Heart Attack and Sudden Cardiac Arrest

An Examination and Comparison of the Signs and Symptoms

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. 


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.

S. Joanne Dames - MD, MPH

Updated: 10/30/2018

18 Responses to “Heart Attack and Sudden Cardiac Arrest”

August 25, 2016 at 1:56 pm, Barbara Angielski said:

I have to live with the fact that when my husband suffered cardiac arrest, I didn’t do CPR while waiting for help. I now have to live with this pain the rest of my life.


September 29, 2016 at 8:17 am, AED Superstore said:

Barbara, allow us to express our condolences on your loss. Perhaps your comment will inspire others to act and learn CPR.


October 29, 2016 at 9:37 am, stephen Hayes said:

on august 23,2014, I experienced cardiac arrest. I was in Fort Meyers FLorida. I was in cadiac arrest for over 20 minutes. I was very fortunate to have a great friend, who was able to apply manual effort for over 8 minutes until the paramedics got there. I was put in an induced coma for 3days and have made a complete recovery. Ihave a defibulator.I am 64 years old.


October 29, 2016 at 9:44 am, stephen Hayes said:

The hospital that I was in is Gulf Coast Medical Center, Ft. Myers Florida.


January 18, 2017 at 11:56 am, Julia Schrandt said:

I am an instructor. Next month I will be giving CPR/AED training to middle school kids, as I have done for the last 4 years. It is difficult, some of the kids don’t have the upper body strength to perform CPR, but they try really hard. It is inspiring to me and I tell them one day they may have to help a family member.


January 19, 2017 at 9:53 am, Debbie said:

My stepson’s wife was in the hospital last night to be induced. at 3 am she went into cardiac arrest and the baby was having seizures. They had to do an emergency c-section. They are in another state. We need any and all prayers.
Thank you


December 11, 2017 at 12:14 am, Gail Bruner said:

My husband dropped to the kitchen floor at 2am March 14th 2017. Without 911 I am not sure I would have been able to save him. I have taken CPR many, many times. The 911 operator could hear me counting out loud compressions. He told me to do compressions harder and faster, he reminded me to unlock my door so EMT’s could get in and he reminded me to roll over my husband. 9 minutes of CPR, 5 shocks , a stent and 5 days in the ICU at OHSU saved his life. He is doing well at 69 years.


February 13, 2018 at 2:39 pm, Larry Elliott said:

My brother-in-law died recently while our extended family was together. My son and I performed CPR until the paramedics arrived. On their arrival they took over the care but clearly did not follow protocol. For example I requested a defibrillator which they had but could not find the stick-on leads. I tried to get them to use the paddles to make contact but they refused. When they finally found the leads and attached them it was clear that he was in V-fib. Their leader told me I was reading the rhythm upside down. WTF. It doesn’t matter.
It was horrible. What can one do if the “experts” arrive and are found to be incompetent.
Panama City, FL


February 13, 2018 at 2:58 pm, AED Superstore said:

We wish to offer our deepest condolences to you and your family. If you feel the responders acted inappropriately we would suggest you contact that agency and/or their supervisor and express your misgivings.


March 03, 2018 at 6:07 pm, MHE said:

Hi there, thanks for the great article. I have a question I’m hoping you might be able
to answer. I was wondering, What is the difference between panic
attacks and anxiety attacks? I definitely get one of the other but I’m unsure which…
I would appreciate any insight you can provide.


March 15, 2018 at 7:30 am, AED Superstore said:

Hello and thank you for your comment. Here at AED Superstore we are definitely more informed about heart-related issues than anxiety, but if you continue to have these episodes, a visit to your doctor would probably be a good idea to see if there is medication to help you control them.


September 16, 2018 at 12:50 pm, Mary Shaul said:

I’d like to know the science behind the amount of joules delivered on an AED. I know the AHA recommends 120-200 joules or higher. However, I want to know the science of the amount of joules that usually are the most effective. Where can I go to find this information out?


September 17, 2018 at 9:28 am, AED Superstore said:

Hi Mary,
We did a little digging and the best answer we found was that to terminate ventricular fibrillation, it is basically necessary to expose enough of the heart to enough current for a long enough period of time. Some AEDs use just one “dose” of joules (150j) for the initial and subsequent shocks, while others have escalating joules, meaning each shock is delivered at slightly higher doses up to the maximum currently used at 360 joules in one manufacturer. It can be assumed during the development of defibrillation, it was discovered 150 joules offered the optimum chance to reset the heart once it is in Ventricular Fibrillation. Click here for more information on the history of defibrillation


September 19, 2019 at 7:35 am, Eli Richardson said:

You listed that shortness of breathing, dizziness, and chest pain are symptoms of a heart attack. One of my uncles has chest pains last night and we didn’t know how to help him. We will immediately look for a cardiologist so he can get evaluated.


September 19, 2019 at 7:47 am, AED Superstore said:

Symptoms such as you described must always be taken seriously. It may turn out to be something simple, like heartburn, but it is always best to err on the side of caution, better to be safe than sorry, etc.


May 21, 2021 at 2:38 am, Joffer said:

Well this is awesome post and written very well. Your point of view is very good.


July 05, 2022 at 12:43 pm, KWRN said:

What does it mean when the ER doctor documents: EKG results, … two heart attacks “Probably old”


July 05, 2022 at 12:53 pm, AED Superstore said:

You should check with the doctor who made that entry.


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