart attack will be alert, awake and able to tell you about these symptoms:

• Chest pain which can feel like intense burning or tightness (“clenched fist” feeling). This pain may radiate to the neck, between the shoulder blades, jaw, left arm, or the upper abdominal area.
• Occasionally nausea, clammy skin, fatigue, cold sweats, lightheadedness, and dizziness are present.
• Shortness of breath.
• Other symptoms, such as anxiety and a sense of impending doom, have been reported.
• Women sometimes report a stiff or painful jaw; this does not seem to be as prevalent in men.

Symptoms of Sudden Cardiac Arrest (SCA)

A person experiencing sudden cardiac arrest will not exhibit most of the symptoms present in a heart attack. SCA events truly are sudden, as the name implies. While heart attack symptoms can be gradual, sometimes occurring over days or even weeks, SCA occurs instantly when the heart goes into fibrillation and can no longer effectively pump blood. The signs and symptoms of sudden cardiac arrest include the following:

• Sudden loss of any and all responsiveness, which is defined as “no response to tapping on the shoulders or responding when asked if he/she is okay.”
• No pulse
• Not breathing (chest rising and falling). A victim may exhibit what is referred to as ‘agonal’ breathing – described as desperate gasping.  
• Some patients have reported a very brief sensation of nausea, irregular heartbeat, or rapid heartbeat prior to unconsciousness. The length of time between the patient feeling these sensations and becoming unconscious is so brief, it is immeasurable.

Treatment Options

Identifying which condition is occurring dictates which treatment needs to be administered.

Responding to a Heart Attack

Bystander Treatment of a Heart Attack

If you’re a bystander and you see someone experiencing heart attack symptoms, do the following:

• Call 911! It is not recommended you drive the person to the emergency room as this could actually delay treatment while you fill out forms and wait to get the person in to be seen.
• Stay close.  It is important to keep an eye on the person in case the heart attack turns to sudden cardiac arrest.  
• If the person has been prescribed nitroglycerin in the past, and it is close at hand, administer a dose.  
• If they have not been prescribed nitroglycerin, and you know for a fact they have no allergies or are taking medications which may interact badly with it, you can give regular aspirin.
  • Why: Since the arteries may be blocked, but not be completely closed, a blood thinner like aspirin can help blood continue to flow. The longer the heart is deprived of oxygen, the more damage is done. Thinning the blood as soon as possible will allow the heart to regain oxygenation much sooner than a patient who does not receive treatment until EMS arrives.
• Keep the patient comfortable and calm until EMS arrives.

Professional Treatment of a Heart Attack

• When professional responders arrive on the scene they will generally start an intravenous line to administer another blood thinner, such as heparin, which works via a different mechanism. They will also assess the patient and transport to the hospital if necessary.
• In the hospital, the patient will be assessed and will most likely undergo angioplasty to find and open any blocked arteries. Clot-busting drugs may also be given if the patient arrives at the hospital soon enough.
• Out-of-hospital, long-term treatments may include:
  • Medicines such as ACE inhibitors, anti-clotting, anticoagulants, beta blockers and statin drugs  
  • Additional medical procedures such as bypass surgeries to prevent further heart attacks
  • Lifestyle change recommendations including diet, safe exercise, stress management, limiting alcohol intake and quitting smoking (if relevant)
  • Cardiac rehabilitation, including education on heart disease, counseling, and training of the patient and loved ones on possible future signs and symptoms of possible future heart attacks.  
    

Responding to Sudden Cardiac Arrest

Bystander Treatment of Sudden Cardiac Arrest

If you’re a bystander and observe someone experiencing SCA symptoms, immediately begin the Chain of Survival:

• Call 911 or have another bystander call 911
• Get an AED or send another bystander to get the AED
• Begin CPR
• Turn on the AED when it arrives and follow its directions
• For every minute defibrillation is delayed, the patient’s chances of survival decrease by 10%.
• Continual CPR and defibrillation should be continued until EMS transport arrives at the scene, or until the patient regains consciousness.
• The AED should be left attached to the patient until EMS arrives for use as a monitoring tool.

It is important to remember a patient in SCA is clinically dead. There is nothing you can do treatment-wise with an AED or with chest compressions which will result in any further damage to this individual. In fact, only positive outcomes can be achieved from this form of treatment. Use of an AED and CPR should be initiated in 100% of cases, as quickly as possible.

Professional Treatment of Sudden Cardiac Arrest

• In Hospital: post-arrest care usually includes most of the treatments above for heart attack
• In-Hospital Care: may also include additional tests to determine the cause of the SCA if it is not apparent at the time of the arrest.
  
• Long-term Treatment: may include the permanent placement of an implantable cardioverter-defibrillator. This device is connected to the heart via electrical leads and implanted just under the first couple of layers of the skin. Implanted defibrillators deliver the same type of shock as an AED directly to the heart anytime an arrhythmia is detected. 

Conclusion

When comparing a heart attack to sudden cardiac arrest, the information provided here demonstrates the signs and symptoms are not only different but markedly different. Starting the correct treatments outlined above quickly is key to increasing the chances of survival for both.