The facts about cardiac arrest and resuscitation (CPR)

The American Heart Association (AHA) is having its annual Scientific Session and some of the information below is taken from presentations made there.

First, some initial information.

A cardiac arrest is not the same as a heart attack

A cardiac arrest occurs when the heart stops pumping. It may stop pumping effectively because of an arrhythmia or chaotic heart rhythm (like ventricular fibrillation.)

Therefore, in some cardiac arrests, the heart is not at a standstill. But since it isn’t pumping, blood pressure falls to zero and the patient rapidly loses consciousness. Almost always without resuscitation the patient will die. The goal of the resuscitation is to get the heart to beat rhythmically again and raise the blood pressure so that blood can perfuse vital organs like the brain, heart, liver, kidneys and others.

A heart attack occurs when the circulation though one or more coronary arteries is blocked. The part of the heart served by that artery gets starved for oxygen and nutrients and may die. A heart attack may cause a cardiac arrest.

Some basic data on cardiac arrests:

  • Almost 400,000 cardiac arrests occur in the United States per year.
  • About 88% of cardiac arrests don’t occur in a hospital, they occur at home. The life you save may be that of a spouse, parent, child, other relative, close friend or neighbor.
  • Many cardiac arrest victims don’t look ill before the arrest. They may not have any history of heart disease or previous heart attack.
  • Only 32% of out-of-hospital cardiac arrest victims receive CPR from a bystander. Because of this and other facts, only about 8% of cardiac arrest patients survive when an arrest occurs at home or in public.
  • Blacks are almost twice as likely to experience cardiac arrests in a public place as whites.
  • A survey showed that 70% of Americans feel helpless during a public cardiac arrest. The reasons are that those people either don’t know how to do CPR, or don’t do it because there has been a lapse between their training in CPR and when they are called upon to use it.
  • More men experience cardiac arrests (53%) than women (47%.)
  • Women tend to have worse outcomes than men when resuscitated.

Early initiation of CPR is important

It follows from some of the above information that if more victims of cardiac arrest received bystander CPR, more might survive. One study looked at how to do just that.

hands-only-cprEmergency Medical Service (EMS) dispatchers were told to get the caller to EMS to start CPR. The dispatchers were given instructions to read to the bystander(s) to walk them through CPR even if they had no previous training. They would read form a script and encourage the bystanders to continue CPR till EMS arrived. Though their instructions were more detailed than this, the AHA recommends the following:

Don’t be afraid; your actions can only help. If you see an unresponsive adult who is not breathing or not breathing normally, call 911 and push hard and fast on the center of the chest.

The data showed that:

  • More bystanders were willing to attempt CPR
  • Time from the receipt of the 911 call to the start of CPR decreased
  • There was an increase in survival from 7.9% to 11.2%

This last data point, that the survival rate increased from 7.9% to 11.2%, might not look like much of an increase. But remember, some of these patients may have been in cardiac arrest for some time before being discovered and there may have been nothing that could have been done to reverse that situation. Or they may have experienced cardiac arrest secondary to another fatal concurrent illness (massive stroke, aneurysm rupture, etc.) that CPR would not cure. And finally, when you do that the math, 7.9% to 11.2% is nearly a 42% increase in survival.

Cardiac arrest survival, male v. female

There are mixed results from data compiled from two European studies.

  • In a French study that reviewed data on almost 500,000 patients, researchers found that more women did not receive CPR from bystanders.
  • More women did not have a “shockable” rhythm [a “shockable” rhythm is one that may convert to a more normal, perfusing rhythm after a shock (defibrillation.) Some rhythms do not respond to shocks.]
  • Many women were older than their male counterparts and may have other associated illnesses.
  • Yet, in spite of these factors, more women who survived the resuscitation were discharged alive from the hospital than were men in similar circumstances. The reason for this is unknown.

But a Dutch study presents some different data.

Researchers identified 22,443 out-of-hospital cardiac deaths (52.8 percent male) and reviewed data on 6,038 out-of-hospital CPR attempts by emergency medical services (72.5 percent male) in the same study region, all aged over 20. They found:

  • Women have a significantly lower chance of receiving a resuscitation attempt from emergency medical personnel than men (15 percent women vs. 35 percent men).
  • Women had a significantly lower chance of successful survival after a resuscitation attempt than men (13 percent women vs. 20 percent men).
  • Women had a lower proportion of “shockable” initial heart rhythm (34 percent women vs. 49 percent men), a strong determinant of survival.

Social factors (such as older women living alone) as well as biological factors (such as women presenting with different symptoms or more heart failure as cause of the sudden cardiac arrest) may be reasons why women have less chance of receiving CPR, researchers said.

Much of the data supports information from the French study – few women have “shockable” rhythms, not as many women as men receive CPR, etc. But the Dutch study didn’t look at the number of women surviving and leaving the hospital love after treatment.

Many of the reasons for the poorer response in women may be due to social circumstances (older, living alone) or medical ones (many older people have more advanced cardiovascular disease, may have other illnesses contributing to the outcome, etc.) Thus, the lower survival rate may not be due to a gender difference. What is surprising is that, in both studies, there were fewer attempts to resuscitate women by both bystanders and by EMS personnel. That isn’t addressed by either data abstract.

The take home message

The take home message is that, in most cases:

  • Cardiac arrest is not a rare event and can often occur in public places or in the home.
  • Cardiac arrest can occur in otherwise healthy-appearing people.
  • More people survive cardiac arrest when bystanders act quickly to start CPR.
  • Bystanders should be trained (and retrained periodically) in CPR and encouraged to initiate resuscitation.

A quick word about “Hands-Only CPR.” John had mentioned to me that when he was in high school, they taught CPR with compressions and breaths. Hands-Only CPR only requires compressions. The American Heart Association has developed this technique for use in witnessed cardiac arrests, meaning you see the person collapse. Formerly, a rescuer gave two breaths and then started chest compressions after first calling 911. It’s been found that usually, in the first few minutes after a cardiac arrest, the victim has enough oxygen in his lungs and blood to supply the tissues without having someone breathe for him.

So, if an adult or teen is seen to collapse, hands-only CPR is appropriate.

But, for infants, children, someone with known breathing problems, drowning victims or an unwitnessd arrest, standard CPR (calling 911, giving breaths alternating with compressions) is preferred.

Rather than get bogged down in the details, use this as your general rule: Hands-only CPR is for a witnessed arrest in an adult or teen. Others will probably need CPR.

To see or learn “Hands-Only CPR,” find CPR classes, get additional information, read stories of resuscitation survivors, and more, check out these videos from the American Heart Association. It’s surprising how easy hands-only CPR really is:


Mark Thoma, MD, is a physician who did his residency in internal medicine. Mark has a long history of social activism, and was an early technogeek, and science junkie, after evolving through his nerd phase. Favorite quote: “The most exciting phrase to hear in science... is not 'Eureka!' (I found it!) but 'That's funny.'” - Isaac Asimov

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  • Captrwright

    Hey Nicho, if you not sure, why not give it a try. A surviving victim would certainly appreciate it.

  • Michael Charles

    How about looking at it as if your intervention is part of God/Jesus’ plan to test you. Whether the victim survives or not IS up to God. But the test is of you. Do your best.

  • super

    If you are going to discuss CPR, please include a section on neurological outcomes- survival does not necessarily mean neurologically intact.

  • nicho

    God wouldn’t like that.

  • pricknick

    No medications of any kind for you.

  • nicho

    I’m not sure we should be playing God. If Jesus calls someone safely home, who are we to interfere with his plan?

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